Day 1343

Monday.  Tuesday.  Wednesday.

1711.09882
The shape of galaxy dark matter haloes in massive galaxy clusters: insights from strong gravitational lensing
Jauzac, Harvey, Massey

Assess how much unused strong lensing information is available in the deep HST imaging and VLT/MUSE spectroscopy of the Frontier Field clusters.  As a pilot study, analyze galaxy cluster MACS J0416.1-2403 (z=0.397, M(R<200 kpc)=1.6e14 Msun), which has 141 multiple images with spectroscopic redshifts.  Find that many additional parameters in a cluster mass model can be constrained, and that adding even small amounts of extra freedom to a model can dramatically improve its figures of merit.  Use this information to constrain the distribution of DM around cluster member galaxies, simultaneously with the cluster's large-scale mass distribution.  Find tentative evidence that some galaxies' dark matter has surprisingly similar ellipticity to their stars (unlike in the field, where it is more spherical), but that its orientation is often misaligned.  When non-coincident DM and baryonic haloes are allowed, the model improves by 35%.  This technique may provide a new way to investigate the processes and timescales on which DM is stripped from galaxies as they fall into a massive cluster.  The preliminary conclusions will be made more robust by analyzing the remaining 5 Frontier Field clusters.


1711.10017
The effect of baryons in the cosmological lensing PDFs
Castro, et al

Understanding the effect of baryonic matter on the LSS is one of the challenges to be faced in cosmology.  In this work, thoroughly study the effect of baryonic physics on different lensing statistics.  Making use of the Magnetic Pathfinder suite of sims, show that on angular resolutions already achieved ongoing surveys the influence of luminous matter on the 1pt lensing statistics of point sources is significant, enhancing the probability of magnified objects with mu>3 by a factor of 2 and the occurrence of multiple-images by a factor of 6-30 depending on the source redshift.  Also discuss the dependence of the lensing statistics on the angular resolution of surveys.  The results and methodology were carefully tested in order to guarantee that the uncertainties are much smaller than the effects here presented.


1711.10018
Deriving galaxy cluster velocity anisotropy profiles from a joint analysis of dynamical and weak lensing data
Stark, Miller, Halenka

Present an analytic approach to lift the mass-anisotropy degeneracy in clusters of galaxies by utilizing the line-of-sight velocity dispersion of clustered galaxies jointly with WL-inferred masses.  More specifically, solve the spherical Jeans equation by assuming a simple relation between the line-of-sight velocity dispersion and the radial velocity dispersion and recast the Jeans equation as a Bernoulli differential equation which has a well-known analytic solution.  First test the method in cosmological N-body simulations and then derive the anisotropy profiles for 35 archival data galaxy with an average redshift of <z_c>=0.25.  The resulting profiles yield a weighted average global value of <beta(0.2<=r/r200<=1)>=0.35±0.28(stat)±0.15(sys).  This indicates that clustered galaxies tend to globally fall on radially anisotropic orbits.  Note that this is the first attempt to derive velocity anisotropy profiles for a cluster sample of this size utilizing joint dynamical and WL data.

Day 1342

Thursday.

1711.07985
Declining rotation curves at $z=2$: a natural phenomenon in $\Lambda$CDM cosmology
Teklu, et al

Selecting disk galaxies from the cosmological, hydrodynamical sim Magneticum Pathfinder, show that almost half of the poster child disk galaxies at z=2 show significantly declining rotation curves and low DM fractions, very similar to recently reported observations.  These galaxies do not show any anomalous behavior, reside in standard DM haloes and typically grow significantly in mass until z=0, where they span all morphological classes, including disk galaxies matching present day rotation curves and observed DM fractions.  The findings demonstrate that declining rotation curves and low DM fractions in rotation dominated galaxies at z=2 appear naturally within the LCDM paradigm and reflect the complex baryonic physics, which plays a role at the peak epoch of SF.  In addition, find that dispersion dominated galaxies at z=2, which host a significant gas disk, exhibit similar shaped rotation curves as the disk galaxy population, rendering it difficult to differentiate between these two populations with currently available observation techniques.

Day 1341

Tuesday.  Wednesday.

