Virial Mass Research Articles

The Mass and Redshift Dependence of Halo Star Clustering

We adopt the two-point correlation function (2PCF) as a statistical tool to quantify the spatial clustering of halo stars for galaxy systems spanning a wide range in host halo virial mass ( 11.25<log10M200c/M⊙<15 ) and redshifts (0 < z < 1.5) from the IllustrisTNG simulations. Consistent with a previous study, we identify clear correlations between the strength of the 2PCF signals and galaxy formation redshifts, but over a much wider mass range. We find that such correlations are slightly stronger at higher redshifts and get weakened with the increase of host halo mass. We demonstrate that the spatial clustering of halo stars is affected by two factors: (1) the clustering gets gradually weakened as time passes (phase mixing); (2) newly accreted stars at more recent times would increase the clustering. For more massive galaxy systems, they assemble late, and the newly accreted stars would increase the clustering. The late assembly of massive systems may also help to explain the weaker correlations between the 2PCF signals and the galaxy formation redshifts in massive halos, as their 2PCFs are affected more by recently accreted stars, while formation redshift characterizes mass accretion on a much longer timescale. We find that the orbits of satellite galaxies in more massive halos maintain larger radial anisotropy, reflecting the more active accretion state of their hosts while also contributing to their stronger mass loss rates.

Secondary halo bias through cosmic time II. Reconstructing halo properties using clustering information

When constructing mock galaxy catalogs based on suites of dark matter halo catalogs generated with approximated, calibrated, or machine-learning approaches, assigning intrinsic properties for these tracers is a step of paramount importance, given that they can shape the abundance and spatial distribution of mock galaxies and galaxy clusters. We explore the possibility of assigning properties of dark matter halos within the context of calibrated or learning approaches, explicitly using clustering information. The goal is to retrieve the correct signal of primary and secondary large-scale effective bias as a function of properties reconstructed solely based on phase-space properties of the halo distribution and dark matter density field. The algorithm reconstructs a set of halo properties (such as virial mass, maximum circular velocity, concentration, and spin) constrained to reproduce both primary and secondary (or assembly) bias. The key ingredients of the algorithm are the implementation of individually-assigned large-scale effective bias, a multi-scale approach to account for halo exclusion, and a hierarchical assignment of halo properties. The method facilitates the assignment of halo properties, aiming to replicate the large-scale effective bias, both primary and secondary. This constitutes an improvement over previous methods in the literature, especially for the high-mass end population. We have designed a strategy for reconstructing the main properties of dark matter halos obtained using calibrated or learning algorithms, such that the one- and two-point statistics (on large scales) replicate the signal from detailed $N$-body simulations. We encourage the application of this strategy (or the implementation of our algorithm) for the generation of mock catalogs of dark matter halos based on approximated methods.

Reconciling concentration to virial mass relations

The concentration--virial mass (c-M) relation is a fundamental scaling relation within the standard cold dark matter (Lambda CDM) framework well established in numerical simulations. However, observational constraints of this relation are hampered by the difficulty of characterising the properties of dark matter haloes. Recent comparisons between simulations and observations have suggested a systematic difference of the c-M relation, with higher concentrations in the latter. In this work, we undertake detailed comparisons between simulated galaxies and observations of a sample of strong-lensing galaxies. We explore several factors of the comparison with strong gravitational lensing constraints, including the choice of the generic dark matter density profile, the effect of radial resolution, the reconstruction limits of observed versus simulated mass profiles, and the role of the initial mass function in the derivation of the dark matter parameters. Furthermore, we show the dependence of the c-M relation on reconstruction and model errors through a detailed comparison of real and simulated gravitational lensing systems. An effective reconciliation of simulated and observed c-M relations can be achieved if one considers less strict assumptions on the dark matter profile, for example, by changing the slope of a generic NFW profile or focusing on rather extreme combinations of stellar-to-dark matter distributions. A minor effect is inherent to the applied method: fits to the NFW profile on a less well-constrained inner mass profile yield slightly higher concentrations and lower virial masses.

