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J.P. Magué & B. Ménard

[1]
Title: Atomic data and spectral modeling constraints from high-resolution X-ray observations of the Perseus cluster with Hitomi
Comments: 46 pages, 25 figures, 11 tables. Accepted for publication in PASJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The Hitomi SXS spectrum of the Perseus cluster, with $\sim$5 eV resolution in the 2-9 keV band, offers an unprecedented benchmark of the atomic modeling and database for hot collisional plasmas. It reveals both successes and challenges of the current atomic codes. The latest versions of AtomDB/APEC (3.0.8), SPEX (3.03.00), and CHIANTI (8.0) all provide reasonable fits to the broad-band spectrum, and are in close agreement on best-fit temperature, emission measure, and abundances of a few elements such as Ni. For the Fe abundance, the APEC and SPEX measurements differ by 16%, which is 17 times higher than the statistical uncertainty. This is mostly attributed to the differences in adopted collisional excitation and dielectronic recombination rates of the strongest emission lines. We further investigate and compare the sensitivity of the derived physical parameters to the astrophysical source modeling and instrumental effects. The Hitomi results show that an accurate atomic code is as important as the astrophysical modeling and instrumental calibration aspects. Substantial updates of atomic databases and targeted laboratory measurements are needed to get the current codes ready for the data from the next Hitomi-level mission.

[2]
Title: Stellar Population Synthesis of star forming clumps in galaxy pairs and non-interacting spiral galaxies
Comments: Accepted for publication in ApJS. 20 pages, 10 figures, 6 tables
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We have identified 1027 star forming complexes in a sample of 46 galaxies from the Spirals, Bridges, and Tails (SB&T) sample of interacting galaxies, and 693 star forming complexes in a sample of 38 non-interacting spiral (NIS) galaxies in $8\rm{\mu m}$ observations from the Spitzer Infrared Array Camera. We have used archival multi-wavelength UV-to IR observations to fit the observed spectral energy distribution (SED) of our clumps with the Code Investigating GALaxy Emission (CIGALE) using a double exponentially declined star formation history (SFH). We derive SFRs, stellar masses, ages and fractions of the most recent burst, dust attenuation, and fractional emission due to an AGN for these clumps. The resolved star formation main sequence holds on 2.5kpc scales, although it does not hold on 1kpc scales. We analyzed the relation between SFR, stellar mass, and age of the recent burst in the SB&T and NIS samples, and we found that the SFR per stellar mass is higher in the SB&T galaxies, and the clumps are younger in the galaxy pairs. We analyzed the SFR radial profile and found that SFR is enhanced through the disk and in the tidal features relative to normal spirals.

[3]
Title: The multiplicity and anisotropy of galactic satellite accretion
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We study the incidence of group and filamentary dwarf galaxy accretion into Milky Way (MW) mass haloes using two types of hydrodynamical simulations: EAGLE, which resolves a large cosmological volume, and the AURIGA suite, which are very high resolution zoom-in simulations of individual MW-sized haloes. The present-day 11 most massive satellites are predominantly (75%) accreted in single events, 14% in pairs and 6% in triplets, with higher group multiplicities being unlikely. Group accretion becomes more common for fainter satellites, with 60% of the top 50 satellites accreted singly, 12% in pairs, and 28% in richer groups. A group similar in stellar mass to the Large Magellanic Cloud (LMC) would bring on average 15 members with stellar mass larger than $10^4{~\rm M_\odot}$. Half of the top 11 satellites are accreted along the two richest filaments. The accretion of dwarf galaxies is highly anisotropic, taking place preferentially perpendicular to the halo minor axis, and, within this plane, preferentially along the halo major axis. The satellite entry points tend to be aligned with the present-day central galaxy disc and satellite plane, but to a lesser extent than with the halo shape. Dwarfs accreted in groups or along the richest filament have entry points that show an even larger degree of alignment with the host halo than the full satellite population. We also find that having most satellites accreted as a single group or along a single filament is unlikely to explain the MW disc of satellites.

[4]
Title: Intra-cluster Globular Clusters in a Simulated Galaxy Cluster
Comments: accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Using a cosmological dark matter simulation of a galaxy-cluster halo, we follow the temporal evolution of its globular cluster population. To mimic the red and blue globular cluster populations, we select at high redshift $(z\sim 1)$ two sets of particles from individual galactic halos constrained by the fact that, at redshift $z=0$, they have density profiles similar to observed ones. At redshift $z=0$, approximately 60\% of our selected globular clusters were removed from their original halos building up the intra-cluster globular cluster population, while the remaining 40\% are still gravitationally bound to their original galactic halos. Since the blue population is more extended than the red one, the intra-cluster globular cluster population is dominated by blue globular clusters, with a relative fraction that grows from 60\% at redshift $z=0$ up to 83\% for redshift $z\sim 2$. In agreement with observational results for the Virgo galaxy cluster, the blue intra-cluster globular cluster population is more spatially extended than the red one, pointing to a tidally disrupted origin.

[5]
Title: Wandering off the centre: A characterisation of the random motion of intermediate-mass black holes in star clusters
Comments: 14 pages, 9 figures, 2 tables; accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Despite recent observational efforts, unequivocal signs for the presence of intermediate-mass black holes (IMBHs) in globular clusters (GCs) have not been found yet. Especially when the presence of IMBHs is constrained through dynamical modeling of stellar kinematics, it is fundamental to account for the displacement that the IMBH might have with respect to the GC centre. In this paper we analyse the IMBH wandering around the stellar density centre using a set of realistic direct N-body simulations of star cluster evolution. Guided by the simulation results, we develop a basic yet accurate model that can be used to estimate the average IMBH radial displacement ($\left<r_\mathrm{bh}\right>$) in terms of structural quantities as the core radius ($r_\mathrm{c}$), mass ($M_\mathrm{c}$), and velocity dispersion ($\sigma_\mathrm{c}$), in addition to the average stellar mass ($m_\mathrm{c}$) and the IMBH mass ($M_\mathrm{bh}$). The model can be expressed by the equation $\left<r_\mathrm{bh}\right>/r_\mathrm{c}=A(m_\mathrm{c}/M_\mathrm{bh})^\alpha[\sigma_\mathrm{c}^2r_\mathrm{c}/(GM_\mathrm{c})]^\beta$, in which the free parameters $A,\alpha,\beta$ are calculated through comparison with the numerical results on the IMBH displacement. The model is then applied to Galactic GCs, finding that for an IMBH mass equal to 0.1% of the GC mass, the typical expected displacement of a putative IMBH is around $1''$ for most Galactic GCs, but IMBHs can wander to larger angular distances in some objects, including a prediction of a $2.5''$ displacement for NGC 5139 ($\omega$ Cen), and $>10''$ for NGC 5053, NGC 6366 and ARP2.