1711.06692
Influence of XUV Irradiation from Sgr A* on planetary habitability and occurrence of panspermia near the Galactic center
Chen, Forbes, Loeb

Find that, out to ~20 pc from Sgr A*, the XUV flux emitted during its quasar phase can remove several percent of a planet's H/He envelope by mass; in many cases, this removal results in bare rocky cores, many of which situated in the habitable zones (HZs) of G-type stars.  The erosion of sub-neptune sized planets may be one of the most prevalent channels by which terrestrial super-Earths are created near the GalacticCenter.  As such, the planet population demographics may be quite different close to Sgr A* than in the Galaxy's outskirts.  The high stellar densities in this region (about seven orders of magnitude greater than the solar neighborhood) imply that the distance between neighboring rocky worlds is short (500-5000AU).  The proximity between potentially habitable terrestrial planets may enable the onset of widespread interstellar panspermia near the nuclei of galaxies.  More generally, predict these phenomena to be ubiquitous for planets in nuclear star clusters (NSCs) and ultra-compact dwarfs (UCDs).


1711.06801
Whole planet coupling between climate, mantle, and core: implications for the evolution of rocky planets
Foley, Driscoll

Earth's climate, mantle, and core interact over geologic timescales.  Climate influences whether plate tectonics can take place on a planet, with cool climates being favorable for plate tectonics because they enhance stresses in the lithosphere, suppress plate boundary annealing, and promote hydration and weakening of the lithosphere.  Plate tectonics plays a vital role in the long-term carbon cycle, which helps to maintain a temperate climate.  Plate tectonics provides long-term cooling of the core, which is vital for generating a magnetic field, and the magnetic field is capable of shielding atmospheric volatiles from the solar wind.  Coupling between climate, mantle, and core can potentially explain the divergent evolution of Earth and Venus.  As Venus lies too close to the sun for liquid water to exist, there is no long-term carbon cycle and thus an extremely hot climate.  Therefore plate tectonics cannot operate and a long-lived core dynamo cannot be sustained due to insufficient core cooling.  On planets within the habitable zone where liquid water is possible, a wide range of evolutionary scenarios can take place depending on initial atmospheric composition, bulk volatile content, or the timing of when plate tectonics initiates, among other factors.  Many of these evolutionary trajectories would render the planet uninhabitable.  However, there is still significant uncertainty over the nature of the coupling between climate, mantle, and core.  Future work is needed to constrain potential evolutionary scenarios and the likelihood of an Earth-like evolution.


1711.06863
Chasing the peak: optimal statistics for weak shear analysis
Smit, Kuijken

WL analyses are fundamentally limited by the intrinsic, non-Gaussian distribution of galaxy shapes.  Explore alternate statistics for samples of ellipticity measurements that are unbiased, efficient, and robust.  Take the non-linear mapping of gravitational shear and the effect of noise into account.  Then discuss how the distribution of individual galaxy shapes in the observed field of view can be modeled by fitting Fourier modes to the shear pattern directly.  Simulate samples of galaxy ellipticities, using both theoretical distributions and real data for ellipticities and noise; determine the possible bias Delta e, the efficiency eta and the robustness of the least absolute deviations, the biweight, and the convex hull peeling estimators, compared to the canonical weighted mean.  Using these statistics for regression, show the applicability of direct Fourier mode fitting.  These estimators can be unbiased in the absence of noise, and decrease noise bias by more than ~30%.  The convex hull peeling estimator distribution is centered around the underlying shear, and its bias least affected by noise.  The least absolute deviations estimator is found to be the most efficient estimator in almost all cases, except in the Gaussian case, where it's still competitive (0.83<eta<5.1) and therefore robust.  These results hold when fitting Fourier modes, where amplitudes of variation in ellipticity are determined to the order of 1e-3.  The peak of the ellipticity distribution is a direct tracer of the underlying shear and unaffected by noise; show that estimators that are sensitive to a central cusp perform more efficiently, potentially reducing uncertainties by more than 50% and significantly decreasing noise bias.


1711.07297
Models of gravitational lens candidates from Space Warps CFHTLS
Küng, Saha, et al

Report modeling follow-up of recently-discovered gravitational-lens candidates in CFHTLS.  Lens modeling was done by a small group of specially-interested volunteers from the SpaceWarps citizen-science community who originally found the candidate lenses.  Models are categorized according to 7 diagnostics indicating (a) the image morphology and how clear or indistinct it is, (b) whether the mass map and synthetic lensed image appear to be plausible, and (c) how the lens-model mass compares with the stellar mass and the abundance-matched halo mass.  The lensing masses range from ~1e11 Msun to >1e13 Msun.  Preliminary estimates of the stellar masses show a smaller spread in stellar mass (except for two lenses): a factor of a few below or above ~1e11 Msun.  Therefore, expect the stellar-to-total mass fraction to decline sharply as lensing mass increases.  The most massive system with a convincing model is J1434+522 (SW05).  The two low-mass outliers are J0206-095 (SW19) and J2217+015 (SW42); if these two are indeed lenses, they probe an interesting regime of very low SF efficiency.  Some improvements to the modeling software (SpaghettiLens), and discussion of strategies regarding scaling to future surveys with more and frequent discoveries, are included.