Constrained cosmological simulations of the Local Group using Bayesian hierarchical field-level inference

We present a novel approach based on Bayesian field-level inference that provides representative initial conditions for simulation of the Local Group (LG) of galaxies and its neighbourhood, constrained by present-day observations. We extended the Bayesian Origin Reconstruction from Galaxies ( algorithm with a multi-resolution approach, allowing us to reach the smaller scales needed to apply the constraints. Our data model simultaneously accounts for observations of mass tracers within the dark haloes of the Milky Way (MW) and M31, for their observed separation and relative velocity, and for the quiet surrounding Hubble flow, represented by the positions and velocities of 31 galaxies at distances between one and four megaparsec. Our approach delivers representative posterior samples of realisations that are statistically and simultaneously consistent with all of these observations, leading to significantly tighter mass constraints than found if the individual datasets are considered separately. In particular, we estimate the virial masses of the MW and M31 to be $ (M_ 200c /M_ and $12.33 respectively, their sum to be $ 200c /M_ and the enclosed mass within spheres of radius $R$ to be $ (M(R)/M_ and $12.96 for $R=1$ Mpc and $3$ Mpc, respectively. The M31-MW orbit is nearly radial for most of our realisations, and most of them feature a dark matter sheet aligning approximately with the supergalactic plane, despite the surrounding density field not being used explicitly as a constraint. High-resolution, high-fidelity resimulations from initial conditions identified using the approximate simulations of our inference scheme continue to satisfy the observational constraints, demonstrating a route to future high-resolution, full-physics simulations of ensembles of LG look-alikes, all of which closely mirror the observed properties of the real system and its immediate environment.

WIYN Open Cluster Study. XC. Radial-velocity Measurements and Spectroscopic Binary Orbits in the Open Cluster NGC 2506

NGC 2506 is a rich, intermediate-age (2.0 Gyr), metal-poor ([Fe/H] ∼ −0.2) open cluster. This work presents the results of 12,157 spectroscopic radial-velocity measurements of 2442 stars in the NGC 2506 field obtained over 41 yr, made as part of the WIYN Open Cluster Study. Radial-velocity measurements are complete for the population of proper-motion member stars brighter than a Gaia G magnitude of 15.5, in which 320 proper-motion and radial-velocity cluster members were identified. Within the observation limit of G < 16.5, 469 proper-motion and radial-velocity members were identified. This work reports on the characteristics of NGC 2506, including projected spatial distribution, radial-velocity dispersion, and virial mass. This work also presents orbital solutions for 49 binary members with periods between 1 and 7580 days. NGC 2506 has an incompleteness-corrected binary frequency for binaries with periods less than 104 days of 35% ± 5%. This work also discusses in detail the 14 blue stragglers stars of NGC 2506—finding at least 64% ± 21% to be in binaries, five yellow straggler stars, and several other stars of note.

Uncovering the first-infall history of the LMC through its dynamical impact in the Milky Way halo

ABSTRACT The gravitational interactions between the LMC and the Milky Way cause dynamical perturbations in the MW halo, leading to biased distributions of stellar density and kinematics. We run 50 high-resolution N-body simulations exploring varying masses and halo shapes of the MW and LMC to study the evolution of LMC-induced perturbations. By measuring mean velocities of simulated halo stars, we identify a discontinuity between the first-infall and second-passage scenarios of the LMC’s orbital history. In the first-infall, the Galactocentric latitudinal velocity hovers around 16 km s$^{-1}$ for stars at 50–100 kpc, while it subsides to about 8 km s$^{-1}$ in the second-passage scenario. We demonstrate that, this reduced perturbation magnitude in the second-passage scenario is mainly due to the short dynamical times of the Galactic inner halo and the lower velocity of the LMC during its second infall into the MW. Using a subset of $\sim 1100$ RR Lyrae stars located in the outer halo (50 kpc $\le R_{\mathrm{GC}}\lt $ 100 kpc) with precise distance estimates from Gaia, we find the mean latitudinal velocity ($v_{b}$) in the Galactocentric frame to be $\langle v_{b} \rangle =18.1 \pm 4.1$ km s$^{-1}$. The observation supports the first-infall scenario with a massive LMC ($\sim$$2.1 \times 10^{11} \, \mathrm{M}_{\odot }$) at infall, an oblate MW halo with a virial mass $M_{200}\lt 1.4\times 10^{12}\,\mathrm{M}_{\odot }$ and a flattening parameter $q\gt 0.7$. Our study indicates that LMC-induced kinematic disturbances can reveal its orbital history and key characteristics, as well as those of the MW. This approach shows promise in helping determine fundamental parameters of both galaxies.