[6]
Title: $M_*/L$ gradients driven by IMF variation: Large impact on dynamical stellar mass estimates
Comments: 12 pages, 6 figures, submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Within a galaxy the stellar mass-to-light ratio $\Upsilon_*$ is not constant. We show that ignoring $\Upsilon_*$ gradients can have a more dramatic effect on dynamical ($M_*^{\rm dyn}$) compared to stellar population ($M_*^{\rm SP}$) based estimates of early-type galaxy stellar masses, because $M_*^{\rm dyn}$ is usually calibrated using the velocity dispersion measured in the central regions. If $\Upsilon_*$ is greater there, then ignoring the gradient will lead to an overestimate of $M_*^{\rm dyn}$. Spatially resolved kinematics of nearby early-type galaxies suggests that these gradients are driven by gradients in the initial mass function (IMF). Accounting for recent estimates of the IMF-driven $\Upsilon_*$ gradient reduces $M_*^{\rm dyn}$ substantially ($\sim$ a factor of two), and may be accompanied by a (smaller) change in $M_*^{\rm SP}$. Our results suggest that $M_*^{\rm dyn}$ estimates in the literature should be revised downwards, rather than revising $M_*^{\rm SP}$ estimates upwards. This has three consequences. First, if gradients in $\Upsilon_*$ are present, then $M_*^{\rm dyn}$ cannot be estimated independently of stellar population synthesis models. Second, accounting for $\Upsilon_*$ gradients changes the slope of the stellar mass function $\phi(M_*^{\rm dyn})$, and reduces the associated stellar mass density, especially at high masses. Third, if gradients are stronger in more massive galaxies, then accounting for this reduces the slope of the correlation between the ratio of the dynamical and stellar population mass estimates of a galaxy with its velocity dispersion. These conclusions potentially impact estimates of the need for feedback and adiabatic contraction, so our results highlight the importance of measurements of $\Upsilon_*$ gradients in larger samples.

[7]
Title: Prospects for detecting gravitational waves at 5 Hz with ground-based detectors
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

We propose an upgrade of Advanced LIGO (aLIGO), named LIGO-LF, that focuses on improving the sensitivity in the 5-30 Hz low-frequency band, and we explore the upgrade's astrophysical applications. We present a comprehensive study of the detector's technical noises, and show that with the new technologies such as interferometrically-sensed seismometers and balanced-homodyne readout, LIGO-LF can reach the fundamental limits set by quantum and thermal noises down to 5 Hz. These technologies are also directly applicable to the future generation of detectors. LIGO-LF can observe a rich array of astrophysical sources such as binary black holes with total mass up to 2000 M_\odot. The horizon distance of a single LIGO-LF detector will be z ~ 6, greatly exceeding aLIGO's reach. Additionally, for a given source the chirp mass and total mass can be constrained 2 times better, and the effective spin 3-5 times better, than aLIGO. The total number of detected merging black holes will increase by a factor of 16 compared with aLIGO. Meanwhile, LIGO-LF will also significantly enhance the probability of detecting other astrophysical phenomena including the gravitational memory effects and the neutron star r-mode resonances.

[8]
Title: Exploring The Effects Of Disk Thickness On The Black Hole Reflection Spectrum
Comments: 19 pages, 10 figures, Submitted for publication in ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

The relativistically-broadened reflection spectrum, observed in both AGN and X-ray binaries, has proven to be a powerful probe of the properties of black holes and the environments in which they reside. Being emitted from the inner-most regions of the accretion disk, this X-ray spectral component carries with it information not only about the plasma that resides in these extreme conditions, but also the black hole spin, a marker of the formation and accretion history of these objects. The models currently used to interpret the reflection spectrum are often simplistic, however, approximating the disk as an infinitely thin, optically thick plane of material orbiting in circular Keplerian orbits around the central object. Using a new relativistic ray tracing suite (Fenrir) that allows for more complex disk approximations, we examine the effects that disk thickness may have on the reflection spectrum. We find that finite disk thickness can have a variety of effects on the reflection spectrum, including a truncation of the blue wing (from self-shadowing of the accretion disk) and an enhancement of the red wing (from the irradiation of the central 'eye wall' of the inner disk). We make a first estimate on the systematic errors on black hole spin and height that may result from neglecting these effects.

[9]
Title: Astrometry with the WFIRST Wide-Field Imager
Authors: The WFIRST Astrometry Working Group: Robyn E. Sanderson (1), Andrea Bellini (2), Stefano Casertano (2), Jessica R. Lu (3), Peter Melchior (4), David Bennett (5), Michael Shao (6), Jason Rhodes (6), Sangeeta Malhotra (5), Scott Gaudi (7), Michael Fall (2), Ed Nelan (2), Puragra Guhathakurta (8), Jay Anderson (2), Shirley Ho (3 and 9), Mattia Libralato (2) ((1) TAPIR, California Institute of Technology, (2) Space Telescope Science Institute, (3) Department of Astronomy, University of California, Berkeley, (4) Department of Astrophysical Sciences, Princeton University, (5) Astrophysics Science Division, NASA Goddard Space Flight Center, (6) Jet Propulsion Laboratory, California Institute of Technology, (7) Department of Astronomy, Ohio State University, (8) University of California Santa Cruz, (9) Department of Physics, University of California, Berkeley)
Comments: 25 pages, 15 figures; submitted to PASP
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

The Wide-Field InfraRed Space Telescope (WFIRST) will be capable of delivering precise astrometry for faint sources over the enormous field of view of its main camera, the Wide-Field Imager (WFI). This unprecedented combination will be transformative for the many scientific questions that require precise positions, distances, and velocities of stars. We describe the expectations for the astrometric precision of the WFIRST WFI in different scenarios, illustrate how a broad range of science cases will see significant advances with such data, and identify aspects of WFIRST's design where small adjustments could greatly improve its power as an astrometric instrument.

