Day 1419

Wednesday.

1805.10486
First model independent results from DAMA/LIBRA-phase2
Bernabei, et al

The first model independent results obtained by the DAMA/LIBRA-phase2 experiment are presented.  The data have been collected over 6 annual cycles corresponding to a total exposure of 1.13 ton x yr, deep underground at the Gran Sasso National Laboratory (LNGS) of the INFN.  The DAMA/LIBRA-phase2 apparatus, ~250 kg highly radio-pure NaI(TI), profits from a second generation high quantum efficiency photomultipliers and of new electronics with respect to DAMA/LIBRA-phase1.  The improved experimental configuration has also allowed to lower the software energy threshold.  New data analysis strategies are presented.  The DAMA/LIBRA-phase2 data confirm the evidence of a signal that meets all the requirements of the model independent DM annual modulation signature, at 9.5 sigma C.L. in the energy region (1-6) keV.  In the energy region between 2 and 6 keV, where data are also available from DAMA/NaI and DAMA/LIBRA-phase1 (exposure 1.33 ton x yr, collected over 14 annual cycles), the achieved C.L. for the full exposure (2.46 ton x yr) is 12.9 sigma; the modulation amplitude of the single-hit scintillation events is: (0.0103±0.0008) cpd/kg/keV, the measured phase is (145 ±5) days and the measured period is (0.999±0.001) yr, all these values are well in agreement with those expected for DM particles.  No systematics or side reaction able to mimic the exploited DM signature (i.e. to account for the whole measured modulation amplitude and to simultaneously satisfy all the requirements of the signature), has been found or suggested by anyone throughout some decades thus far.


1805.11525
Wide-area tomography of CMB lensing and the growth of cosmological density fluctuations
Peacock, Bilicki

Describe a tomographic dissection of the Planck CMB lensing data, cross-correlating this map with galaxies in different ranges of photometric z.  Use the nearly all-sky 2MPZ and WISExSCOS catalogues for z<0.35, extending to z<0.6 using SDSS.  Describe checks for consistency between the different datasets, and perform a test for possible leakage of thermal SZ signal into the cross-correlation measurements.  The amplitude of the X-correlation allows estimate of the evolution of density fluctuations as a function of z, thus providing a test of theories of modified gravity.  Assuming the common parameterization for the logarithmic growth rate, f_g=Omega_m(z)^gamma, infer gamma=0.77±0.18 when Omega_m is fixed using external data.  Thus CMB lensing tomography is currently consistent with Einstein gravity, where gamma=0.55 is expected.  Discuss how such constraints may be expected to improve with future data.

Day 1418

Tuesday.

1805.10347
The Betelgeuse Project II: astroseismology
Nance, Sullivan, Diaz, Wheeler

Explore the question of whether the interior state of massive red supergiant supernova progenitors can be effectively probed with astroseismology.  Computed a suite of ten models with ZAMS masses from 15 to 25 m_sun in intervals of 1 m_sun, including the effects of rotation, with the stellar evolutionary code MESA.  Estimate the characteristic frequencies and convective luminosities of convective zones at two illustrative stages, core helium burning and off-center convective carbon burning.  Also estimate the power that might be delivered to the surface to modulate the luminous output considering various efficiencies and dissipation mechanisms.  The inner convective regions should generate waves with characteristic periods of ~20 days in core He burning, ~10 days in He shell burning, and 0.1 to 1 day in shell C burning.  Acoustic waves may avoid both shock and diffusive dissipation relatively early in core He burning through most of the structure.  In shell C burning, years before explosion, the signal generated in the He shell might in some circumstances be weak enough to avoid shock dissipation, but is subject to strong thermal dissipation in the H envelope.  Signals from a convective C-buring shell are very likely to be even more severely damped within the envelope.  In the most optimistic case, early in core He burning, waves arriving close to the surface could represent luminosity fluctuations of a few millimagnitudes, but the conditions in the very outer reaches of the envelope suggest severe thermal damping there.


1805.10630
Predicted microlensing events from analysis of Gaia Data release 2
Bramich

Astrometric microlensing can be used to make precise measurements of the masses of lens stars that are independent of their assumed internal physics.  Such direct mass measurements, obtained purely by observing the gravitational effects of the stars on external objects, are crucial for validating theoretical stellar models.  Specifically, astrometric microlensing allows direct mass measurements of single stars for which so few measurements exist.  To use the astrometric solutions and photometric measurements of ~1.7 billion stars from Gaia DR2 to predict microlensing events during the nominal Gaia mission and beyond.  This will enable astronomers to observe the entirety of each event with appropriate observing resources.  The data will allow precise lens mass measurements for white dwarfs and low-mass main sequence stars helping to constrain stellar evolutionary models.  Search for source-lens pairs in GDR2 that could lead to events between 25/7/3014 and 25/07/2026.  Estimate lens masses using GDR2 photometry and parallaxes, and appropriate model isochrones.  Combined with source and lens parallax measurement from GDR2, this allows the Einstein radius to be computed for each pair.  By considering the paths on the sky, calculate the microlensing signals that are to be expected.  Present a list of 76 predicted microlensing events.  9 and 5 astrometric events will be caused by LAWD37 and Stein2051B.  9 events will exhibit detectable photometric and astrometric signatures.  Of the remaining events, ten will exhibit astrometric signals with amplitudes above 0.5 mas, while the rest are low-amplitude astrometric events with amplitudes between 0.131 and 0.5 mas.  5 and 2 events will reach their peaks during 2018 and 2019.  5 of the photometric events have the potential to eveolve into high-magnitfication events, which may also probe for planetary companions to the lenses.


1805.10944
Impact of filaments on galaxy formation in their residing dark matter haloes
Liao, Gao

Make use of a high-resolution zoom-in hydrodynamical simulation to investigate the impact of filaments on galaxy formation in their residing DM haloes.  A method based on the density field and the Hoshen-Kopelman algorithm is developed to identify filaments.  Show that cold and dense gas preprocessed by DM filaments can be further accreted into residing individual low-mass haloes in directions along the filaments.  Consequently, comparing with field haloes, gas accretion is very anisotropic for filament haloes.  About 30-40 percent of the accreted gas of a residing filament halo was preprocessed by filaments, leading to 2 different thermal histories for the gas in filament haloes.  Filament haloes have higher baryon and stellar fractions when comparing with their field counterparts.  The results suggest that filaments assist gas cooling and enhance star formation in their residing DM haloes.

Day 1417

Thursday.  Friday.  Monday.