Stripe 82X Data Release 3: Multiwavelength Catalog with New Spectroscopic Redshifts and Black Hole Masses

We present the third catalog release of the wide-area (31.3 deg2) Stripe 82 X-ray survey. This catalog combines previously published X-ray source properties with multiwavelength counterparts and photometric redshifts, presents 343 new spectroscopic redshifts, and provides black hole masses for 1297 Type 1 active galactic nuclei (AGN). With spectroscopic redshifts for 3457 out of 6181 Stripe 82X sources, the survey has a spectroscopic completeness of 56%. This completeness rises to 90% when considering the contiguous portions of the Stripe 82X survey with homogeneous X-ray coverage at an optical magnitude limit of r < 22. Within that portion of the survey, 23% of AGN can be considered obscured by being either a Type 2 AGN, reddened (R − K > 4, Vega), or X-ray obscured with a column density of N H > 1022 cm−2. Unlike other surveys, there is only an 18% overlap between Type 2 and X-ray obscured AGN. We calculated black hole masses for Type 1 AGN that have Sloan Digital Sky Survey spectra using virial mass estimators calibrated on the Hβ, Mg ii, Hα, and C iv emission lines. We find wide scatter in these black hole mass estimates, indicating that statistical analyses should use black hole masses calculated from the same formula to minimize bias. We find that the AGN with the highest X-ray luminosities are accreting at the highest Eddington ratios, consistent with the picture that most black hole mass accretion happens in the phase when the AGN is luminous (L 2−10keV > 1045 erg s−1).

Sunyaev–Zeldovich Signals from L* Galaxies: Observations, Analytics, and Simulations

We analyze measurements of the thermal Sunyaev–Zeldovich (tSZ) effect arising in the circumgalactic medium (CGM) of L* galaxies, reported by J. N. Bregman et al. (B+22) and S. Das et al. (D+23). In our analysis, we use the Y. Faerman et al. CGM models, a new power-law model (PLM), and the TNG100 simulation. For a given M vir, our PLM has four parameters: the fraction, f hCGM, of the halo baryon mass in hot CGM gas, the ratio, ϕ T , of the actual gas temperature at the virial radius to the virial temperature, and the power-law indices, a P,th and a n for the thermal electron pressure and the hydrogen nucleon density. The B+22 Compton-y profile implies steep electron pressure slopes (a P,th ≃ 2). For isothermal conditions, the temperature is at least 1.1 × 106 K, with a hot CGM gas mass of up to 3.5 × 1011 M ⊙ for a virial mass of 2.75 × 1012 M ⊙. However, if isothermal, the gas must be expanding out of the halos. An isentropic equation of state is favored for which hydrostatic equilibrium is possible. The B+22 and D+23 results are consistent with each other and with recent (0.5–2 keV) CGM X-ray observations of Milky Way mass systems. For M vir ≃ 3 × 1012 M ⊙, the scaled Compton pressure integrals, E(z)−2/3Y500/Mvir,125/3 , lie in the narrow range, 2.5 × 10−4–5.0 × 10−4 kpc2, for all three sets of observations. TNG100 underpredicts the tSZ parameters by factors ∼0.5 dex for the L* galaxies, suggesting that the feedback strengths and CGM gas losses are overestimated in the simulated halos at these mass scales.