[10]
Title: Are ultracompact minihalos really ultracompact?
Comments: 7 pages, 4 figures; to be submitted to PRD
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Ultracompact minihalos (UCMHs) have emerged as a valuable probe of the primordial power spectrum of density fluctuations at small scales. UCMHs are expected to form at early times in regions with $\delta\rho/\rho \gtrsim 10^{-3}$, and they are theorized to possess an extremely compact $\rho\propto r^{-9/4}$ radial density profile, which enhances their observable signatures. Non-observation of UCMHs can thus constrain the primordial power spectrum. Using N-body simulations to study the collapse of extreme density peaks at $z \simeq 1000$, we show that UCMHs forming under realistic conditions do not develop the $\rho\propto r^{-9/4}$ profile, and instead develop either $\rho\propto r^{-3/2}$ or $\rho\propto r^{-1}$ inner density profiles depending on the shape of the power spectrum. We also demonstrate via idealized simulations that self-similarity -- the absence of a scale length -- is necessary to produce a halo with the $\rho\propto r^{-9/4}$ profile, and we argue that this implies such halos cannot form from a Gaussian primordial density field. Prior constraints derived from UCMH non-observation must be reworked in light of this discovery. Although the shallower density profile reduces UCMH visibility, our findings reduce their signal by as little as $\mathcal O(10^{-2})$ while allowing later-forming halos to be considered, which suggests that new constraints could be significantly stronger.

[11]
Title: Interaction in the dark sector: a Bayesian analysis with latest observations
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

By combining cosmological probes at low, intermediate and high redshifts, we investigate the observational viability of a class of models with interaction in the dark sector. We perform a Bayesian analysis using the latest data sets of type Ia supernovae, baryon acoustic oscillations, the angular acoustic scale of the cosmic microwave background, and measurements of the expansion rate. When combined with the current measurement of the local expansion rate obtained by the Hubble Space Telescope, we find that these observations provide evidence in favour of interacting models with respect to the standard cosmology.

[12]
Title: Gravity mode offset and properties of the evanescent zone in red-giant stars
Comments: accepted for publication in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The wealth of asteroseismic data for red-giant stars and the precision with which these data have been observed over the last decade calls for investigations to further understand the internal structures of these stars. The aim of this work is to validate a method to measure the underlying period spacing, coupling term and mode offset of pure gravity modes that are present in the deep interiors of red-giant stars. We subsequently investigate the physical conditions of the evanescent zone between the gravity mode cavity and the pressure mode cavity. We implement an alternative mathematical description to analyse observational data and to extract the underlying physical parameters that determine the frequencies of mixed modes. This description takes the radial order of the modes explicitly into account, which reduces its sensitivity to aliases. Additionally, and for the first time, this method allows us to constrain the gravity mode offset for red-giant stars. We determine the period spacing and the coupling term for the dipole modes within a few percent of literature values. Additionally, we find that the gravity mode offset varies on a star by star basis and should not be kept fixed in the analysis. Furthermore, we find that the coupling factor is logarithmically related to the physical width of the evanescent region normalised by the radius at which the evanescent zone is located. Finally, the local density contrast at the edge of the core of red giant branch models shows a tentative correlation with the offset. (abstract abriged)

[13]
Title: ATCA observations of the MACS-Planck Radio Halo Cluster Project II. Radio observations of an intermediate redshift cluster sample
Comments: 12 pages, 7 figures, accepted for publication in A&A
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

A fraction of galaxy clusters host diffuse radio sources whose origins are investigated through multi-wavelength studies of cluster samples. We investigate the presence of diffuse radio emission in a sample of seven galaxy clusters in the largely unexplored intermediate redshift range (0.3 < z < 0.44). In search of diffuse emission, deep radio imaging of the clusters are presented from wide band (1.1-3.1 GHz), full resolution ($\sim$ 5 arcsec) observations with the Australia Telescope Compact Array (ATCA). The visibilities were also imaged at lower resolution after point source modelling and subtraction and after a taper was applied to achieve better sensitivity to low surface brightness diffuse radio emission. In case of non-detection of diffuse sources, we set upper limits for the radio power of injected diffuse radio sources in the field of our observations. Furthermore, we discuss the dynamical state of the observed clusters based on an X-ray morphological analysis with XMM-Newton. We detect a giant radio halo in PSZ2 G284.97-23.69 (z=0.39) and a possible diffuse source in the nearly relaxed cluster PSZ2 G262.73-40.92 (z=0.421). Our sample contains three highly disturbed massive clusters without clear traces of diffuse emission at the observed frequencies. We were able to inject modelled radio halos with low values of total flux density to set upper detection limits; however, with our high-frequency observations we cannot exclude the presence of RH in these systems because of the sensitivity of our observations in combination with the high z of the observed clusters.

[14]
Title: The Photon in Dense Nuclear Matter I: Random Phase Approximation
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Other Condensed Matter (cond-mat.other); Nuclear Theory (nucl-th)

We present a comprehensive and pedagogic discussion of the properties of photons in cold and dense nuclear matter based on the resummed one-loop photon self energy. Correlations between electrons, muons, protons and neutrons in beta equilibrium that arise due to electromagnetic and strong interactions are consistently taken into account within the random phase approximation. Screening effects and damping as well as collective excitations are systematically studied in a fully relativistic setup. Our study is relevant to linear response theory of dense nuclear matter, calculations of transport properties of cold dense matter and to investigations of the production and propagation of hypothetical vector bosons such as the dark photons.

[15]
Title: Quasi-Periodic Behavior of Mini-Disks in Binary Black Holes Approaching Merger
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc)

We present the first magnetohydrodynamic simulation in which a circumbinary disk around a relativistic binary black hole feeds mass to individual accretion disks ("mini-disks") around each black hole. Mass flow through the accretion streams linking the circumbinary disk to the mini-disks is modulated quasi-periodically by the streams' interaction with a nonlinear $m=1$ density feature, or "lump", at the inner edge of the circumbinary disk: the stream supplying each mini-disk comes into phase with the lump at a frequency $0.74$ times the binary orbital frequency. Because the binary is relativistic, the tidal truncation radii of the mini-disks are not much larger than their innermost stable circular orbits; consequently, the mini-disks' inflow times are shorter than the conventional estimate and are comparable to the stream modulation period. As a result, the mini-disks are always in inflow disequilibrium, with their masses and spiral density wave structures responding to the stream's quasi-periodic modulation. The fluctuations in each mini-disk's mass are so large that as much as $75\%$ of the total mini-disk mass can be contained within a single mini-disk. Such quasi-periodic modulation of the mini-disk structure may introduce distinctive time-dependent features in the binary's electromagnetic emission.

[16]
Title: Exoplanet Radius Gap Dependence on Host Star Type
Comments: 2pages, 1 figure, RNAAS 2017
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Exoplanets smaller than Neptune are numerous, but the nature of the planet populations in the 1-4 Earth radii range remains a mystery. The complete Kepler sample of Q1-Q17 exoplanet candidates shows a radius gap at ~ 2 Earth radii, as reported by us in January 2017 in LPSC conference abstract #1576 (Zeng et al. 2017). A careful analysis of Kepler host stars spectroscopy by the CKS survey allowed Fulton et al. (2017) in March 2017 to unambiguously show this radius gap. The cause of this gap is still under discussion (Ginzburg et al. 2017; Lehmer & Catling 2017; Owen & Wu 2017). Here we add to our original analysis the dependence of the radius gap on host star type.