1805.09000
The impact of the cosmic variance on $H_0$ on cosmological analyses
Camarena, Marra

The current 3.4 sigma tension between local (1604.01424) and global (1605.02985) measurements of H_0 cannot be fully explained by the concordance LCDM model.  It could be produced by unknown systematics or by physics beyond the standard model.  In particular, non-standard DE models were shown to be able to alleviate this tension.  On the other hand, it is well known that linear perturbation theory predicts a cosmic variance on the Hubble parameter H_0, which leads to systematic errors on its local determination.  Here, study how including in the likelihood the cosmic variance on H_0 affects statistical inference.  In particular, consider the gammaCDM, wCDM and gamma w CDM parametric extensions of the standard model, which is constrained with CMB, BAO, NSeIa, RSD and H_0 data.  Learn two important lessons.  First, the systematic error from cosmic variance is -- independently of the model - approximately sigma_cv ~ 2 km/s/Mpc and of the same order of the uncertainty 1.74 km/s/Mpc on local H_0.  Taking into account cosmic variance, the tension is reduced to 2.4 sigma so that the cosmology-independent estimate by Riess+ (1604.01424) can be included in cosmological analyses without the risk of artificially biasing the results.  Second, cosmic variance, besides shifting the constraints, can drastically change the results of model selection: much of the statistical advantage of non-standard models is to alleviate the now-reduced tension.  Conclude that it is crucial to include the cosmic variance on H_0 if one wants to use the local determination of the Hubble constant by Riess+.  Doing the contrary could potentially bias the conclusions.

Day 1416

Wednesday.

1805.08252
Tale of stable interacting dark energy, observational signatures, and the $H_0$ tension
Yang, et al

Investigate the observational consequences of a novel class of stable interacting dark energy (IDE) models, featuring interactions between DM and DE.  In the first part of the work, start by considering two IDE models which are known to present early-time linear perturbation instabilities.  Applying a transformation depending on the DE EoS to the DM-DE coupling, then obtain two novel stable IDE models.  Subsequently, derive robust and accurate constraints on the parameters of these models, assuming a constant EoS $w_x$ for the DE fluid, in light of some of the most recent publicly available cosmological data.  These include CMB temperature and polarization anisotropy measurements from the Planck satellite, a selection of BAO measurements, SNIa luminosity distance measurements from the JLA sample, and measurements of the Hubble parameter up to redshift 2 from cosmic chronometers.  The analysis displays a mild preference for the DE fluid residing in the phantom region (w_x<-1), with significance up to 95% confidence level, while obtaining new upper limits on the coupling parameter between the dark components.  The preference for a phantom DE suggests a coupling function Q<0, thus a scenario where energy flows from the DM to the DE.  Also examine the possibility of addressing the H_0 and sigma_8 tensions, finding that only the former can be partially alleviated.  Finally, perform a Bayesian model comparison analysis to quantify the possible preference for the two IDE models against the standard concordance LCDM model, finding that the latter is always preferred with the strength of the evidence ranging from positive to very strong.


1805.08682
The peculiar shapes of Saturn's small inner moons as evidence of mergers of similar-sized moonlets
Leleu, Jutzi, Rubin

The Cassini spacecraft revealed the spectacular, highly irregular shapes of the small inner moons of Saturn, ranging from the unique "ravioli-like" forms of Pan and Atlas to the highly elongated structure of Prometheus.  Closest to Saturn, these bodies provide important clues regarding the formation process of small moons in close orbits around their host planet, but their range of irregular shapes has not been explained yet.  Here, show that the spectrum of shapes among Saturn's small moons is a natural outcome of merging collisions among similar-sized moonless possessing physical properties and orbits that are consistent with those of the current moons.  A significant fraction of such merging collisions take place either at the first encounter or after 1-2 hit-and-run events, with impact velocities in the range of 1-5 times the mutual escape velocity.  Close to head-on mergers result in flattened objects with large equatorial ridges, as observed on Atlas and Pan.  With slightly more oblique impact angles, collisions lead to elongated, Prometheus-like shapes.  These results suggest that the current forms of the small moons provide direct evidence of the processes at the final stages of their formation, involving pairwise encounters of moonlets of comparable size.  Finally, show that this mechanism may also explain the formation of Iapetus' equatorial ridge, as well as its oblate shape.

Day 1415

Monday, Tuesday.

1805.06799
Radio galaxy shape measurement wit Hamiltonian Monte Carlo in the visibility domain
Rivi, Lochner, Balan, Harrison, Abdalla

Radio WL, while a highly promising complementary probe to optical WL, will require incredible precision in the measurement of galaxy shape parameters.  In this paper, extend the Bayesian Inference for Radio Observations model fitting approach to measure galaxy shapes directly from visibility data of radio continuum surveys, instead of from image data.  Apply a Hamiltonian Monte Carlo (NMC) technique for sampling the posterior, which is more efficient than the standard MCMC method when dealing with a large dimensional parameter space.  Adopting the exponential profile for galaxy model fitting allows analytical calculation of the likelihood gradient required by HMC, allowing a faster and more accurate sampling.  The method is tested on SKA1-MID simulated observations at 1.4 GHz of a field containing up to 1000 star-forming galaxies.  It is also applied to a simulated observation of the WL precursor survey SuperCLASS.  In both cases obtain reliable measurements of the galaxies' ellipticity and size for all sources with SNR >=10, and also find relationships between the convergence properties of the HMC technique and some source parameters.  Direct shape measurement in the visibility domain achieves high accuracy at the expected source number densities of the current and next SKA precursor continuum surveys.  The proposed method can be easily extended for the fitting of other galaxy and scientific parameters, as well as simultaneously marginalizing over systematic and instrumental effects.


1805.06804
Does GW170817 falsify MOND?
Sanders

The gravitational-wave event GW170817 and the near-simultaneous corresponding gamma-ray burst (GRB 170817A) falsify modified gravity theories in which the gravitational geometry differs non-conformally from physical geometry.  Thus, the observations of this event definitively rule out theories, such as TeVeS, a suggested relativistic extension of Milgrom's modified Newtonian dynamics (MOND), that predict a significantly different Shapiro delay for EM and gravitational radiation.  While not falsifying MOND per se, GW170817 severely constrains relativistic extension of MOND to theories that do not rely on additional matter-coupling fields but rather upon modified field equations for one universal gravitational and physical metric.  Here, mention a simple preferred-frame theory as an example.


1805.06938
The impact of assembly bias on the halo occupation in hydrodynamical simulations
Artale, Zahavi, Contreras, Norberg

Investigate the variations in galaxy occupancy of the DM haloes with the LS environment and halo formation time, using two state-of-the-art hydro cosmo sims, EAGLE and Illustris.  For both simulations, use 3 galaxy samples with a fixed number density ranked by stellar mass.  For these samples, find that low-mass haloes in the most dense environments are more likely to host a central galaxy than those in the least dense environments.  When splitting the halo population by formation time, these relations are stronger.  Hence, at fixed low halo mass, early-formed haloes are more likely to host a central galaxy than late-formed haloes since they have had more time to assemble.  The satellite occupation shows a reverse trend where early-formed haloes host fewer satellites due to having more time to merge with the central galaxy.  Also analyse the stellar mass -- halo mass relation for central galaxies in terms of the LS environment and formation time of the haloes.  Find that low mass haloes in the most dense environment host relatively more massive central galaxies.  This trend is also found when splitting the halo population by age, with early-formed haloes hosting more massive galaxies.  The results are in agreement with previous findings form SAMs, providing robust predictions for the occupancy variation signature in the HOD of galaxy formation models.