1711.07467
Complete super-sample lensing covariance n the response approach
Barreira, Krause, Schmidt

Derive the complete SSC of the matter and WL convergence power spectra using the PS response formalism to accurately describe the coupling of super-to-intra survey modes.  The SSC term is completely characterized by the survey window function, the NL matter PS and the full first-order NL power spectrum response function, which describes the response to SS density and tidal field perturbations.  Separate universe simulations can efficiently measure these responses in the NL regime of structure formation, which is necessary for lensing applications.  Under the Limber and flat-sky approximations, show that the tidal contributions, which have not been included in cosmological analyses so far, represent a significant fraction (~20-25%) of the total SSC, even for an isotropic survey footprint on the sky.  The SSC is the dominant off-diagonal contribution to the total lensing covariance for survey sky fractions f_sky <~0.3, making it important to include these tidal terms in cosmic shear analyses.


1711.07919
A quadruply lensed SN Ia: gaining a time-delay...losing a standard candle
Yahalomi, Schechter, Wambsganss

Investigate the flux ratio anomalies between macro-model predictions and the observed rightness of the SN iPDF16geu, as published in a recent paper by More+ 2017.  This group suggested that these discrepancies are, qualitatively, likely due to microlensing.  Analyze the plausibility of attributing this discrepancy to microlensing, and find that the discrepancy is too large to be due to microlensing alone.  This is true whether one assumes knowledge of the luminosity of the SN or allows the luminosity to be a free parameter.  Varying the dark/stellar ratio likewise doesn't help.  In addition, other macro-models with quadruplicity from external shear or ellipticity do not significantly improve to model.  Finally, microlensing also makes it difficult to accurately determine the standard candle brightness of the SN, as the likelihood plot for the intrinsic magnitude of the source (for a perfect macro-model) has a FWHM of 0.73 magnitudes.  As such, the error for the standard candle brightness is quite large.  This reduces the utility of the standard candle nature of type Ia SN.

Day 1340

Monday.

1711.06267
There is no missing satellites problem
Kim, Peter, Hargis

A critical challenge to the CDM paradigm is that there are fewer satellites observed around the MW than found in simulations of DM substructure.  Show that there is a match between the observed satellite counts corrected by the detection efficiency of the SDSS (for luminosities L<~340 L_sun) and the number of luminous satellites predicted by CDM, assuming an empirical relation between stellar mass and halo mass.  The "missing satellites problem", cast in terms of number counts is thus solved, and imply that luminous satellites inhabit sub halos as smalls 1e7-8 Msun.  The total number of MW satellites depends sensitively on the spatial distribution of satellites.  Also show that WDM models with a thermal relic mass smaller than 4 keV are robustly ruled out, and that limits of m_WDM <~ 8keV from the MW are probable in the near future.  Similarly stringent constraints can be placed on any DM model that leads to a suppression of the matter power spectrum on ~1e7 Msun scales.  Measurements of completely dark halos below 1e8 Msun, achievable with substructure lensing, are the next frontier for tests of CDM.


1711.06273
Exploring the brighter fatter effect with the hyper suprime-cam
Coulton, Armstrong, Smith, Lupton, Spergel

The brighter fatter effect has been postulated to arise due to the build up of a transverse electric field, produced as photo-charges accumulate in the pixels' potential wells.  Investigate the brighter fatter effect in HSC by examine flat fields and moments of stars.  Observe deviations from the expected linear relation in the photon transfer curve, luminosity dependent correlations between pixels in flat field images and a luminosity dependent PSF in stellar observations.  Under the key assumptions of translation invariance and Maxwell's equations in thequasi-static limit, give a first-principles proof that the effect can be parameterized by a translationally invariant scalar kernel.  Describe how this kernel can be estimated from flat fields and discuss how this kernel has been used to remove the brighter fatter distortions in HSC images.  Find that the correction restores the expected linear relation in the photon transfer curves and significantly reduces, but does not completely remove, the luminosity dependence of the PSF over a wide range of magnitudes.

Day 1339

Friday.