[17]
Title: Multi-wavelength scaling relations in galaxy groups: a detailed comparison of GAMA and KiDS observations to BAHAMAS simulations
Comments: 18 pages, 11 figures, submitted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We study the scaling relations between the baryonic content and total mass of groups of galaxies, as these systems provide a unique way to examine the role of non-gravitational processes in structure formation. Using Planck and ROSAT data, we conduct detailed comparisons of the stacked thermal Sunyaev-Zel'dovich (tSZ) effect and X-ray scaling relations of galaxy groups found in the the Galaxy And Mass Assembly (GAMA) survey and the BAHAMAS hydrodynamical simulation. We use weak gravitational lensing data from the Kilo Degree Survey (KiDS) to determine the average halo mass of the studied systems. We analyse the simulation in the same way, using realistic weak lensing, X-ray, and tSZ synthetic observations. Furthermore, to keep selection biases under control, we employ exactly the same galaxy selection and group identification procedures to the observations and simulation. Applying this careful comparison, we find that the simulations are in agreement with the observations, particularly with regards to the scaling relations of the lensing and tSZ results. This finding demonstrates that hydrodynamical simulation have reached the level of realism that is required to interpret observational survey data and study the baryon physics within dark matter haloes, where analytical modelling is challenging. Finally, using simulated data, we demonstrate that our observational processing of the X-ray and tSZ signals is free of significant biases. We find that our optical group selection procedure has, however, some room for improvement.

[18]
Title: Thermodynamic Profiles of Galaxy Clusters from a Joint X-ray/SZ Analysis
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We jointly analyze Bolocam Sunyaev-Zeldovich (SZ) effect and Chandra X-ray data for a set of 45 clusters to derive gas density and temperature profiles without using spectroscopic information. The sample spans the mass and redshift range $3 \times 10^{14} M_{\odot} \le M_{500} \le 25 \times 10^{14} M_{\odot}$ and $0.15\le z \le 0.89$. We define cool-core (CC) and non-cool core (NCC) subsamples based on the central X-ray luminosity, and 17/45 clusters are classified as CC. In general, the profiles derived from our analysis are found to be in good agreement with previous analyses, and profile constraints beyond $r_{500}$ are obtained for 34/45 clusters. In approximately 30% of the CC clusters our analysis shows a central temperature drop with a statistical significance of $>3\sigma$; this modest detection fraction is due mainly to a combination of coarse angular resolution and modest S/N in the SZ data. Most clusters are consistent with an isothermal profile at the largest radii near $r_{500}$, although 9/45 show a significant temperature decrease with increasing radius. The sample mean density profile is in good agreement with previous studies, and shows a minimum intrinsic scatter of approximately 10% near $0.5 \times r_{500}$. The sample mean temperature profile is consistent with isothermal, and has an intrinsic scatter of approximately 50% independent of radius. This scatter is significantly higher compared to earlier X-ray-only studies, which find intrinsic scatters near 10%, likely due to a combination of unaccounted for non-idealities in the SZ noise, projection effects, and sample selection.

[19]
Title: Supernova Ejecta in Ocean Cores Used as Time Constraints for Nearby Stellar Groups
Comments: 9 Pages, 3 figures, 8 tables
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Evidence of a supernova event, discussed in Wallner et al., was discovered in the deep-sea crusts with two signals dating back to 2-3 and 7-9 Myr ago. In this contribution, we place constraints on the birth-site of the supernova progenitors from the ejecta timeline, the initial mass function, and the ages of nearby stellar groups. We investigated the Scorpius-Centaurus OB Association, the nearest site of recent massive star formation, and the moving group Tucana-Horologium. Using the known stellar mass of the remaining massive stars within these subgroups and factoring in travel time for the ejecta, we have constrained the ages and masses of the supernova progenitors by using the initial mass function and then compared the results to the canonical ages of each subgroup. Our results identify the Upper Scorpius and Lower Centaurus-Crux subgroups as unlikely birth-sites for these supernovae. We find that Tucana-Horologium is the likely birth-site of the supernova 7-9 Myr ago and Upper Centaurus-Lupus is the likely birth-site for the supernova 2-3 Myr ago.

[20]
Title: An Optical and Infrared Time-Domain Study of the Supergiant Fast X-ray Transient Candidate IC 10 X-2
Comments: 15 pages, 4 figures. Submitted to ApJ on Sep 26 2017
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

We present an optical and infrared (IR) study of IC 10 X-2, a high-mass X-ray binary in the galaxy IC 10. Previous optical and X-ray studies suggest X-2 is a Supergiant Fast X-ray Transient: a large-amplitude (factor of $\sim$ 100), short-duration (hours to weeks) X-ray outburst on 2010 May 21. We analyze R- and g-band light curves of X-2 from the intermediate Palomar Transient Factory taken between 2013 July 15 and 2017 Feb 14 show high-amplitude ($\gtrsim$ 1 mag), short-duration ($\lesssim8$ d) flares and dips ($\gtrsim$ 0.5 mag). Near-IR spectroscopy of X-2 from Palomar/TripleSpec show He I, Paschen-$\gamma$, and Paschen-$\beta$ emission lines with similar shapes and amplitudes as those of luminous blue variables (LBVs) and LBV candidates (LBVc). Mid-IR colors and magnitudes from Spitzer/IRAC photometry of X-2 resemble those of known LBV/LBVcs. We suggest that the stellar companion in X-2 is an LBV/LBVc and discuss possible origins of the optical flares. Dips in the optical light curve are indicative of eclipses from optically thick clumps formed in the winds of the stellar counterpart. Given the constraints on the flare duration ($0.02 - 0.8$ d) and the time between flares ($15.1\pm7.8$ d), we estimate the clump volume filling factor in the stellar winds, $f_V$, to be $0.01 < f_V < 0.71$, which overlaps with values measured from massive star winds. In X-2, we interpret the origin of the optical flares as the accretion of clumps formed in the winds of an LBV/LBVc onto the compact object.