1805.06976
Cosmological cluster tension
Blanchard, Sakr, Ilic

The abundance of clusters is a classical cosmological probe sensitive to both the geometrical aspects and the growth rate of  structures.  The abundance of clusters of galaxies measured by Planck has been found to be in tension with the prediction of the LCDM models normalized to Planck CMB fluctuations power spectra.  The same tension appears with X-ray cluster local abundance.  Massive neutrinos and modified gravity are two possible solutions to fix this tension . Alternatively, others options include a bias in the selection procedure or in the mass calibration of clusters.  Present a study, based on the recent work, updating the present situation on this topic and discuss the likelihood of the various options.

Day 1414

Friday.


1805.05481
Image simulations for gravitational lensing with SkyLens
Plazas, Meneghetti, Maturi, Rhodes

Present the latest version of the ray-tracing simulation code Skylens, which can be used to develop image simulations that reproduce SL observations by any mass distribution with a high level of realism.  Improvements of the code with respect to previous versions include the implementation of the multi-lens plane formalism, the use of denoised source galaxies from the Hubble eXtreme Deep Field, and the simulation of substructures in lensed arcs and images, based on a morphological analysis of bright nearby galaxies.  Skylens can simulate observations with virtually any telescope.  Present examples of space- and ground-based observations of a galaxy cluster through WFC/ACS (HST), NIC (JWST), WFI (WFIRST), HSC (Subaru), and the VIS (Euclid).


1805.05741
Search for $\gamma$-ray line signals from dark matter annihilations in the inner Galactic halo from ten years of observations with H.E.S.S
H.E.S.S. Collaboration

Spectral lines are among the most powerful signatures of DM annihilation searches in very high-energy gamma rays.  The central region of the MW halo is one of the most promising targets given its large amount of DM and proximity to Earth.  Report on a search for a mono energetic spectral line from self-annihilations of DM particles in the energy range from 300 GeV to 70 TeV using a 2d maximum likelihood method taking advantage of both the spectrand and spatial features of signal versus background.  The analysis makes use of GC observations accumulated over 10 years with the HESS array of ground-based Cherenkov telescopes.  No significant gamma-ray excess above the background is found.  Derive upper limits on the annihilation cross section <sigma_v> for mono energetic DM lines at the level of ~4e-28 cm^3 /s at 1TeV, assuming an Einasto DM profile for the MW halo.  For a DM mass of 1TeV, they improve over the previous ones by a factor of 6.  The present constraints are the strongest obtained so far for DM particles in the mass range 300 GeV-70 TeV.  Ground-based gamma-ray observations have reached sufficient sensitivity to explore relevant velocity-averaged cross sections for DM annihilation into 2 gamma-ray photons at the level expected from the thermal relic density for TeV DM particles.


1805.06479
GalWeight: a new and effective weighting technique for determining galaxy cluster and group membership
Abdullah, Wilson, Klypin

Introduce GalWeight, a new technique for assigning galaxy cluster membership.  This technique is specifically designed to simultaneously maximize the number of bona fide cluster members while minimizing the number of contaminating interlopers.  The GalWeight technique can be applied to both massive galaxy clusters and poor galaxy groups.  Moreover, it is effective in identifying members in both the virial and infall regions with high efficiency.  Apply the GalWeight technique to MDPL2 & Bolshoi N-body sims, and find that it is >98% accurate in correctly assigning cluster membership.  Show that GalWeight compares very favorably against four well-known exist cluster membership techniques (shifting dapper, den Hartog, caustic, SIM).  Also apply the GalWeight technique to a sample of twelve Abell clusters (including the Coma cluster) using observations from SDSS.  End by discussing GalWeight's potential for other astrophysical applications.


1805.06508
Sex-disaggregated systematics in Canadian Term Allocation Committee telescope proposal reviews
Spekkens, Cofie, Crabtree

Recent studies have shown that the proposal peer review processes employed by a  variant of organizations to allocate astronomical telescope time produce outcomes that are systematically biased depending on whether proposal's principal investigator (PI) is a man or a woman.  Using CFHT and Gemini Observatory proposal statistics from Canada over 10 recent proposal cycles, assess whether or not the mean proposal scores assigned by the NRC''s Candan Time Allocaiton Committee (CanTAC) also correlate significantly with PI sex.  Classical t-tests, bootstrap and jackknife replications show that proposal submitted by women were rated significantly worse than those submitted by men.  Subdivide the data in order to investigate sex-disaggregated statistics in relation to PI carrier stage (faculty vs. non-faculty), telescope requested, scientific review panel, observing semester, and the PhD year of faculty PIs.  Consistent with the bivalent results, a multivariate regression analysis controlling for other covariances confirmed that PI sex is the only significant predictor of proposal rating scores for the sample as a whole, although differences emerge for proposals submitted by faculty and non-faculty PIs.  While further research is needed to explain the results, it is possible that implicit social cognition is at work. NRC and CanTAC have taken steps to mitigate this possibility by altering proposal author lists in order to conceal the PI's identity among co-investigators.  Recommend that the impact of this measure on mitigating bias in future observing semesters by quantitatively assessed using statistical techniques such as those employed here.

Day 1413

Thursday.

1805.05966
The onset of star formation 250 million years after the Big Bang
Hashimoto, et al

A fundamental quest of modern astronomy is to locate the earliest galaxies and study how they influenced the intergalactic medium a few hundred million years after the Big Bang.  The abundance of star-forming galaxies is known to decline from redshifts of about 6 to 10, but a key question is the extent of SF at even earlier times, corresponding to the period when the first galaxies might have emerged.  Present spectroscopic observations of MACS1149-JD1, a gravitationally lensed galaxy observed when the Universe was less than 4% of its present age.  Detect an emission line of doubly ionized oxygen at a z of 9.1096±0.0006, with an uncertainty of one standard deviation.  This precisely determined redshift indicates that the red rest-frame optical color arises from a dominant stellar component that formed about 250 million years after the Big Bang, corresponding to a redshift of about 15.  The results indicate that it may be possible to detect such early episodes of SF in similar galaxies with future telescopes.

Day 1412

Wednesday.