AXES-2MRS: A new all-sky catalogue of extended X-ray galaxy groups

Context. Understanding baryonic physics at the galaxy-group level is a prerequisite for cosmological studies of the large-scale structure. One poorly understood aspect of galaxy groups is related to the properties of their hot intragroup medium. The well-studied X-ray groups have strong cool cores by which they were selected, so expanding the selection of groups is currently an important avenue in uncovering the diversity within the galaxy group population. Aims. We present a new all-sky catalogue of X-ray-detected groups (AXES-2MRS) based on the identification of large X-ray sources found in the ROSAT All-Sky Survey (RASS) with the Two Micron Redshift Survey (2MRS) Bayesian Group Catalogue. We studied the basic properties of these galaxy groups to gain insights into the effect of different group selections on the properties. Methods. In addition to X-ray luminosity from shallow survey data of RASS, we obtained detailed X-ray properties of the groups by matching the AXES-2MRS catalogue to archival X-ray observations by XMM-Newton and complemented this by adding the published XMM-Newton results on galaxy clusters in our catalogue. We analysed temperature and density to the lowest overdensity accessible by the data, obtaining hydrostatic mass estimates at a uniform overdensity of 10 000 times the critical, M10 000, and comparing them to the velocity dispersions of the groups. We explored the relationship between X-ray and optical properties of AXES-2MRS groups through the σv−LX, σv−kT, kT−LX, σv−M, and c200−LX scaling relations. Results. We find a large spread in the central mass ( M10 000), measured by XMM-Newton, to virial mass (M200), inferred by the velocity dispersion, ratios for galaxy groups. This can either indicate that large non-thermal pressure of galaxy groups affects our X-ray mass measurements or the effect of a diversity of halo concentrations on the X-ray properties of galaxy groups. Previous catalogues based on detecting the peak of the X-ray emission preferentially sample the high-concentration groups. In contrast, our new catalogue uncovered many low-concentration groups, completely revising our understanding of X-ray groups.

Inferring the Mass Content of Galaxy Clusters with Satellite Kinematics and Jeans Anisotropic Modeling

Satellite galaxies can be used to indicate the dynamic mass of galaxy groups and clusters. In this study, we apply the axisymmetric Jeans Anisotropic Multi-Gaussian Expansion (JAM) modeling to satellite galaxies in 28 galaxy clusters selected from the TNG300-1 simulation with halo masses of log10M200/M⊙>14.3 . If using true bound satellites as tracers, the best constrained total mass within the half-mass radius of satellites, M(<r half), and the virial mass, M 200, have average biases of −0.01 and 0.03 dex, with average scatters of 0.11 dex and 0.15 dex. If selecting companions in the redshift space with a line-of-sight depth of 2000 km s−1, the biases are −0.06 and 0.01 dex, while the scatters are 0.12 and 0.18 dex for M(<r half) and M 200. By comparing the best-fitting and actual density profiles, we find that ∼29% of the best-fitting density profiles show very good agreement with the truth, ∼32% display over/underestimates at most of the radial range with biased M(<r half), and 39% show under/overestimates in central regions and over/underestimates in the outskirts, with good constraints on M(<r half); yet most of the best constraints are still consistent with the true profiles within 1σ statistical uncertainties for the three circumstances. Using a mock DESI Bright Galaxy Survey catalog with the effect of fiber incompleteness, we find DESI fiber assignments and the choice of flux limits barely modify the velocity dispersion profiles and are thus unlikely to affect the dynamical modeling outcomes. Our results show that with current and future deep spectroscopic surveys, JAM can be a powerful tool to constrain the underlying density profiles of individual massive galaxy clusters.

Rest-frame Optical Spectroscopy of Ten z ∼ 2 Weak Emission-line Quasars

We present near-infrared spectroscopy of 10 weak emission-line quasars (WLQs) at redshifts of z ∼ 2, obtained with the Palomar 200 inch Hale Telescope. WLQs are an exceptional population of type 1 quasars that exhibit weak or no broad emission lines in the ultraviolet (e.g., the C iv λ1549 line), and they display remarkable X-ray properties. We derive Hβ-based single-epoch virial black hole masses (median value 1.7 × 109 M ⊙) and Eddington ratios (median value 0.5) for our sources. We confirm the previous finding that WLQ Hβ lines, as a major low-ionization line, are not significantly weak compared to typical quasars. The most prominent feature of the WLQ optical spectra is the universally weak/absent [O iii] λ5007 emission. They also display stronger optical Fe ii emission than typical quasars. Our results favor the super-Eddington accretion scenario for WLQs, where the weak lines are a result of a soft ionizing continuum; the geometrically thick inner accretion disk and/or its associated outflow is responsible for obscuring the nuclear high-energy radiation and producing the soft ionizing continuum. We also report candidate extreme [O iii] outflows (blueshifts of ≈500 and 4900 km s−1) in one object.