[21]
Title: Properties of Two-Temperature Dissipative Accretion Flow Around Black Holes
Comments: 15 pages, 13 figures, accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We study the properties of two-temperature accretion flow around a non-rotating black hole in presence of various dissipative processes where pseudo-Newtonian potential is adopted to mimic the effect of general relativity. The flow encounters energy loss by means of radiative processes acted on the electrons and at the same time, flow heats up as a consequence of viscous heating effective on ions. We assumed that the flow is exposed with the stochastic magnetic fields which leads to Synchrotron emission of electrons and these emissions are further strengthen by Compton scattering. We obtain the two-temperature global accretion solutions in terms of dissipation parameters, namely, viscosity ($\alpha$) and accretion rate (${\dot m}$), and find for the first time in the literature that such solutions may contain standing shock waves. Solutions of this kind are multi-transonic in nature as they simultaneously pass through both inner critical point ($x_{\rm in}$) and outer critical point ($x_{\rm out}$) before crossing the black hole horizon. We calculate the properties of shock induced global accretion solutions in terms of the flow parameters. We further show that two-temperature shocked accretion flow is not a discrete solution, instead such solution exists for wide range of flow parameters. We identify the effective domain of the parameter space for standing shock and observe that parameter space shrinks as the dissipation is increased. Since the post-shock region is hotter due to the effect of shock compression, it naturally emits hard X-rays and therefore, the two-temperature shocked accretion solution has the potential to explain the spectral properties of the black hole sources.

[22]
Title: Estimation of the gravitational wave polarizations from a non template search
Authors: I. Di Palma, M. Drago
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Gravitational wave astronomy is just beginning, after the recent success of the four direct detections of binary black hole (BBH) mergers, the first observation from a binary neutron star inspiral and with the expectation of many more events to come. Given the possibility to detect waves from not perfectly modeled astrophysical processes, it is fundamental to be ready to calculate the polarization waveforms in the case of searches using non-template algorithms. In such case, the waveform polarizations are the only quantities that contain direct information about the generating process. We present the performance of a new valuable tool to estimate the inverse solution of gravitational wave transient signals, starting from the analysis of the signal properties of a non-template algorithm that is open to a wider class of gravitational signals not covered by template algorithms. We highlight the contributions to the wave polarization associated with the detector response, the sky localization and the polarization angle of the source. In this paper we present the performances of such method and its implications by using two main classes of transient signals, resembling the limiting case for most simple and complicated morphologies. Performances are encouraging, for the tested waveforms: the correlation between the original and the reconstructed waveforms spans from better than 80% for simple morphologies to better than 50% for complicated ones. For a not-template search this results can be considered satisfactory to reconstruct the astrophysical progenitor.

[23]
Title: Data release of UV to submm broadband fluxes for simulated galaxies from the EAGLE project
Comments: 20 pages, 10 figures, accepted for publication in ApJS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present dust-attenuated and dust emission fluxes for sufficiently resolved galaxies in the EAGLE suite of cosmological hydrodynamical simulations, calculated with the SKIRT radiative transfer code. The post-processing procedure includes specific components for star formation regions, stellar sources, and diffuse dust, and takes into account stochastic heating of dust grains to obtain realistic broad-band fluxes in the wavelength range from ultraviolet to sub-millimeter. The mock survey includes nearly half a million simulated galaxies with stellar masses above 10^8.5 solar masses across six EAGLE models. About two thirds of these galaxies, residing in 23 redshift bins up to z=6, have a sufficiently resolved metallic gas distribution to derive meaningful dust attenuation and emission, with the important caveat that the same dust properties were used at all redshifts. These newly released data complement the already publicly available information about the EAGLE galaxies, which includes intrinsic properties derived by aggregating the properties of the smoothed particles representing matter in the simulation. We further provide an open source framework of Python procedures for post-processing simulated galaxies with the radiative transfer code SKIRT. The framework allows any third party to calculate synthetic images, SEDs, and broadband fluxes for EAGLE galaxies, taking into account the effects of dust attenuation and emission.

[24]
Title: Nonradial and nonpolytropic astrophysical outflows. X. Relativistic MHD rotating spine jets in Kerr metric
Comments: Accepted for publication in Astronomy and Astrophysics
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

High resolution radio imaging of AGN have revealed that some sources present motion of superluminal knots and transverse stratification of their jet. Recent observational projects have provided new observational constraints on the central region of rotating black holes in AGN, suggesting that there is an inner- or spine-jet surrounded by a disk wind. This relativistic spine-jet is likely to be composed of electron - positron pairs extracting energy from the black hole. In this article we present an extension and generalization to relativistic jets in Kerr metric of the meridional self similar mechanism. We aim at modeling the inner spine-jet of AGN as the relativistic light outflow emerging from a spherical corona surrounding a Kerr black hole. The model is built by expanding the metric and the forces with colatitude to first order in the magnetic flux function. Conversely to previous models, effects of the light cylinder are not neglected. Solutions with high Lorentz factor are obtained and provide spine-jet models up to the polar axis. As in previous publications, we calculate the magnetic collimation efficiency parameter, which measures the variation of the available energy across the field lines. This collimation efficiency is an integral of the model, generalizing to Kerr metric the classical magnetic rotator efficiency criterion. We study the variation of the magnetic efficiency and acceleration with the spin of the black hole and show their high sensitivity to this integral. These new solutions model collimated or radial, relativistic or ultra-relativistic outflows. We discuss the relevance of our solutions to model the M87 spine-jet. We study the efficiency of the central black hole spin to collimate a spine-jet and show that the jet power is of the same order with that determined by numerical simulations.

[25]
Title: Joint Fit of Warm Absorbers in COS & HETG Spectra of NGC 3783
Journal-ref: Research in Astronomy and Astrophysics, Volume 17, Issue 9, article id. 095 (2017)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Warm Absorbers (WAs), as an important form of AGN outflows, show absorption in both UV and X-ray band. Using XSTAR generated photoionization models, for the first time we present a joint fit to the simultaneous observations of HST/COS and Chandra/HETG on NGC 3783. Totally five. As explain well all absorption features from the AGN outflows, which spread a wide range of ionization parameter log{\xi} from 0.6 to 3.8, column density logNH from 19.5 to 22.3 cm^{-2}, velocity v from 380 to 1060 km s^{-1}, and covering factors from 0.33 to 0.75, respectively. Not all the five WAs are consistent in pressure. Two of them are likely different parts of the same absorbing gas, and two of the other WAs may be smaller discrete clouds that are blown out from the inner region of the torus at different periods. The five WAs suggest a total mass outflowing rate within the range of 0.22-4.1 solar mass per year.