1805.05051
A likely super massive black hole revealed by its Einstein radius in Hubble Frontier Fields Images
Chen, Broadhurst, et al

At cosmological distances, gravitational lensing can provide a direct measurement of SMBH masses irrespective of their luminosities.  When the BG lensed and FG lensing galaxies are well aligned, an inherent degeneracy with the mass profile of the lensing galaxy means that only constraints are possible on its SMBH mass.  Here, directly measure the mass of a SMBH in the BCG of MACS J1149.5+2223 at z=0.5 through one of the multiply-lensed images of a BG spiral galaxy at z=1.49 projected close to the BCG.  In this particular image, an intrinsically compact region in one of the spiral arms is lensed into an arc that curves towards the BCG center.  Crucially, this arc has a radius of curvature of only ~0.6", betraying the presence of a local compact deflector.  Its curvature is most simply reproduced by a point-like object with a mass of (8.4+4.3-1.8)e9Msun, similar to SMBH masses in local elliptical galaxies having comparable luminosities.  The SMBH is noticeably offset by 4.4±0.3 kpc from the BCG light centre, plausibly the result of a kick imparted ~2.8e7 years ago during the merger of two SMBHs, placing it just beyond the stellar core.  A similar curvature can be produced by replacing the offset SMBH with a compact galaxy having a mass of ~2e10 Msun within a cutoff radius of <4 kpc, and an unusually large M/L>50(M/L)_sun to make it undetectable in the deep Hubble Frontiers Fields image, at or close to the cluster redshift; such a lensing galaxy, however, perturbs other nearby lensed features of the spiral galaxy in an undesirable manner.


1805.05484
The C-Band All-Sky Survey (C-BASS)
Taylor

An experiment to image the whole sky in intensity and polarization at 5 GHz (where the synchrotron radiation is the dominant emission mechanism).  The primary aim of C-BASS is to provide low-frequency all-sky maps of he Galactic emission which will enable accurate component separation analysis of both existing and future CMB intensity and polarization imaging surveys.  Here, present an overview of the experiment and an update on the current status of observations.  Present simulation results showing the expected improvement in the recovery of CMB and foreground signals when including C-BASS data as an additional low-frequency channel, both for intensity and polarization.  Also present preliminary results from the northern part of the sky survey.


1805.05834
Using Deep Space Climate Observatory Measurements to study the Earth as an Exoplanet
Jiang, et al

Even though it was not designed as an exoplanetary research mission, the Deep Space Climate Observatory (DSCOVR) has been opportunistically used for a novel experiment, in which Earth serves as a proxy exoplanet.  More than 2 years of DSCOVR Earth images were employed to produce time series of multi-wavelength, single-point light sources, in order to extract information on planetary rotation, cloud patterns, surface type, and orbit around the Sun.  In what follows, assume that these properties of the Earth are unknown, and instead attempt to derive them from first principles.  These conclusions are then compared with known data about our planet.  Also used the DSCOVR data to simulate phase angle changes, as well as the minimum data collection rate needed to determine the rotation period of an exoplanet.  This innovative method of using the time evolution of a multi-wavelength, reflected single-point light source, can be deployed for retrieving a range of intrinsic properties of an exoplanet around a distant star.

Day 1411

Tuesday.

1805.04716
Are $H_0$ and $\sigma_8$ tensions generic to present cosmological data?
Bhattacharyya, et al

Yes, for a wide range of cosmological models (LCDM, non-interacting w_zCDM or models with possible interactions between DE and DM, in either phantom or non-phantom regimes).  In the recent past there have been many attempts to solve the tension between direct measurements of H_0 and sigma_8 sqrt(Omega_0m} from the respective low z observables and indirect measurements of these quantities from the CMB.  In this work, reconstruct a model independent approach that boils down to different classes of cosmological models under suitable parameters choices.  Test this parameterization against the latest Planck CMB data combined with recent BAO, SNeIa datasets and the R16 direct H_0 measurements, and compare among different cosmological models.  The analysis reveals that a strong positive correlation between H_0 and sigma_8 is more or less generic, irrespective of the choice of cosmological models.  Also find that present data slightly prefers a phantom equation of state for DE and a slight negative value for effective equation of state for DM (which is a direct signature of interaction models) with a relatively high value for H_0 consistent with R16 and simultaneously, a consistent value for Omega_0m.  Thus, even though the tensions cannot be fully resolved, interaction models with phantom equation of state get a slight edge over the others for currently available data.  Also see that allowing interaction between DE and DM may resolve the tension between the high z CMB data and individual low z datasets, but the low z datasets have inconsistencies between them (e.g. between BAO and H_0, SNeIa and BAO, and cluster counts and H_0) that are practically independent of the cosmological model.


1805.05037
Chemical characterization of the inner galactic bulge:North-South symmetry
Nandakumar, et al

...With the caveat of a relatively small sample, do not find significant differences in the chemical abundance between the Norther and the Southern fields, hence the evidence is consistent with symmetry in chemistry between North and South.


1805.05146
Breaking degeneracies in modified gravity with higher (than 2nd) order weak-lensing statistics
Peel, Pettorino, Giocoli, Starck, Baldi

GR has been well tested up to solar system scales, but it is much less certain that standard gravity remains an accurate description on the largest, i.e. cosmological, scales.  Many extensions to GR have been studied that are not yet ruled out by the data, including by that of the recent direct gravitational wave detections.  Degeneracies among the standard model (LCDM) and modified gravity (MG) models, as well as among different MG parameters, need to be addressed in order to best exploit information from current and future surveys and to unveil the nature of DE.  Propose various higher-order statistics in the WL signal as a new set of observables able to break degeneracies between massive neutrinos and MG parameters.  Test the methodology on so-called f(R) models, which constitute a class of viable models that can explain the accelerated universal expansion by a modification of the fundamental gravitational interaction.  Explore a range of these models that still fit current observations at the background and linear level, and show using numerical simulations that certain models which include massive neutrinos are able to mimic LCDM in terms of the 3d PS of matter density fluctuations.  Find that depending on the redshift and angular scale of observations, non-Gaussian information accessed by higher-order WL statistics can be used to break the degeneracy between f(R) models and LCDM.  In particular, peak counts computed in aperture mass maps outperform third- and fourth-order moments.

Day 1410

Monday.

1805.03254
Implication of the shape of the EDGES signal for the 21cm power spectrum
Kaurov, Venumadhav, Dai, Zaldarriaga

Revisit the 21cm PS from the epoch of cosmic dawn in light of the recent EDGES detection of the 21cm global signal at frequencies corresponding to z~20. The shape of the signal suggests that the spin temperature of neutral hydrogen was coupled to the kinetic temperature of the gas relatively rapidly (19<~z<~21).  Therefore consider models in which the UV photons were dominantly produced in the rarest and most massive haloes (M>~1e9Msun), since their abundance grows fast enough at those redshifts to account for this feature of the signal.  Show that these models predict large power spectrum amplitudes during the inhomogeneous coupling, and then inhomogeneous heating by CMB and Ly-a photons due to the large shot noise associated with rare sources.  The PS is enhanced by more than an order of magnitude compared to previous models which did not include the shot noise contribution, making it a promising target for upcoming radio interferometers that aim to detect high-redshift 21cm fluctuations.