From Halos to Galaxies. IX. Estimate of Halo Assembly History for SDSS Galaxy Groups

The properties of the galaxies are tightly connected to their host halo mass and halo assembly history. Accurate measurement of the halo assembly history in observation is challenging but crucial to the understanding of galaxy formation and evolution. The stellar-to-halo mass ratio (M */M h) for the centrals has often been used to indicate the halo assembly time t h,50 of the group, where t h,50 is the lookback time at which a halo has assembled half of its present-day virial mass. Using mock data from the semi-analytic models, we find that M */M h shows a significant scatter with t h,50, with a strong systematic difference between the group with a star-forming central (blue group) and passive central (red group). To improve the accuracy, we develop machine learning models to estimate t h,50 for galaxy groups using only observable quantities in the mocks. Since star formation quenching will decouple the co-growth of the dark matter and baryon, we train our models separately for blue and red groups. Our models have successfully recovered t h,50, within an accuracy of ∼1.09 Gyr. With careful calibrations of individual observable quantities in the mocks with Sloan Digital Sky Survey (SDSS) observations, we apply the trained models to the SDSS Yang et al. groups and derive the t h,50 for each group for the first time. The derived SDSS t h,50 distributions are in good agreement with that in the mocks, in particular for blue groups. The derived halo assembly history, together with the halo mass, make an important step forward in studying the halo–galaxy connections in observation.

DAVOS: Dwarf Active Galactic Nuclei from Variability for the Origins of Seeds: Properties of Variability-selected Active Galactic Nuclei in the COSMOS Field and Expectations for the Rubin Observatory

We study the black hole mass–host galaxy stellar mass relation, M BH–M *, of a sample of z < 4 optically variable active galactic nuclei (AGNs) in the COSMOS field. The parent sample of 491 COSMOS AGNs were identified by optical variability from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) program. Using publicly available catalogs and spectra, we consolidate their spectroscopic redshifts and estimate virial black hole masses using broad-line widths and luminosities. We show that variability searches with deep, high-precision photometry like the HSC-SSP can identity AGNs in low-mass galaxies up to z ∼ 1. However, their black holes are more massive given their host galaxy stellar masses than predicted by the local relation for active galaxies. We report that z ∼ 0.5–4 variability-selected AGNs are meanwhile more consistent with the M BH–M * relation for local inactive early-type galaxies. This result is in agreement with most previous studies of the M BH–M * relation at similar redshifts and indicates that AGNs selected from variability are not intrinsically different from the broad-line Type 1 AGN population at similar luminosities. Our results demonstrate the need for robust black hole and stellar mass estimates for intermediate-mass black hole candidates in low-mass galaxies at similar redshifts to anchor this scaling relation. Assuming that these results do not reflect a selection bias, they appear to be consistent with self-regulated feedback models wherein the central black hole and stars in galaxies grow in tandem.

A normal broad line AGN SDSS J1617+0638 as the host galaxy of a central tidal disruption event

ABSTRACT In this manuscript, strong clues are reported to support the normal broad line AGN SDSS J1617+0638 as the host galaxy harbouring a central tidal disruption event (TDE). Through the optical flare in the CSS 8.5yr-long light curve and the none-variability in the up-to-date ASAS-SN light curves, the theoretical TDE model described by the mosfit code can be applied in SDSS J1617+0638. Meanwhile, considering the assumed central TDE expected continuum emissions not strong enough to describe the continuum emissions in the SDSS spectrum of SDSS J1617+0638, an additional power-law component from pre-existing AGN activity should be necessary in SDSS J1617+0638. Furthermore, considering the short time duration to the observed date for the SDSS spectrum from the starting time of the assumed central TDE in SDSS J1617+0638, TDE model expected accreting mass only about 0.03 $\mathrm{ M}_\odot$ can lead to few effects of TDEs debris on the observed broad emission lines in the SDSS spectrum of SDSS J1617+0638, indicating the TDE model determined BH mass simply consistent with the virial BH mass by broad emission lines, as determined results in SDSS J1617+0638. Therefore, through both the photometric variability and the spectroscopic results, a central TDE can be preferred in the normal broad line AGN SDSS J1617+0638 with pre-existing central AGN activity and pre-existing broad emission line regions.