1711.05761
Interstellar communication. III. Optimal frequency to maximize data rate
Hippke, Forgan

The optimal frequency for interstellar communication, using "Earth 2017" technology, was derived in papers I and II of this series.  The framework included models for the loss of photons from diffraction (free space), interstellar extinction, and atmospheric transmission.  A major limit of current technology is the focusing of wavelengths lambda < 300 nm (UV).  When this technological constraint is dropped, a physical bound is found at lambda ~ 1 nm (E~keV) for distances out to kpc.  While shorter wavelengths may produce tighter beams and thus higher data rates, the physical limit comes from surface roughness of focusing devices at the atomic level.  This limit can be surpassed by beam-forming with EM fields, e.g. using a free electron laser, but such methods are not energetically competitive.  Current lasers are not yet cost efficient at nm wavelengths, with a gap of two orders of magnitude, but future technological progress may converge on the physical optimum.  Recommend expanding SETI efforts towards targeted (at us) monochromatic (or narrow band) X-ray emission at 0.5-2 keV energies.


1711.06029
Measuring the hydrostatic mass bias in galaxy clusters by combining Sunyaev-Zel'dovich and CMB lensing data
Hurier, Angulo

The cosmological parameters preferred by the CMB primary anisotropies predict many more galaxy clusters than those that have been detected via the tSZ effect.  This tension has attracted considerable attention since it could be evidence of physics beyond the simplest LCDM model.  However, an accurate and robust calibration of the mass-observable relation for clusters is necessary for the comparison, which has been proven difficult to obtain so far.  Here, present new constraints on the mass-pressure relation by combining tSZ and CMB lensing measurements about optically-selected clusters.  Consequently, the galaxy cluster sample is independent from the data employed to derive cosmological constraints.  Estimate an average hydrostatic mass bias of b=0.26±0.07, with no significant mass nor z evolution.  This value greatly reduces the tension between the predictions of LCDM and the observed abundance of tSZ clusters while being in agreement with recent estimations from tSZ clustering.  On the other hand, the value for b is higher than the predictions from hydro-dynamical simulations.  This suggests the existence of mechanisms driving large departures from hydrostatic equilibrium and that are not included in state-of-the-art simulations, and/or unaccounted systematic errors such as biases in the cluster catalogue due to the optical selection.

Day 1338

Monday.  Tuesday, network issues at Cornell (arXiv).  Wednesday.  Thursday.

1711.05272
The stellar populations of two ultra-diffuse galaxies from optical and near-infrared photometry
Pandya, et al

Present observational constraints on the stellar populations of 2 UDGs using optical through NIR data, from Spitzer IRAC 3.6um and 4.5um imaging, archival optical imaging, and with a Bayesian SED fitting framework.  3 samples : 1 field UDG, 1 cluster UDG, and one cluster dwarf elliptical.  All 3 galaxies have NIR colors that are significantly different form each other.  The Virgo UDG is old (~7.7 Gyr) and significantly metal poor (Z/Zsun <~ -1.0).  The field UDG is probably younger than the Virgo UDG, with an extended SFH and an age posterior extending down to ~3 Gyr.  The stellar metallicity of the field UDG is sub-solar, but higher than that of the Virgo UDG, with Z/Zsun=-0.63+0.35-0.62; in the case of exactly zero diffuse interstellar dust, the field UDG may even have solar metallicity.  The spectroscopically confirmed globular clusters of the Virgo UDG have similar optical-NIR colors as the UDG itself, with empirical color relations suggesting sub-solar metallicities and supporting the metal-poor nature of it.  With it and several Coma UDGs, a general picture is emerging where cluster UDGs may be "failed" galaxies, but the field UDG seems more consistent with a stellar feedback-induced expansion scenario.


1711.05276
Disruption of dark matter substructure: fact or fiction?
van den Bosch, Ogiya, Hahn, Burkert

Use both analytical estimates and idealized numerical simulations to investigate whether the DM substructure disruption in N-body sims is mainly physical (tidal heating and stripping) or numerical (i.e., artificial).  Show that, contrary to naive expectation, sub haloes that experience a tidal shock Delta E that exceeds the smbhalo's binding energy, E_b, do not undergo disruption, even when Delta E/E_b is as large as 100.  Along the same line, and contrary to existing claims in the literature, instantaneously stripping matter from the outskirts of a DM subhalo also does not result in its complete disruption, even when the instantaneous remnant has positive binding energy.  In addition, show that today heating due to high-speed (impulsive) encounters with other sub haloes ('harassment'), is negligible compared to the tidal effects due to the host halo.  Hence conclude that in the absence of baryonic processes, the complete, physical disruption of CDM substructure is extremely rare, and that most disruption in numerical simulations therefore must be artificial.  Discuss various processes that have been associated with numerical over merging, and conclude that inadequate force-softening is the most likely culprit.