1805.04114
The correspondence between convergence peaks from weak lensing and massive dark matter haloes
Wei, et al

The convergence peaks, constructed from galaxy shape measurement in WL, is a power probe of cosmology as the peaks can be connected with the underlined DM haloes.  However, the capability of convergence peak statistic is affected by the noise in galaxy shape measurement, signal to noise ratio as well as the contribution form the projected mass distribution from the LSS along the LoS.  In this paper, use the ray-tracing sim on a curved sky to investigate the correspondence between the convergence peak and the DM haloes at the LoS.  Find that, in case of no noise and for source galaxies at z_s=1, more than 65% peaks with SNR >=3 are related to more than one massive haloes with mass larger than 1e13 Msun.  Those massive haloes contribute 87.2% to high peaks (SNR>=5) with the remaining contributions are form the LSS.  In the noise field where the shape noise is modeled as a gaussian distribution, about 60% high peaks (SNR>=5) are true peaks and the fraction decreases to 20% for lower peaks (3<= SNR <5).  Furthermore, find that high peaks (SNR>=5) are dominated by very massive haloes larger than 1e14Msun.


1805.04511
Cosmological simulations for combined-probe analyses: covariance and neighbor-exclusion bias
Harnois-Deraps, et al

Present a public suite of WL mock data, extending the SLICS (Scinet Light Cone Simulations) to simulate cross-correlation analyses with different cosmological probes.  These mocks include KIDS-450- and LSST-like lensing data, CMB lensing maps and simulated spectroscopic surveys that emulate the GAMA, BOSS and 2dFLenS galaxy surveys.  With 817 independent realizations, the mocks are optimized for combined-probe covariance estimation, which is illustrated for the case of a joint measurement involving cosmic shear, gg lensing and galaxy clustering form KiDS-450 and BOSS data.  With their high spatial resolution, the SLICS are also optimal for predicting the signal for novel lensing estimators, for the validation of analysis pipelines, and for testing a range of systematic effects such as the impact of neighbour-exclusion bias on the measured tomographic cosmic shear signal. For surveys like KiDS and DES, where the rejection of neighboring galaxies occurs within ~2 arc seconds, show that the measured cosmic shear signal will be biased low, but by less than a percent on the angular scales that are typically used in cosmic shear analyses.  The amplitude of the neighbor exclusion bias doubles in deeper, LSST-like data.  The simulation predicts described in this paper are made available at http://slicks.roe.ac.uk.

Day 1409

Friday.

1805.03672
Verifications of scaling relations useful for the intrinsic alignment self-calibration
Meng, Yu, Zhang, Jing

IA is a major challenge of WL cosmology.  To alleviate this problem, Zhang 2010 proposed a self-calibration method, independent of IA modeling.  This proposal relies on several scaling relations between 2pt clustering of IA and matter/galaxy fields, which were previously only tested with analytical IA models.  In this paper, these relations are tested comprehensively with a N-body sim of 2073^3 sim particles and box size 600 Mpc/h.  They are verified at the accuracy level of O(1)% over angular scales and source redshifts of interest.  Further confirm that these scaling relations are generic, insensitive to halo mass, weighting in defining halo ellipticities, photo-z error, and mis-alignment between galaxy ellipticities and halo ellipticities.  Also present and verify 3 new scaling relations on the B-mode IA.  These results consolidate and complete the theory side of the proposed self-calibration technique.


1805.04004
The dearth of difference between central and satellite galaxies I. Perspectives on star formation quenching and AGN activities
Wang, .. Mo, ... van den Bosch, et al

Investigate the quenching properties of central and satellite galaxies, utilizing the halo masses and central-satellite identifications from the SDSS galaxy group catalog of Yang+.  Find that the quenched fractions of centrals and satellites of similar stellar masses have similar dependence on host halo mass.  The similarity of the two populations is also found in terms of sSFR and 4000A break.  The quenched fractions of centrals and satellites of similar masses show similar dependencies on bulge-to-total light ratio, central velocity dispersion and halo-centric distance in halos of given halo masses.  The prevalence of optical/radio-lound AGNs is found to be similar for centrals and satellites at given stellar masses.  All these findings strongly suggest that centrals and satellites of similar masses experience similar quenching processes in their host halos.   Discuss implications of the results for the understanding of galaxy quenching.

Day 1408

Tuesday, Wednesday, Thursday.

1805.02427
Star-galaxy classification in the Dark Energy Survey Y1 dataset
Sevilla-Noarbe, et al

Perform a comparison of different approaches to star-galaxy classification using the broad-band photometric data from Year 1 of DES.  This is done by performing a wide range of tests with and without external 'tough' information, which can be ported to other similar datasets.  Make a broad evaluation of the performance of the classifiers in two science cases with DES data that are most affected by this systematic effect: LSS and MW studies.  In general, even though the default morphological classifiers used for DES Y1 cosmology studies are sufficient to maintain a low level of systematic contamination from stellar mis-classification, contamination can be reduced to the O(1%) level by using multi-epoch and infrared information from external datasets.  For MW studies the stellar sample can be augmented by ~20% for a given flux limit.  Reference catalogs used in this work will be made available upon publication.


1805.02662
Detecting strongly lensed supernovae at z~5-7 with LSST
Rydberg, et al

Find that LSST main survey could detect ~1-2 lensed Pop III SN but 130-1400 Pop I/II SNe.  An alternative deep survey with a one-year cadence could find ~10 Pop III SNe with an 84h exposure and ~50 SNe with a 420h exposure.