Milky Way-est: Cosmological Zoom-in Simulations with Large Magellanic Cloud and Gaia–Sausage–Enceladus Analogs

We present Milky Way-est, a suite of 20 cosmological cold-dark-matter-only zoom-in simulations of Milky Way (MW)-like host halos. Milky Way-est hosts are selected such that they (i) are consistent with the MW’s measured halo mass and concentration, (ii) accrete a Large Magellanic Cloud (LMC)-like (≈1011 M ⊙) subhalo within the last 2 Gyr on a realistic orbit, placing them near 50 kpc from the host center at z ≈ 0, and (iii) undergo a >1:5 sub-to-host halo mass ratio merger with a Gaia–Sausage–Enceladus (GSE)-like system at early times (0.67 < z < 3). Hosts satisfying these LMC and GSE constraints constitute <1% of all halos in the MW’s mass range, and their total masses grow rapidly at late times due to LMC analog accretion. Compared to hosts of a similar final halo mass that are not selected to include LMC and GSE analogs, Milky Way-est hosts contain 22% more subhalos with present-day virial masses above 108 M ⊙ throughout the virial radius, on average. This enhancement reaches ≈80% in the inner 100 kpc and is largely, if not entirely, due to LMC-associated subhalos. These systems also induce spatial anisotropy in Milky Way-est subhalo populations, with ≈60% of the total subhalo population within 100 kpc found in the current direction of the LMC. Meanwhile, we find that GSE-associated subhalos do not significantly contribute to present-day Milky Way-est subhalo populations. These results provide context for our Galaxy’s dark matter structure and subhalo population and will help interpret a range of measurements that are currently only possible in the MW.

X-Ray View of Little Red Dots: Do They Host Supermassive Black Holes?

The discovery of Little Red Dots (LRDs)—a population of compact, high-redshift, dust-reddened galaxies—is one of the most surprising results from JWST. However, the nature of LRDs is still debated: does the near-infrared emission originate from accreting supermassive black holes (SMBHs), or intense star formation? In this work, we utilize ultra-deep Chandra observations and study LRDs residing behind the lensing galaxy cluster, A2744. We probe the X-ray emission from individual galaxies but find that they remain undetected and provide SMBH mass upper limits of ≲(1.5–16) × 106 M ⊙ assuming Eddington limited accretion. To increase the signal-to-noise ratios, we conduct a stacking analysis of the full sample with a total lensed exposure time of ≈87 Ms. We also bin the galaxies based on their stellar mass, lensing magnification, and detected broad-line Hα emission. For the LRDs exhibiting broad-line Hα emission, there is a hint of a stacked signal (∼2.6σ), corresponding to an SMBH mass of ∼3.2 × 106 M ⊙. Assuming unobscured, Eddington-limited accretion, this black hole (BH) mass is at least 1.5 orders of magnitude lower than that inferred from virial mass estimates using JWST spectra. Given galaxy-dominated stellar mass estimates, our results imply that LRDs do not host overmassive SMBHs and/or accrete at a few percent of their Eddington limit. However, alternative stellar mass estimates may still support that LRDs host overmassive BHs. The significant discrepancy between the JWST and Chandra data hints that the scaling relations used to infer the SMBH mass from the Hα line and virial relations may not be applicable for high-redshift LRDs.

Scalar field dark matter: impact of supernova-driven blowouts on the soliton structure of low-mass dark matter haloes

ABSTRACT We present the first study on the gravitational impact of supernova feedback in an isolated soliton and a spherically symmetric dwarf scalar field dark matter (SFDM) halo of virial mass $1\times 10^{10}\,\mathrm{M_\odot }$. We use a boson mass $m=10^{-22}\,\mathrm{eV\,c^{-2}}$ and a soliton core $r_\mathrm{ c} \approx 0.7$ kpc, comparable to typical half-light radii of Local Group dwarf galaxies. We simulate the rapid gas removal from the centre of the soliton by a concentric external time-dependent Hernquist potential. We explore two scenarios of feedback blowouts: (i) a massive single burst and (ii) multiple consecutive blowouts injecting the same total energy to the system, including various magnitudes for the blowouts in both scenarios. In all cases, we find one single blowout has a stronger effect on reducing the soliton central density. Feedback leads to central soliton densities that oscillate quasi-periodically for an isolated soliton and stochastically for an SFDM halo. The range in the density amplitude depends on the strength of the blowout; however, we observe typical variations of a factor of $\geqslant$2. One important consequence of the stochastic fluctuating densities is that, if we had no prior knowledge of the system evolution, we can only know the configuration profile at a specific time within some accuracy. By fitting soliton profiles at different times to our simulated structures, we found the (1$\sigma$) scatter of their time-dependent density profiles. For configurations within the 1$\sigma$ range, we find the inferred boson mass is typically less than 20 per cent different from the real value used in our simulations. Finally, we compare the observed dynamical masses of field dwarf galaxies in our Local Group with the implied range of viable solitons from our simulations and find good agreement.