Day 1337

Friday.

1711.03234
SDSS-V: Pioneering Panoptic spectroscopy
Kollmeier, et al

SDSS-V will be an all-sky, multi-epoch spectroscopic survey of over 6M objects.  It is designed to decode the history of the Milky Way, trace the emergence of the chemical elements, reveal the inner workings of stars, and investigate the origin of planets.  It will also create an integral-field spectroscopic map of the gas in the Galaxy and the Local Group that is 1000x larger than the current state of the art and at high enough spatial resolution to reveal the self-regulation mechanisms of galactic ecosystems.  SDSS-V will pioneer systematic, spectroscopic monitoring across the whole sky, revealing changes on timescales from 20 minutes to 20 years.  The survey will thus track the flickers, flares, and radical transformations of the most luminous persistent objets in the universe: massive black holes growing at the centers of galaxies.  The scope and flexibility of SDSS-V will be unique among extant and future spectroscopic surveys: it is all-sky, with matched survey infrastructures in both hemispheres; it provides near-IR and optical multi-object fiber spectroscopy that is rapidly reconfigurable to serve high target densities, targets of opportunity, and time-domain monitoring; and it provides optical, ultra-wide-field integral field spectroscopy.  SDSS-V, with its programs anticipated to start in 2020, will be well-timed to multiply the scientific output from major space missions (e.g., TESS, Gaia, eROSITA) and ground-based projects.  SDSS-V builds on the 25-year heritage of SDSS's advances in data analysis, collaboration infrastructure, and product deliverables.  The project is now refining its science scope, optimizing the survey strategies, and developing new hardware that builds on the SDSS-IV infrastructure.  Present here an overview of the current state of these developments as the worldwide consortium of institutional and individual members are sought to be built.

Day 1336

Thursday.

1711.02677
Scale dependence of galaxy biasing investigated by weak gravitational lensing: an assessment using semi-analytic galaxies and simulated lensing data
Simon, Hilbert

Galaxies are biased tracers of the matter density on cosmological scales.  For future tests of galaxy models, refine and assess a method to measure galaxy biasing as function of physical scale k with WL.  This method enables reconstruction of the galaxy bias factor b(k) as well as the galaxy-matter correlation r(k) on physical scales between 0.01 h/Mpc <~ k <~ 10 h/Mpc for redshift-binned lens galaxies below z <~0.6.  In the refinement, account for an intrinsic alignment of source ellipticities, and correct for the lensing magnification of the angular number density of the lens galaxies to improve the accuracy of the reconstructed r(k).  For simulated data, the reconstructions achieve an accuracy of 3-7% (68% CL) over the above k-range for a survey area and a typical depth of contemporary ground-based surveys.  Realistically the accuracy is, however, probably reduced to about 10-15%, mainly by systematic errors in the assumed intrinsic source alignments, the fiducial cosmology, and the z distributions of lens and source galaxies (in that order).  Furthermore, the reconstruction technique employs physical templates for b(k) and r(k) that elucidate the impact of central galaxies and the halo-occupation statistics of satellite galaxies on the scale-dependence of galaxy bias, which is discussed in the paper.  In a first demonstration, apply this method to previous measurements in the Garching-Bonn-Deep Survey and give a physical interpretation of the lens population.


1711.02780
Mining the Kilo-Degree Survey for solar system objects
Mahlke, et al

The search for minor bodies in the solar system promises insights into its formation history.  Wide imaging surveys offer the opportunity to serendipitously discover and identify these traces of planetary formation and evolution.  Aim to present a method to acquire position, photometry, and proper motion measurements of solar system objects in surveys using dithered image sequences.  The application of this method on KiDS is demonstrated.  Optical images of 346 sq deg fields of the sky are searched in up to 4 filters using the AstrOmatic software suite to reduce the pixel to catalog data.  The solar system objects within the acquired sources are selected based on a set of criteria depending on their number of observation, motion, and size.  The Virtual Observatory SkyBoT tool is used to identify known objects.  Observed 20,221 SSO candidates, with an estimate false-positive content of less than 0.05%.  Of these SSO candidates, 53.4% are identified by  SkyBoT.  KiDS can detect previously unknown SSOs because of its depth and coverage at high ecliptic altitude, including parts of the Souther Hemisphere.  Thus, expect the large fraction of the 46.6% of unidentified objects to be truly new SSOs.  The method is applicable to a variety of dithered surveys such as DES, LSST, and Euclid.  It offers a quick and easy-to-implement search for solar system objects.  SkyBoT can then be used to estimate the completeness of the recovered sample.