[26]
Title: Gamma-ray emission from the black hole's vicinity in AGN
Comments: Talk presented at the 7th Fermi Symposium, Garmisch-Partenkirchen, October 2017
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Non-thermal magnetospheric processes in the vicinity of supermassive black holes have attracted particular attention in recent times. Gap-type particle acceleration accompanied by curvature and Inverse Compton radiation could in principle lead to variable gamma-ray emission that may be detectable with current instruments. We shortly comment on the occurrence of magnetospheric gaps and the realisation of different potentials. The detection of rapid variability becomes most instructive by imposing a constraint on possible gap sizes, thereby limiting extractable gap powers and allowing to assess the plausibility of a magnetospheric origin. The relevance of this is discussed for the radio galaxies Cen A, M87 and IC310. The detection of magnetospheric gamma-ray emission generally allows for a sensitive probe of the near-black-hole region and is thus of prime interest for advancing our understanding of the (astro)physics of extreme environments

[27]
Title: On fragmentation of turbulent self-gravitating discs in the long cooling time regime
Authors: Ken Rice (1), Sergei Nayakshin (2) ((1) University of Edinburgh, (2) University of Leicester)
Comments: 12 pages, 12 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

It has recently been suggested that in the presence of driven turbulence discs may be much less stable against gravitational collapse than their non turbulent analogs, due to stochastic density fluctuations in turbulent flows. This mode of fragmentation would be especially important for gas giant planet formation. Here we argue, however, that stochastic density fluctuations due to turbulence do not enhance gravitational instability and disc fragmentation in the long cooling time limit appropriate for planet forming discs. These fluctuations evolve adiabatically and dissipate away by decompression faster than they could collapse. We investigate these issues numerically in 2D via shearing box simulations with driven turbulence and also in 3D with a model of instantaneously applied turbulent velocity kicks. In the former setting turbulent driving leads to additional disc heating that tends to make discs more, rather than less, stable to gravitational instability. In the latter setting, the formation of high density regions due to convergent velocity kicks is found to be quickly followed by decompression, as expected. We therefore conclude that driven turbulence does not promote disc fragmentation in protoplanetary discs and instead tends to make the discs more stable. We also argue that sustaining supersonic turbulence is very difficult in discs that cool slowly.

[28]
Title: A changing wind collision
Authors: Yael Naze (1), Gloria Koenigsberger (2), Julian M. Pittard (3), Elliot Ross Parkin, Gregor Rauw (1), Michael F. Corcoran (4), D. John Hillier (5) ((1) ULg, (2) UNAM, (3) Univ. of Leeds, (4) GSFC, (5) PITT PACC)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

We report on the first detection of a global change in the X-ray emitting properties of a wind-wind collision, thanks to XMM-Newton observations of the massive SMC system HD5980. While its lightcurve had remained unchanged between 2000 and 2005, the X-ray flux has now increased by a factor of ~2.5, and slightly hardened. The new observations also extend the observational coverage over the entire orbit, pinpointing the lightcurve shape. It has not varied much despite the large overall brightening, and a tight correlation of fluxes with orbital separation is found, without any hysteresis effect. Moreover, the absence of eclipses and of absorption effects related to orientation suggests a large size for the X-ray emitting region. Simple analytical models of the wind-wind collision, considering the varying wind properties of the eruptive component in HD5980, are able to reproduce the recent hardening and the flux-separation relationship, at least qualitatively, but they predict a hardening at apastron and little change in mean flux, contrary to observations. The brightness change could then possibly be related to a recently theorized phenomenon linked to the varying strength of thin-shell instabilities in shocked wind regions.

[29]
Title: Interior Structures and Tidal Heating in the TRAPPIST-1 Planets
Comments: 34 pages, 3 tables, 4 figures. Accepted for publication in Astronomy & Astrophysics
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

With seven planets, the TRAPPIST-1 system has the largest number of exoplanets discovered in a single system so far. The system is of astrobiological interest, because three of its planets orbit in the habitable zone of the ultracool M dwarf. Assuming the planets are composed of non-compressible iron, rock, and H$_2$O, we determine possible interior structures for each planet. To determine how much tidal heat may be dissipated within each planet, we construct a tidal heat generation model using a single uniform viscosity and rigidity for each planet based on the planet's composition. With the exception of TRAPPIST-1c, all seven of the planets have densities low enough to indicate the presence of significant H$_2$O in some form. Planets b and c experience enough heating from planetary tides to maintain magma oceans in their rock mantles; planet c may have eruptions of silicate magma on its surface, which may be detectable with next-generation instrumentation. Tidal heat fluxes on planets d, e, and f are lower, but are still twenty times higher than Earth's mean heat flow. Planets d and e are the most likely to be habitable. Planet d avoids the runaway greenhouse state if its albedo is $\gtrsim$ 0.3. Determining the planet's masses within $\sim0.1$ to 0.5 Earth masses would confirm or rule out the presence of H$_2$O and/or iron in each planet, and permit detailed models of heat production and transport in each planet. Understanding the geodynamics of ice-rich planets f, g, and h requires more sophisticated modeling that can self-consistently balance heat production and transport in both rock and ice layers.

[30]
Title: The Pluto System After New Horizons
Journal-ref: Annual Reviews of Astronomy ans Astrophysics 2018
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The discovery of Pluto in 1930 presaged the discoveries of both the Kuiper Belt and ice dwarf planets, which are the third class of planets in our solar system. From the 1970s to the 19990s numerous fascinating attributes of the Pluto system were discovered, including multiple surface volatile species, Pluto's large satellite Charon, and its atmosphere. These attributes, and the 1990s discovery of the Kuiper Belt and Pluto's cohort of small Kuiper Belt planets, motivated the exploration of Pluto. That mission, called New Horizons (NH), revolutionized knowledge of Pluto and its system of satellites in 2015. Beyond providing rich geological, compositional, and atmospheric data sets, New Horizons demonstrated that Pluto itself has been surprisingly geologically active throughout the past 4 billion years, and that the planet exhibits a surprisingly complex range of atmospheric phenomenology and geologic expression that rival Mars in their richness.

[31]
Title: Interstellar communication. V. Introduction to photon information efficiency (in bits per photon)
Authors: Michael Hippke
Comments: 3 pages, 1 figure. Useful introduction for the previous parts of this series: arXiv:1706.03795, arXiv:1706.05570, arXiv:1711.05761, arXiv:1711.07962
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Quantum Physics (quant-ph)

How many bits of information can a single photon carry? Intuition says "one", but this is incorrect. With an alphabet based on the photon's time of arrival, energy, and polarization, several bits can be encoded. In this introduction to photon information efficiency, we explain how to calculate the maximum number of bits per photon depending on the number of encoding modes, noise, and losses.