Effect of the Large Magellanic Cloud on the kinematics of Milky Way satellites and virial mass estimate

We present a study illustrating the effects of the passage of a Large Magellanic Cloud (LMC) mass satellite on the distance and velocity distributions of satellites in Λ+Cold Dark Matter simulations of Milky Way (MW) sized halos. In agreement with previous studies, we find that during such a passage the velocity distribution develops a high-velocity tail, which can bias velocity-based virial halo mass estimates. When the velocity distribution of MW satellites is corrected for effects of the LMC passage, it is consistent with the distributions in halos of masses as low as and as high as 1.5×1012M⊙. We present a new halo mass estimator , where c is the coefficient calibrated using satellite systems in the simulated MW-sized halos, is the variance of 3D velocities taken with the sign of the radial velocity of each satellite, and is the median halocentric distance of the satellites. We show that the estimator has only s=8% scatter around the median relation of the estimated and true halo masses and deviates by &lt;2s from the median during the pericentric passage of an LMC-like subhalo. This is because and deviate in the opposite directions during such passages. We apply the estimator to the MW satellite system and estimate the virial mass of the Milky Way of , in good agreement with several recent estimates using other methods.

The SRG/eROSITA All-Sky Survey. View of the Virgo Cluster

As the closest galaxy cluster, the Virgo Cluster is an exemplary environment for the study of the large-scale filamentary structure and physical effects that are present in cluster outskirts but absent from the more easily studied inner regions. Here, we present an analysis of the SRG/eROSITA data from five all-sky surveys. eROSITA allows us to resolve the entire Virgo cluster and its outskirts on scales between 1 kpc and 3 Mpc, covering a total area on the sky of about 25$^ by 25$^ We utilized image manipulation techniques and surface brightness profiles to search for extended emission, surface brightness edges, and features in the outskirts. We employed a method of comparing mean and median profiles to measure gas clumping out to and beyond the virial radius. Surface brightness analysis of the cluster and individual sectors of the cluster reveal the full extent of previously identified cold fronts to the north and south. The emissivity bias due to gas clumping, which we quantify over three orders of magnitude in the radial range, is found to be mild, consistent with previous findings. We find uniform clumping measurements in all directions, with no enhancements along candidate filaments. We find an estimated virial gas mass of $M_ gas r&lt;r_ $\,M$_ Through imaging analysis we detect the presence of extended emission spanning 320\,kpc to the southwest of M49. The extension has a significance of 3.15sigma and is coincident with radio emission detected with LOFAR, which could be evidence of an accretion shock or turbulent reacceleration as the M49 group or background W' cloud falls into the cluster and interacts with the intracluster medium.

Improving the accuracy of halo mass based statistics for fast approximate N-body simulations

ABSTRACT Approximate N-body methods, such as fastpm and cola, have been successful in modelling halo and galaxy clustering statistics, but their low resolution on small scales is a limitation for applications that require high precision. Full N-body simulations can provide better accuracy but are too computationally expensive for a quick exploration of cosmological parameters. This paper presents a method for correcting distinct haloes identified in fast N-body simulations, so that various halo statistics improve to a percent level accuracy. The scheme seeks to find empirical corrections to halo properties such that the virial mass is the same as that of a corresponding halo in a full N-body simulation. The modified outer density contour of the corrected halo is determined on the basis of the fastpm settings and the number of particles inside the halo. This method only changes some parameters of the halo finder, and does not require any extra CPU-cost. We demonstrate that the adjusted halo catalogues of fastpm simulations significantly improve the precision of halo mass-based statistics from redshifts $z=0.0$ to 1.0, and that our calibration can be applied to different cosmologies without needing to be recalibrated.