1805.01448
The missing satellites of the Magellanic Clouds? Gaia proper motions of the recently discovered ultra-faint galaxies
Kallivayalil, et al

According to LCDM theory, hierarchical evolution should occur on all mass scales, implying that satellites of the MW also once had companions.  The recent discovery of several ultra-faint dwarf galaxy candidates in close proximity to the MCs provides a unique opportunity to test this theory.  Specifically, proper motions provide a stringent test, because material that is associated with the LMC prior to infall should retain its direction of orbital angular momentum.  Present proper motion measurements for the 13 of the 32 newly discovered dwarf galaxy candidates using Gaia DR2.  All 13 also have radial velocity measurements.  Compare the measured 3d velocities of these dwarfs to those expected at the corresponding distance and location for the debris of an LMC analog in a numerical simulation.  Conclude that 4 of these galaxies (Hor1, Car2, Car3 and Hyd1) have come in with the MC system, consituting the first confirmation of the type of satellite infall predicted by LCDM.  Ret2, Tuc2 and Gru1 have some velocity components that are not consistent within 3 sigma of the predictions and are therefore less favorable. Hyd2 and Dra2 could be associated with the LCMD and merit further attention.  Rule out TUc3, Cra2, Tri2 and Aqu2 as potential members.  Of the dwarfs without measured PMs, 6 of them are deemed unlikely on the bases of their positions and distances alone which put them too far from the orbital plane expected for LMC debris (Eri2, Ind2, Cet2, Tri2, Cet3 and Vir1).  For the remaining sample use the simulation to predict proper motions and radial velocities, finding that Phx2 has an overdensity of stars in DR2 consistent with this PM prediction.  If this radial velocity is confirmed at ~-15 km/s, it is also likely a member.


1805.01421
Concerns about modeling of foregrounds and the 21-cm signal in EDGES data
Hills, et al

Re-analyzed the data in which Bowman+2018 identified a feature that could be due to cosmological 21-cm line absorption in the IGM at z~17.  If using exactly their procedures, then find almost identical results, but the fits imply either non-physical properties for the ionosphere or unexpected structure in the spectrum of foreground emission (or both).  Furthermore, find that making reasonable changes to the analysis process, e.g., altering the description of the foregrounds or changing the range of frequencies included in the analysis, gives markedly different results for the properties of the absorption profile.  Can in fact get what appears to be a satisfactory fit to the data without any absorption feature if there is a periodic feature with an amplitude of ~0.05K present in the data.  Believe that this calls into question the interpretation of these data as an unambiguous detection of the cosmo 21-cm absorption signature.


1805.01897
Solar colorna heating by the axion quark nugget dark matter
Raza, van Waerbeke, Zhitnitsky

Astrophysics faces two 80 yr old mysteries: the nature of DM, and the high temperature of the million degree solar corona, radiating an extreme UV (EUV) excess of 1e27 erg/s.  The current paradigm is that the corona is heated by hypothetical nano-flares of unknown origin.  Recently, in Zhitnitsky 2017 it was suggested that the nano flares can be identified wit the nuggets from the Axion Quark Nugget (AQN) DM model.  This model was invented as an explanation of the observed ratio Omega_dark ~ Omega_visible, and has no free parameter other than the Axion mass.  It is proposed that the AQN particles moving through the coronal plasma (and annihilating) can both explain the EUV excess and drastic changes of the temperature in the Transition Region.  To test this proposal, performed detailed numerical simulations with a realistic AQN particle distribution and physical environment.  Remarkably, the calculations predict the correct energy budget for the solar corona, and an energy injection altitude in agreement with the temperature and mass density profile of the solar atmosphere.  Therefore, propose that the two 80 yr old mysteries could be two sides of the same coin.  Make several predictions based on this proposal that can be tested by the upcoming NASA mission the Parker Solar Probe.


1805.02649
Time evolution of intrinsic alignments of galaxies
Schmitz, Hirata, Blazer, Krause

IA, correlations between the intrinsic shapes and orientations of galaxies on the sky, are both a significant systematic in WL and a probe of the effect of LSS on galactic structure and angular momentum.  In the era of precision cosmology, it is thus especially important to model IA with high accuracy.  Efforts to use cosmological perturbation theory to model the dependence of IA on the LSS have thus far been relatively successful; however, extant models do not consistently account for time evolution.  In particular, advection of galaxies due to peculiar velocities alters the impact of IA, because galaxy positions when observed are generally different from their positions at the epoch when IA is believed to be set.  In this work, evolve the galaxy IA from the time of galaxy formation to the time at which they are observed, including the effects of this advection, and show how this process naturally leads to a dependence of IA on the velocity shear.  Calculate the galaxy-galaxy-IA bispectrum to tree level (in the linear matter density) in terms of the evolved IA coefficients.  Then discuss the implications for WL systematics as well as for studies of galaxy formation and evolution.  Find that considering advection introduces non locality into the bispectrum, and that the degree of non-locality represents the memory of a galaxy's path from the time of its formation to the time of observations.  Discuss how this result can be used to constraint the redshift at which IA is determined and provide Fisher estimation for the relevant measurements using the example of SDSS-BOSS.


1805.03394
Unidentified quasars among stationary objects from Gaia DR2
Heintz, et al

Apply a novel technique selecting quasar candidates purely as sources with zero proper motions in the Gaia data release 2 (DR2).  Demonstrate that this approach is highly efficient toward high Galactic latitudes with <25% contamination from stellar sources.  Such a selection technique offers a very pure sample completeness, since all cosmological point sources are selected regardless of their intrinsic spectral properties within the limiting magnitude of Gaia.  Carry out a pilot study by defining a sample compiled by including all Gaia-DR2 sources within one degree of the NGP selected to have proper motions consistent with zero within 2-sigma uncertainty.  By cross-matching the sample to the optical SDSS and the mid-infrared AllWISE photometric catalogues, investigative the colors of each of the sources.  Together with already spectroscopically confirmed quasars, able to determine the efficiency of the selection.  The majority of the zero proper motion sources have optical to mid-infrared colors consistent with known quasars.  The remaining population may be contaminating stellar sources, but some may also be quasars with colors similar to stars.  Spectroscopic follow-up of the zero proper motion sources is needed to unveil such a hitherto hidden quasar population.  This approach has the potential to allow substantial progress on many important questions concerning quasars such as determining the fraction of dust-obscured quasars, the fraction or broad absorption line (BAL) quasars, and the metallicity distribution of damped Lyman-alpha absorbers.  The technique could also potentially reveal new types of quasars or even new classes of cosmological point sources.

Day 1407

Thursday (3 May 2018), Friday, Monday.

1805.00021
Constraining non-cold dark matter models with the global 21-cm signal
Schneider

Any particle DM scenario featuring a suppressed power spectrum of astrophysical relevance results in a delay of galaxy formation.  As a consequence, such scenarios can be constrained using the global 21-cm absorption signal initiated by the UV radiation of the first stars.  The Experiment to Detect the Global Epoch of Reionization Signature (EDGES) recently reported the first detection of such an absorption signal at redshift ~17.  While its amplitude might indicate the need for new physics, solely focus on the timing of the signal to test non-cold DM models.  Assuming a conservative upper limit for star-formation based on radiation-hydrodynamics simulations, able to derive unprecedented constraints on a variety of non-cold DM models.  For example, the mass of thermal warm DM is limited to m_TH>6.1 keV, while mixed DM scenarios (featuring a cold and hot component) are constrained to a hot DM fraction below 17 %.  The ultra-light axion DM model is limited to masses m_a>8e-21 eV, a regime where its wave-like nature is pushed far below the kilo parsec scale.  Finally, sterile neutrinos from resonant production can be fully disfavored as a dominant DM candidate.  The results of this paper show that the 21cm absorption signal is a powerful discriminant of non-CDM, allowing for significant improvements over to the strongest current limits.  Confirming the result from EDGES is paramount in this context.