[32]
Title: On the Optimal Choice of Nucleosynthetic Yields, IMF and Number of SN Ia for Chemical Evolution Modelling
Comments: 17 pages, 7 figures, submitted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

To fully harvest the rich library of stellar elemental abundance data, we require reliable models that facilitate our interpretation of them. Galactic chemical evolution (GCE) models are one example, and a key part is the selection of chemical yields from different nucleosynthetic enrichment channels, commonly asymptotic giant branch (AGB) stars, type Ia and core-collapse supernovae (SN Ia & CC-SN). We present a scoring system for yield tables based on their ability to reproduce proto-solar abundances within a simple parametrisation of the GCE modelling software Chempy. This marginalises over five galactic parameters, describing simple stellar populations (SSP) and interstellar medium (ISM) physics. Two statistical scoring methods, based on Bayesian evidence and leave-one-out cross-validation, are applied to four CC-SN tables; (a) for all mutually available elements and (b) for the 9 most abundant elements. We find that the yields of West & Heger (2017, in prep.) and Chieffi & Limongi (2004) (C04) are preferred for the two cases. For (b) the inferred best-fit parameters using C04 are $\alpha_\mathrm{IMF}=-2.45^{+0.15}_{-0.11}$ for the IMF high-mass slope and $\mathrm{N}_\mathrm{Ia}=1.29^{+0.45}_{-0.31}\times10^{-3}$ M$_\odot^{-1}$ for the SN Ia normalisation. These are broadly consistent across tested yield tables and elemental subsets, whilst not simply reproducing the priors. For (b) all yield tables consistently over- (under-)predict Si (Mg) which can be mitigated by lowering CC-SN explosion energies. Additionally, we show that Chempy can dramatically improve abundance predictions of hydrodynamical simulations by plugging tailored best-fit SSP parameters into a Milky Way analogue from Gutcke & Springel (2017). Our code, including a comprehensive tutorial, is freely available and can also provide SSP enrichment tables for any set of parameters and yield tables.

[33]
Title: The dynamics of the de Sitter resonance
Comments: Accepted for publication on Celestial Mechanics and Dynamical Astronomy
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We study the dynamics of the de Sitter resonance, namely the stable equilibrium configuration of the first three Galilean satellites. We clarify the relation between this family of configurations and the more general Laplace resonant states. In order to describe the dynamics around the de Sitter stable equilibrium, a one-degree of freedom Hamiltonian normal form is constructed and exploited to identify initial conditions leading to the two families.
The normal form Hamiltonian is used to check the accuracy in the location of the equilibrium positions. Besides, it gives a measure of how sensitive it is with respect to the different perturbations acting on the system. By looking at the phase-plane of the normal form, we can identify a \sl Laplace-like \rm configuration, which highlights many substantial aspects of the observed one.

[34]
Title: On the frequency dependence of p-mode frequency shifts induced by magnetic activity in Kepler solar-like stars
Comments: Accepted for publication in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The variations of the frequencies of the low-degree acoustic oscillations in the Sun induced by magnetic activity show a dependence with radial order. The frequency shifts are observed to increase towards higher-order modes to reach a maximum of about 0.8 muHz over the 11-yr solar cycle. A comparable frequency dependence is also measured in two other main-sequence solar-like stars, the F-star HD49933, and the young 1-Gyr-old solar analog KIC10644253, although with different amplitudes of the shifts of about 2 muHz and 0.5 muHz respectively. Our objective here is to extend this analysis to stars with different masses, metallicities, and evolutionary stages. From an initial set of 87 Kepler solar-like oscillating stars with already known individual p-mode frequencies, we identify five stars showing frequency shifts that can be considered reliable using selection criteria based on Monte Carlo simulations and on the photospheric magnetic activity proxy Sph. The frequency dependence of the frequency shifts of four of these stars could be measured for the l=0 and l=1 modes individually. Given the quality of the data, the results could indicate that a different physical source of perturbation than in the Sun is dominating in this sample of solar-like stars.

[35]
Title: Cosmology with the pairwise kinematic SZ effect: Calibration and validation using hydrodynamical simulations
Comments: 15 pages, 13 figures, 2 tables; submitted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

We study the potential of the kinematic SZ effect as a probe for cosmology, focusing on the pairwise method. The main challenge is disentangling the cosmologically interesting mean pairwise velocity from the cluster optical depth and the associated uncertainties on the baryonic physics in clusters. Furthermore, the pairwise kSZ signal might be affected by internal cluster motions or correlations between velocity and optical depth. We investigate these effects using the Magneticum cosmological hydrodynamical simulations, one of the largest simulations of this kind performed to date. We produce tSZ and kSZ maps with an area of $\simeq 1600~\mathrm{deg}^2$, and the corresponding cluster catalogues with $M_{500c} \gtrsim 3 \times 10^{13}~h^{-1}M_\odot$ and $z \lesssim 2$. From these data sets we calibrate a scaling relation between the average Compton-$y$ parameter and optical depth. We show that this relation can be used to recover an accurate estimate of the mean pairwise velocity from the kSZ effect, and that this effect can be used as an important probe of cosmology. We demonstrate that the residual systematic effects seen in our analysis are well below the remaining uncertainties on the sub-grid feedback models implemented in hydrodynamical simulations.

[36]
Title: Cosmic Neutrinos
Authors: Ofelia Pisanti
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

Neutrinos are key astronomical messengers, because they are undeflected by magnetic field and unattenuated by electromagnetic interaction. After the first detection of extraterrestrial neutrinos in the TeV-PeV region by Neutrino Telescopes we are entering a new epoch where neutrino astronomy becomes possible. In this paper I briefly review the main issues concerning cosmological neutrinos and their experimental observation.

[37]
Title: Observational Constraints on Oscillating Dark-Energy Parametrizations
Comments: 22 pages, 5 Tables, 18 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

We perform a detailed confrontation of various oscillating dark-energy parame-trizations with the latest sets of observational data. In particular, we use data from Joint Light Curve analysis (JLA) sample from Supernoave Type Ia, Baryon Acoustic Oscillations (BAO) distance measurements, Cosmic Microwave Background (CMB) observations, redshift space distortion, weak gravitational lensing, Hubble parameter measurements from cosmic chronometers, and the local Hubble constant value, and we impose constraints on four oscillating models. We find that all models are bent towards the phantom region, nevertheless in the three of them the quintessential regime is also allowed within 1$\sigma$ confidence-level. Furthermore, the deviations from $\Lambda$CDM cosmology are small, however for two of the models they could be visible at large scales, through the impact on the temperature anisotropy of the CMB spectra and on the matter power spectra.