Day 1335

Wednesday.

1711.02090
Very low-luminosity galaxies in the early universe have observed sizes similar to single star cluster complexes
Bouwens, van Dokkum, et al

Compare the sizes and luminosities of 307 faint z=6-8 sources revealed by HFF with sources in the nearby universe.  Making use of the latest lensing models and data from the first four HFF clusters with an extensive suite of public lens models, measure both the sizes and luminosities for 153 z~6, 101 z~7, and 53 z~8 galaxies.  The sizes range over more than a decade from ~500 to <50 pc.  Extremely small sizes are inferred for many of the lowest luminosity sources, reaching individual sizes as small as 10-30 pc (the smallest is 11-6+28 pc).  The uncertainty in these measures ranges from 80 pc for the largest sources to typically about 20 pc for the smallest.  Such sizes are smaller than extrapolations of the size-luminosity relation, and expectations for the completeness of the faint samples, suggesting a likely break in the size-luminosity relation at ~-17 mag with size proportional to L^(0.5-0.11+0.10).  The sizes and luminosities of the lowest-luinosity sources are similar to those of single star cluster complexes like 30 Doradus in the lower-z universe and -- in a few cases -- super star clusters.  Remarkably, the identification of these compact, faint star-forming sources in the z~6-8 universe also allow to set upper limits on the porto-globular cluster LF at z~6.  Comparisons with recent models allows ruling out (with some caveats) some scenarios for porto-globular cluster formation and set useful upper limits on other less extreme ones.  The results suggest that discovering a bone-fide population of forming globular clusters at high-z is very close.

Day 1334

Tuesday.  A few asteroid A/2017 U1 papers came out today.

1711.01342
Solar system science with ESA Euclid
Carry

With current survey design, about 150k SSOs (solar system objects), mainly from the astroid main belt, should be observed by Euclid.  These obeys will all have high inclination.  There is a potential for discovery of several 10k SSOs, in particular KBOs at high declination.  Euclid observations will refine the spectral classification of SSOs by extending the spectral coverage provided by, e.g. Gaia and the LSST to 2 microns.  The time-resolved photometry, combined with sparse photometry will contribute to the determination of SSO rotation period, spin orientation, and shape model.  The sharp and stable point-spread function of Euclid will also allow to resolve KBO binary systems and detect activity around Centaurs.  The depth of Euclid survey, its spectral coverage, and observation cadence has great potential for Solar System research.  A dedicated processing for SSOs is being set in place to produce catalogs of astrometry, multicolor and time-resolved photometry, and spectral classification of some 1e5 SSOs, delivered as Legacy Science.

Day 1333

Monday.

1711.00856
Does the existence of a plane of satellites constrain properties of the Milky Way?
Pawlowski

Find no evidence for strong correlations that would allow conclusions the host halo properties from the mere existence of the VPOS (the Vast Polar Structure) around our Galaxy.  Looked at correlations between properties of satellite galaxy planes fitted to cosmo sims in the ELVIS suite and properties of their host DM haloes.


1711.00860
Hunting faint dwarf galaxies in the field using integrated light surveys
Danieli, van Dokkum, Conroy

Discuss an alternative approach for future systematic searches of low mass dwarf galaxies, <~1e6 Msun.  By exploring the limiting surface brightness-spatial resolution (mu_eff,lim - theta) parameter space, suggest that dwarfs in the Local Volume, between 3 and 10 Mpc, are expected to be detected very effectively and in large numbers using integrated light photometric surveys, complementary to the classical star counts method.  Use a sample of dwarf galaxies in the Local Group to construct relations between their photometric and strutctural parameters, M* - mu_eff,V and M* - R_eff.  Use these relations, along with assumed functional forms for the halo mass function and the stellar mass - halo mass relation, to calculate the lowest detectable stellar masses in the Local Volume and the expected number of galaxies as a function of the limiting surface brightness and spatial resolution.  The number of detected galaxies depends mostly on the limiting surface brightness for distances >3 Mpc while spatial resolution starts to play a role for galaxies at distances >8 Mpc.  Surveys with mu_eff,lim ~ 30 mag/arcsec^2 should be able to detect galaxies with stellar masses down to ~1e4 M* [Msun?] in the Local Volume.  Depending on the form of the SMHM relation, the expected number of dwarf galaxies with distances between 3 and 10 Mpc is 0.04-0.35 per square degree, assuming a limiting surface brightness of ~29-30 mag/arcsec^2 and a spatial resolution < 4".  Plan to search for a population of low mass dwarfs by performing a blank photometric survey with the Dragonfly Telephoto Array, an imaging system optimized for the detection of extended ultra-low surface brightness structures.