1805.00159
Detecting galaxy-filament alignments in the Sloan Digital Sky Survey III
Chen, Ho, Blazek, He, Mandelbaum, Melchior, Singh

Previous studies have shown the filamentary structures in the cosmic web influence the alignments of nearby galaxies.  Study this effect in the LOWZ sample of SDSS using the Cosmic Web Reconstruction filament catalogue of Chen+2016.  Find that LOWZ galaxies exhibit a small but statistically significant alignment in the direction parallel to the orientation of nearby filaments.  This effect is detectable even in the absence of nearby galaxy clusters, which suggests it is an effect from the matter distribution in the filament.  A nonparametric regression model suggests that the alignment effect with filaments extends over separations of 30-40 Mpc.  Find that galaxies that are bright and early-forming align more strongly with the directions of nearby filaments than those that are faint and late-forming; however, trends with stellar mass are less statistically significant, within the narrow range of stellar mass of this sample.


1804.11339
Ghostly tributaries to the Milky Way: Charting the Halo's stellar streams with the Gaia DR2 catalogue
Malhan, Ibata, Martin

Present a panoramic map of the stellar streams of the Milky Way based upon astrometric and photometric measurements from the Gaia DR2 catalogue.  In this first contribution, concentrate on the halo at heliocentric distances beyond 5 kpc, and at Galactic latitudes |b|>30 deg, using the STREAMFINDER algorithm to detect structures along plausible orbits that are consistent with the Gaia proper motion measurements.  Find a rich network of criss-crossing streams in the halo, often with striking kinematic coherence.  Some of these structures were previously-known, several are new discoveries, but others are potentially artifacts of the Gaia scanning law and will require confirmation.  With these initial discoveries, starting to unravel the complex formation of the halo of our Galaxy.


1805.00562
Studying galaxy roughs and ridges using weak gravitational lensing with the Kilo-Degree Survey
Brouwer, et al

Study projected under densities in the cosmic galaxy density field known as 'troughs', and their overdense counterparts, 'ridges'.  Identify these regions using a bight sample of foreground galaxies from the photometric KiDS, specifically selected to mimic the spectroscopic GAMA survey.  From an independent sample of KiDS background galaxies, measure the WL profiles of the troughs/ridges.  Quantify their lensing strength A as a function of galaxy density percentile rank P and overdensity delta, and find that the skewness in the galaxy density distribution is reflected in the total mass distribution measured by WL.  Interpret the results using the mock galaxy catalogue from MICE Grand Challenge light cone sim, and find a good agreement with observations.  Using S/N weights derived from the Scinet LightCone Simulations (SLICS) mock catalogue, optimally stack the lensing signal of KiDS troughs with an angular radius theta_A={5,10,15,20} racmin, resulting in {16.8,14.9, 10.31, 7.55} sigma detections.  Finally, select throughs using a volume-limited sample of galaxies, split into two redshift bins between 0.1<z<0.3.  For troughs/ridges with transverse comoving radius R-A=1.9 Mpc/h, find no significant difference between the comoving A'(P) and A'(delta) relation of the low- and high-redshift sample.  Using the MICE and SLICS mocks, predict that trough and ridge evolution could be detected with GL using deeper and wider lensing surveys, such as those from LSST and Euclid.


1805.01240
Statistical separation of weak gravitational lensing and intrinsic ellipticities based on galaxy color information
Tugendhat, Reischke, Schaefer

IA of galaxies are recognized as one of the most important systematic in WL surveys on small angular scales.  In the paper, investigate ellipticity correlation functions that are remeasured separately on elliptical and spiral galaxies, for which it is assumed that the generic alignment mechanisms based on tidal shearing and tidal torquing, respectively.  Including morphological information allows to find linear combinations of measured ellipticity correlation functions which suppress the gravitational lensing signal completely or which show a strongly boosted gravitational lensing signal relative to IA.  Specifically, find that (i) intrinsic alignment spectra can be measured in a model-independent way at a significance of Sigma~60 with a wide-angle tomographic survey such as Euclid's, (ii) IA model parameters can be determined at %-level precision, (iii) this measurement is not impeded by misclassifying galaxies and assuming a wrong alignment model, (iv) parameter estimation from a cleaned WL spectrum is possible with almost no bias and (v) the misclassification would not strongly impact parameter estimation from the boosted WL spectrum.

Day 1406

Monday (30 April 2018), Tuesday, Wednesday.

1804.10395
Lethal radiation from nearby supernovae helps to explain the small cosmological constant
Totani, et al

The observed value Lambda_obs of the cosmological constant Lambda is extremely smaller than theoretical expectations, and the anthropic argument has been proposed as a solution to this problem because galaxies do not form when Lambda >> Lambda_obs.  However, the contemporary galaxy formation theory predicts that stars form even when a high value of Lambda / Lambda_obs ~50, which makes the anthropic argument less persuasive.  Here, calculate the probability distribution of Lambda using a model of cosmological galaxy formation, considering extinction of observers caused by radiation from nearby supernovae.  The life survival probability decreases in a large Lambda universe because of higher stellar density.  Using a reasonable rate of lethal supernovae, find that the mean expectation value of Lambda can be close to Lambda_obs, and hence tis effect may be essential to understand the small but nonzero value of Lambda.  It is predicted that we are located on the edge of habitable regions about stellar density, which may be tested in future exoplanet studies.


1804.10401
A technique for estimating the absolute gain of a photomultiplier tube
Takahashi, et al

Detection of low-intensity light relies on the conversion of photons to photoelectron, which are then multiplied and detected as an electrical signal.  To measure the actual intensity of the light, one must know the factor by which the photoelectrons have been multiplied.  To obtain this amplification factor, we have developed a procedure for estimating precisely the signal caused by a single photoelectron.  The method utilizes the fact that the photoelectrons conform to a Poisson distribution.  The average signal produced by a single photoelectron can then be estimated from the number of noise events, without requiring analysis of the distribution of the signal produced by a single photoelectron.  The signal produced by one or more photoelectrons can be estimated experimentally without any assumptions.  This technique, and an example of the analysis of a signal from a photomultiplier tube, are described in this study.