[38]
Title: Spatial correlations of Si III detections in the local interstellar medium
Authors: M.K. Kuassivi
Comments: 3 pages, 2 figures, 1 table
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Since the developpment of astronephography, we know that the Sun is about to exit the Local Interstellar Cloud (LIC). To date, because of its rare absorption signatures and the paucity of suitable neighbour targets, the LIC interface has proved to be elusive to extensive investigations. Comparing the spatial distribution of Si III detections found in the litterature along with 3 new sigtlines, I show that most detections seem to arise from a cone whose axis is parallel to the LIC heliocentric velocity vector. I interpret this result as an evidence that the heliosphere is actually interacting with the LIC frontier.

[39]
Title: Optimization of Photospheric Electric Field Estimates for Accurate Retrieval of Total Magnetic Energy Injection
Journal-ref: Solar Phys., 292:191, 2017
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Estimates of the photospheric magnetic, electric and plasma velocity fields are essential for studying the dynamics of the solar atmosphere, for example through the derivative quantities of Poynting and relative helicity flux and by using of the fields to obtain the lower boundary condition for data-driven coronal simulations. In this paper we study the performance of a data processing and electric field inversion approach that requires only high-resolution and high-cadence line-of-sight or vector magnetograms -- which we obtain from Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory (SDO). The approach does not require any photospheric velocity estimates, and the lacking velocity information is compensated using ad hoc assumptions. We show that the free parameters of these assumptions can be optimized to reproduce the time evolution of the total magnetic energy injection through the photosphere in NOAA AR 11158, when compared to the recent estimates for this active region. However, we find that the relative magnetic helicity injection is reproduced poorly reaching at best a modest underestimation. We discuss also the effect of some of the data processing details on the results, including the masking of the noise-dominated pixels and the tracking method of the active region, both of which have not received much attention in the literature so far. In most cases the effect of these details is small, but when the optimization of the free parameters of the ad hoc assumptions is considered a consistent use of the noise mask is required. The results found in this paper imply that the data processing and electric field inversion approach that uses only the photospheric magnetic field information offers a flexible and straightforward way to obtain photospheric magnetic and electric field estimates suitable for practical applications such as coronal modeling studies.

[40]
Title: First detection of a virial shock with SZ data: implication for the mass accretion rate of Abell 2319
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Shocks produced by the accretion of infalling gas in the outskirt of galaxy clusters are expected in the hierarchical structure formation scenario, as found in cosmological hydrodynamical simulations. Here, we report the detection of a shock front at a large radius in the pressure profile of the galaxy cluster A2319 at a significance of $8.6\sigma$, using Planck thermal Sunyaev-Zel'dovich data. The shock is located at $(2.93 \pm 0.05) \times R_{500}$ and is not dominated by any preferential radial direction. Using a parametric model of the pressure profile, we derive a lower limit on the Mach number of the infalling gas, $\mathcal{M} > 3.25$ at 95\% confidence level. These results are consistent with expectations derived from hydrodynamical simulations. Finally, we use the shock location to constrain the accretion rate of A2319 to $\dot{M} \simeq (1.4 \pm 0.4) \times 10^{14}$ M$_\odot$ Gyr$^{-1}$, for a total mass, $M_{200} \simeq 10^{15}$ M$_\odot$.

[41]
Title: The Abacus Cosmos: A Suite of Cosmological N-body Simulations
Comments: 11 pages, 5 figures, 3 tables. ApJS submitted
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We present a public data release of halo catalogs from a suite of 125 cosmological $N$-body simulations from the Abacus project. The simulations span 40 $w$CDM cosmologies centered on the Planck 2015 cosmology at two mass resolutions, $4\times 10^{10}\;h^{-1}M_\odot$ and $1\times 10^{10}\;h^{-1}M_\odot$, in $1.1\;h^{-1}\mathrm{Gpc}$ and $720\;h^{-1}\mathrm{Mpc}$ boxes, respectively. The boxes are phase-matched to suppress sample variance and isolate cosmology dependence. Additional volume is available via 16 boxes of fixed cosmology and varied phase; a few boxes of single-parameter excursions from Planck 2015 are also provided. Catalogs spanning $z=1.5$ to $0.1$ are available for friends-of-friends and Rockstar halo finders and include particle subsamples. All data products are available at https://lgarrison.github.io/AbacusCosmos

[42]
Title: Sunspot number second differences as a precursor of the following 11-year sunspot cycle
Comments: 16 pages, 10 figures, published in ApJ
Journal-ref: ApJ. 850 (2017) 81
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Forecasting the strength of the sunspot cycle is highly important for many space weather applications. Our previous studies have shown the importance of sunspot number variability in the declining phase of the current 11-year sunspot cycle to predict the strength of the next cycle when the minimum of the current cycle has been observed. In this study we continue this approach and show that we can remove the limitation of having to know the minimum epoch of the current cycle, and that we can already provide a forecast of the following cycle strength in the early stage of the declining phase of the current cycle. We introduce a method to reliably calculate sunspot number second differences (SNSD) in order to quantify the short-term variations of sunspot activity. We demonstrate a steady relationship between the SNSD dynamics in the early stage of the declining phase of a given cycle and the strength of the following sunspot cycle. This finding may bear physical implications on the underlying dynamo at work. From this relation, a relevant indicator is constructed that distinguishes whether the next cycle will be stronger or weaker compared to the current one. We demonstrate that within 24-31 months after reaching the maximum of the cycle, it can be decided with high probability (0.96) whether the next cycle will be weaker or stronger. We predict that sunspot cycle 25 will be weaker than the current cycle 24.

[43]
Title: Testing the Detection Significance on the Large Scale Structure by a JWST Deep Field Survey
Comments: 10 pages, 9 figures, submitted to ApJ
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

In preparation for deep extragalactic imaging with the James Webb Space Telescope, we explore the clustering of massive halos at $z=8$ and $10$ using a large N-body simulation. We find that halos with masses $10^9$ to $10^{11}$ $h^{-1}\;M_\odot$, which are those expected to host galaxies detectable with JWST, are highly clustered with bias factors ranging from 5 and 30 depending strongly on mass, as well as on redshift and scale. This results in correlation lengths of 5--10$h^{-1}\;{\rm Mpc}$, similar to that of today's galaxies. Our results are based on a simulation of 130 billion particles in a box of $250h^{-1}\;{\rm Mpc}$ size using our new high-accuracy ABACUS simulation code, the corrections to cosmological initial conditions of (Garrison et al. 2016, 2016MNRAS.461.4125G), and the Planck 2015 cosmology. We use variations between sub-volumes to estimate the detectability of the clustering. Because of the very strong inter-halo clustering, we find that surveys of order 25$h^{-1}\;{\rm Mpc}$ comoving transverse size may be able to detect the clustering of $z=8$--$10$ galaxies with only 500-1000 survey objects if the galaxies indeed occupy the most massive dark matter halos.