1711.01184
Quasi-stellar objects acting as strong gravitational lenses in the SDSS-III BOSS survey
Meyer, Delubac, Kneib, Courbin

Present a sample of 12 QSOs potentially acting as SL on BG emission line galaxies (ELGs) or Lyman-alpha emitters (LAEs).  The candidates are selected through a systematic search of the 350793 QSOs spectra in the SDSS-III DR12 within BOSS.  Candidates are identified by looking for compound spectra, where additional emission lines cannot be associated with the spectral features of the QSOs.  The narrow diameter of BOSS fibers (2") ensures that the object responsible for the additional emission lines must lie close to the LoS of the QSO.  Focus the search on additional objects securely identified at higher redshifts than the QSOs.  Among the 12 candidates identified, 9 have definite evidence for the presence of BG ELG identified by at least 4 higher-z emission lines.  The remaining 3 probable candidates present a strong asymmetrical emission line attributed to a higher-redshift LAE.  The QSO-Galaxy lens candidates have QSO redshifts in the range 0.24 < z_QSO < 0.66 and background galaxy redshifts in the range 0.48 <~ z_s <~ 0.94 whereas the QSO-LAE lens candidates have 0.75 < z_QSO < 1.23 and source LAE z in the range 2.17 < z_s < 4.48.  Upon confirmation of the lensing nature of the systems, this sample may quadruple the number of known QSOs acting as SLs.  Further imaging of the full sample will allow to model the radial mass profile of QSO host galaxies and study the scaling relations between SMBHs and their host galaxies.

Day 1332

Friday.

1711.00481
The impact of environment on the stellar mass - halo mass relation
Golden-Marx, Miller

A large variance exists in the amplitude of the stellar mass - halo mass (SMHM) relation for group and cluster-size halos.  Show that the magnitude gap between the BCG and its second or 4th brightest neighbor accounts for a significant portion of this variance.  Find that at fixed halo mass, galaxy clusters with a higher magnitude gap have a higher BCG stellar mass.  This relationship is also observed in semi-analytic representations of low-z galaxy clusters in simulations.  This SMHM-magnitude gap stratification likely results from BCG growth via hierarchical mergers and may link assembly of the halo with the growth of the BCG.  Using a Bayesian model, quantify the importance of the magnitude gap in the SMHM relation results in a large reduction in the inferred intrinsic scatter in the BCG stellar mass at fixed halo mass.  Discuss the ramifications of this result in the context of galaxy formation models of centrals in group and cluster-sized halos.

Day 1331

Thursday.

1711.00403
Dark Energy Survey Year 1 results: a precise H0 measurement from DES Y1, BAO, and D/H data
DES collaboration, et al

Combine DES Y1 clustering and WL data with BAO and BBN experiments to constrain the Hubble constant.  Assuming a flat LCDM model with minimal neutrino mass (sum m_nu = 0.06 eV) find H0=67.2+1.2-1.0 km/s/Mpc (68% CL).  This result is completely independent of Hubble constant measurements based on the distance ladder, CMB anisotropies (both temperature and polarization), and strong lensing constraints.  There are now 5 data sets that: a) have no shared observational systematics; and b) each constrain the Hubble constant with a few % level precision.  Compare these 5 independent measurements, and find that, as a set, the difference between them are significant at the 2.1 sigma level (chi^2/dof=20.1/11, probability to exceed=4%).  This difference is low enough that the data sets are considered statistically consistent with each other.  The best fit Hubble constant obtained by combining all 5 data sets is H0=69.1+0.4-0.6 km/s/Mpc.

Day 1330

Wednesday.

1710.11129
A one percent determination of the primordial deuterium abundance
Cooke, Pettini, Steidel

A reanalsys of a near-pristine absorption system at z_abs=2.52564 towards the quasar Q1243+307, based on observations on HIRES eschell spectrograph at Keck.  The absorption system has oxygen abundance [O/H]=-2.769±0.028, which is among the lowest metallicity systems currently known where a precise measurement of the D abundance is afforded.  Based on eight D I absorption lines, the D abundance of this gas cloud is log10(D/H)=-4.622±0.015, which is in very good agreement with the results previously reported by Kirkman+2003, but with an improvement on the precision of this single measurement by a factor of ~3.5.  Combining this new estimate with the previous sample of 6 high precision and homogeneously analyzed D/H measurements, deduce that the primordial deuterium abundance is log10(D/H)_P=-4.5974±0.0052 or (D/H)_P=(2.527±0.030)e-5; this value corresponds to a one percent determination of the primordial D abundance.  Combining the result with a BBN calculation that uses the latest nuclear physics input, find that the baryon density derived from BBN agrees to within 2 sigma of the latest results from the Planck CMB data.