1804.10663
Survey geometry and the internal consistency of recent cosmic shear measurements
Troxel, Krause, Chang, Eifler, et al

Explore the impact of an update to the typical approximation for the shape noise term in the analytic covariance matrix for cosmic shear experiments that assumes the absence of survey boundary and mask effects.  Present an exact expression for the number of galaxy pairs in this term based on the survey mask, which leads to more than a factor of 3 increase in the shape noise on the largest measured scales for KiDS-450 real-space cosmic shear data.  Compare the result of this analytic expression to several alternative methods for measuring the shape noise from the data and find excellent agreement.  This update to the covariance resolves any internal model tension evidenced but the previously large cosmological best-fit chi^2 for the KiDS-450 cosmic shear data.  The best-fit chi^2 is reduced from 161 to 121 for 118 degrees of freedom.  Also apply a correction to how the multiplicative shear calibration uncertainty is included in the covariance.  This change, along with a previously known update to the reported effective angular values of the data vector, jointly shift the inferred amplitude of the correlation function to higher values.  Find that this improves agreement of the KiDS-450 cosmic shear results with DES-Y1 and Planck results.

Day 1405

Wednesday (25 April 2018), Thursday, Friday.

1804.08907
Exoplanets: past, present, and future
Lee

Our understanding of extra-solar planet systems is highly driven by advances in observations in the past decade.  Thanks to high precision spectrograph, we are able to reveal unseen companions to stars with the radial velocity method.  High precision photometry from the space, especially with the Kepler mission, enables us to detect planets when they transit their stars and dim the stellar light by merely one percent or smaller.  Ultra wide-field, high cadence, continuous monitoring of the Galactic bulge from different sites around the southern hemisphere provides us the opportunity to observe microlensing effects caused by planetary systems from the solar neighborhood, al the way to the Milky Way center.  The exquisite AO imaging from ground-based large telescopes, coupled with high-contrast coronagraph, captured the photons directly emitted by planets around other stars.  In this article, Present a concise review of the extra-solar planet discoveries, discussion the strengths and weaknesses of the major planetary detection methods, providing an overview of the current understanding of planetary formation and evolution given the tremendous observations delivered by various methods, as well as on-going and planned observation endeavors to provide a clear picture of extra-solar planetary systems.


1804.07049
A predicted astrometric microlensing event by a nearby white dwarf
McGill, et al

Use the Tyco-Gaia Astrometric Solution catalogue, large of Gaia DR1, to search for candidate astrometric microlensing events expected to occur within the remaining lifetime of the Gaia satellite.  The search yielded one promising candidate.  Predict that the nearby DQ type WD LAWD 37 (WD 1142-645) will lens a background star and will reach closest approach on Nov. 11 2018 (±4 days) with impact parameter 380±10 mas.  This will produce an apparent maximum deviation of the source position of 2.8 ±0.1 mas.  In the most propitious circumstance, Gaia will be able to determine the mass of LAWD 37 to ~3%.  This mass determination will provide an independent check on atmospheric models of white dwarfs with He rich atmospheres, as well as tests of WD mass radius relationships and evolutionary theory.


1804.07401
A new approach to uncovering substructure: proof of concept using Abell 2744
Schwinn, et al

A recent comparison of the massive galaxy cluster Abell 2744 with the Millennium XXL (MXXL) N-body sims has hinted at a tension between the observed substructure distribution and the predictions of LCDM.  Follow-up investigations indicated that this could be due to the contribution from the host halo and the sub halo finding algorithm used.  To be independent of any sub halo finding algorithm, investigate the particle data of the MXXL sim directly.  Propose a new method to find substructures in 2D mass maps using a wavelet transform, which treats the sim and observations equally.  Using the same criteria to define a sub halo in observations and simulated data, find 3 Abell 2744 analogues in the MXXL sim.  Thus the observations in Abell 2744 are in agreement with the predictions of LCDM.  Investigate the reasons for the discrepancy between the results obtained from the SUBFIND and full particle data analyses.  Find that this is due to incompatible substructure definitions in observations and SUBFIND.


1804.09381
Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way
Gaia Collaboration, et al

The goal of this paper is to demonstrate the outstanding quality of the second data release of the Gaia mission and its power for constraining many different aspects of the dynamics of the satellites of the Milky Way.  Focus here on determining the proper motions of 75 Galactic globular clusters, non dwarf spheroidal galaxies, one ultra-faint system, and the Large and Small Magellanic Clouds.  Using data extracted from the Gaia archive, derive the proper motions and parallaxes for these systems, as well as their uncertainties.  Demonstrate that the errors, statistical and systematic, are relatively well understood.  Integrate the orbits of these objects in 3 different Galactic potentials, and characterize their properties.  Present the derived proper motions, space velocities, and characteristic orbital parameters in various tables to facilitate their use by the astronomical community.  The limited and straightforward analyses have allowed, for example, to (i) determine absolute and very precise proper motions for globular clusters; (ii) detect clear rotation signatures in the proper motions of at least 5 globular clusters; (iii) show that the satellites of the MW are all on high-inclination orbits, but that they do not share a single plane of motions; (iv) derive a lower limit for the mass of the Milky Way of 9.8+6.7-2.7e11 Msun based on the assumption that the Leo I dwarf spheroidal is bound; (v) derive a rotation curve for the LMC based solely on proper motions that is competitive with LoS velocity curves, now using many orders of magnitude more sources; and (vi) unveil the dynamical effect of the bar on the motions of stars in the LMC.  All these results highlight the incredible power of the Gaia astrometric mission, and in particular of its second data release.


1804.10199
Halo profiles and the concentration-mass relation for a {\Lambda}CDM Universe
Child, Habib, Heitmann, et al

Profiles of DM-dominated haloes at the group and cluster scales play an important role in modern cosmology.  Using results from 2 very large cosmo N-body sims, which increase the available volume at their mass resolution by roughly 2 orders of magnitude, robustly determine the halo concentration-mass (c-M) relation over a wide range of masses employing multiple methods of concentration measurement.  Characterize individual halo profiles as well as stacked profiles relevant for gg lensing and next-generation cluster surveys; the redshift range covered is 0<=z<=4, with a minimum halo mass of M_200c~2e11 Msun.  Despite the complexity of a proper description of a halo (environmental effects, merger history, non sphericity, relaxation state), when the mass is scaled by the nonlinear mass scale M_*(z), find that a simple non-power law form for the c-M/M_* relation provides an excellent description of the simulation results across 8 decades in M/M_* and for 0<=z<=4.  Over the mass range covered, the c-M relation has 2 asymptotic forms: an approximate power law below a mass threshold M/M_*~500-1000, transitioning to a constant value, c_0~3 at higher masses.  The relaxed halo fraction decreases with mass, transitioning to a constant value of ~0.5 above the same mass threshold.  Compare NFW and Einasto fits to stacked profiles in narrow mass bins at different redshift; expectedly, the Einasto profile provides a better description of the simulation results.  At cluster scales at low z, however, both NFW and Einasto profiles are in very good agreement with the sim results, consistent with recent WL observations.