1710.11131
The dearth of z~10 galaxies in all HST legacy fields -- the rapid evolution of the galaxy population in the first 500 Myr
Oesch, et al

HST legacy fields spanning >800 arcmin^2 in search of z~10 galaxy candidates and the study of their UV luminosity function (LF).  New z~10 candidates selected from the full HFF (Hubble Frontier Field) data set.  Despite the addition, find low abundance of z~10 candidates with only 9 reliable sources identified in all prime HST datasets that include HUDF09/12, HUDF/XDF, al the CANDELS fields, and HFF.  Based on this comprehensive search, find that the UV LF decreases by one order of magnitude from z~8 to z~10 at all luminosities over a 4 magnitude range.  This also implies that this accelerated evolution compared to lower z can entirely be explained by the fast build-up of the DM halo mass function at z>8.  Consequently, the predicted UV LFs from several models of galaxy formation are in good agreement with this observed trend, even though the measured UV LF lies at the low end of model predictions.  In particular, the number of only 9 observed candidate galaxies is lower, by ~50%, than predicted by galaxy evolution models.  The difference is generally still consistent within the Poisson and cosmic variance uncertainties.  However, essentially all models predict larger numbers than observed.   Discuss the implications of these results in light of the upcoming JWST mission, which is poised to find much larger samples of z~10 galaxies as we as their progenitors at less than 400 Mir after the Big Bang.


1710.11134
Is life most likely around sun-like stars?
Lingam, Loeb

Consider the habiltability of Earth-analogs around stars of different masses, which is regulated by the stellar lifetime, stellar wind-induced atmospheric erosion, and biologically active UV irradiance.  By estimating the timescales associated with each of these items, show that they collectively impose limits on the habitability of Earth-analogs.  Conclude that planets orbiting most M-dwarfs are not likely to host life, and that the highest probability of complex biospheres is for planets around K- and G-type stars.  The analysis suggests that the current existence of life near the Sun is slightly unusual, but not significantly anomalous.


1710.11136
Linear models for systematics and nuisances
Luger, Foreman-Mackey, Hogg

The target of many astronomical studies is the recovery of tiny astrophysical signals living in a sea of uninteresting (but usually dominant) noise  In many contexts (i.e., stellar time series, or high-contrast imaging, or stellar spectroscopy), there are structured components in this noise caused by systematic effects in the astronomical source, the atmosphere, the telescope, or the detector.  More often than not, evaluation of the true physical model for these nuisances is computationally intractable and dependent on too many (unknown) parameters to allow rigorous probability inference.  Sometimes, housekeeping data --- and often the science themselves --- can be used as predictors of the systematic noise.  Linear combinations of simple functions of these predictors are often used as computationally tractable models that can capture the nuisances.  These models can be used to fit and subtract systematics prior to investigation of the signals of interest, or they can be used in a simultaneous fit of the systematics and the signals.  In this Note, show that if a Gaussian prior is placed on the weights of the linear components, the weights can be marginalized out with an operation in pure linear algebra, which can (often) be made fast.  Illustrate this model by demonstrating the applicability of a linear model for the non-linear systematics in K2 time-series data, where the dominant noise source for many stars is spacecraft motion and variability.


1710.11576
The complete ultraviolet, optical, and near-infrared light curves of the kilonova associated with the binary neutron star merger GW170817: Homogenized data set, analytic models, and physical implications
Villar, et al

The homogenized dataset includes 625 individual flux measurements spanning 0.45 yo 29.4 days post-merger, and thus has grater constrainer power for physical models than any single dataset.  Find that the data are well modeled with a three-component kilonovamodel: a "blue" lanthanide-poor component with M~0.016 Msun and v~0.27c; an intermediate opacity "purple" component with M~0.04 Msun and a v~0.14c and a "red" lanthanide-rich component with M~0.009 Msun and v~0.08c.  Further explore the possibility of eject asymmetry and its impact on the estimated parameters.  From the inferred parameters, draw conclusions about the physical mechanisms responsible for the various ejecta components, the properties of the neutron stars, and, combined with an up-to-date merger rate, the implications for r-process enrichment via this channel.  To facilitate future studies of this keystone even, make the homogenized dataset and the modeling code public.