scholarly journals Halo-model Analysis of the Clustering of Photometric Luminous Red Galaxies at 0.10 ≤ z ≤1.05 from the Subaru Hyper Suprime-Cam Survey

2021 ◽  
Vol 922 (1) ◽  
pp. 23
Author(s):  
Shogo Ishikawa ◽  
Teppei Okumura ◽  
Masamune Oguri ◽  
Sheng-Chieh Lin
Keyword(s):  
Large Fraction ◽  
Critical Mass ◽  
Stellar Mass ◽  
Distribution Analysis ◽  
Dark Halo ◽  
Mass Dependence ◽  
Luminous Red Galaxies ◽  
Order Of Magnitude ◽  
Stellar Masses ◽  
Red Galaxies

Abstract We present the clustering analysis of photometric luminous red galaxies (LRGs) at a redshift range of 0.1 ≤ z ≤ 1.05 using 615,317 photometric LRGs selected from the Hyper Suprime-Cam Subaru Strategic Program, covering ∼124 deg2. Our sample covers a broad range of stellar masses and photometric redshifts and enables a halo occupation distribution analysis to study the redshift and stellar-mass dependence of dark halo properties of LRGs. We find a tight correlation between the characteristic dark halo mass to host central LRGs, M min , and the number density of LRGs, independently of redshifts, indicating that the formation of LRGs is associated with the global environment. The M min of LRGs depends only weakly on the stellar mass M ⋆ at M ⋆ ≲ 1010.75 h −2 M ⊙ at 0.3 < z < 1.05, in contrast to the case for all photometrically selected galaxies, for which M min shows significant dependence on M ⋆ even at low M ⋆. The weak stellar-mass dependence is indicative of the dark halo mass being the key parameter for the formation of LRGs, rather than the stellar mass. Our result suggests that the halo mass of ∼1012.5±0.2 h −1 M ⊙ is the critical mass for an efficient halo quenching due to the halo environment. We compare our result with the result of the hydrodynamical simulation to find that low-mass LRGs at z ∼ 1 will increase their stellar masses by an order of magnitude from z = 1 to 0 through mergers and satellite accretions, and that a large fraction of massive LRGs at z < 0.9 consist of LRGs that recently migrated from massive green valley galaxies or those that evolved from less massive LRGs through mergers and satellite accretions.

scholarly journals The Slow Growth of Massive Galaxies in Rapidly Growing Dark Matter Halos

2009 ◽  
Vol 5 (S262) ◽  
pp. 244-247
Author(s):  
Michael J. I. Brown ◽  
Keyword(s):  
Dark Matter ◽  
Rapid Growth ◽  
Observational Studies ◽  
Cold Dark Matter ◽  
Slow Growth ◽  
Stellar Mass ◽  
Dark Matter Halos ◽  
Massive Galaxies ◽  
Stellar Masses ◽  
Red Galaxies

AbstractIn cold dark matter cosmologies, the most massive dark matter halos are predicted to undergo rapid growth at z < 1. While there is the expectation that massive galaxies will also rapidly grow via merging, recent observational studies conclude that the stellar masses of the most massive galaxies grow by just ~ 30% at z < 1. We have used the observed space density and clustering of z < 1 red galaxies in Boötes to determine how these galaxies populate dark matter halos. In the most massive dark matter halos, central galaxy stellar mass is proportional to halo mass to the power of a ~1/3 and much of the stellar mass resides within satellite galaxies. As a consequence, the most massive galaxies grow slowly even though they reside within rapidly growing dark matter halos.

scholarly journals Exploring the luminosity evolution and stellar mass assembly of 2SLAQ luminous red galaxies between redshifts 0.4 and 0.8

2010 ◽  
Vol 402 (4) ◽  
pp. 2264-2278 ◽  
Author(s):  
Manda Banerji ◽  
Ignacio Ferreras ◽  
Filipe B. Abdalla ◽  
Paul Hewett ◽  
Ofer Lahav
Keyword(s):  
Stellar Mass ◽  
Luminous Red Galaxies ◽  
Mass Assembly ◽  
Red Galaxies ◽  
Luminosity Evolution

scholarly journals Weighing Milky Way satellites with LISA

2021 ◽  
Vol 502 (1) ◽  
pp. L55-L60
Author(s):  
Valeriya Korol ◽  
Vasily Belokurov ◽  
Christopher J Moore ◽  
Silvia Toonen
Keyword(s):  
Gravitational Waves ◽  
White Dwarf ◽  
Milky Way ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Star Formation History ◽  
Population Synthesis ◽  
White Dwarf Stars ◽  
Order Of Magnitude ◽  
Stellar Masses

ABSTRACT White dwarf stars are a well-established tool for studying Galactic stellar populations. Two white dwarfs in a tight binary system offer us an additional messenger – gravitational waves – for exploring the Milky Way and its immediate surroundings. Gravitational waves produced by double white dwarf (DWD) binaries can be detected by the future Laser Interferometer Space Antenna (LISA). Numerous and widespread DWDs have the potential to probe shapes, masses, and formation histories of the stellar populations in the Galactic neighbourhood. In this work we outline a method for estimating the total stellar mass of Milky Way satellite galaxies based on the number of DWDs detected by LISA. To constrain the mass we perform a Bayesian inference using binary population synthesis models and considering the number of detected DWDs associated with the satellite and the measured distance to the satellite as the only inputs. Based on a fiducial binary population synthesis model we find that for large satellites the stellar masses can be recovered to within (1) a factor 2 if the star formation history (SFH) is known and (2) an order of magnitude when marginalizing over different SFH models. For smaller satellites we can place upper limits on their stellar mass. Gravitational wave observations can provide mass measurements for large satellites that are comparable, and in some cases more precise, than standard electromagnetic observations.

scholarly journals Towards a consistent framework of comparing galaxy mergers in observations and simulations

2020 ◽  
Vol 644 ◽  
pp. A87
Author(s):  
L. Wang ◽  
W. J. Pearson ◽  
V. Rodriguez-Gomez
Keyword(s):  
Mass Range ◽  
Stellar Mass ◽  
Mass Scale ◽  
Mass Dependence ◽  
Deep Convolutional Neural Networks ◽  
Wide Range ◽  
The Galaxy ◽  
Major Merger ◽  
Mass Assembly ◽  
Stellar Masses

Aims. We aim to perform consistent comparisons between observations and simulations on the mass dependence of the galaxy major merger fraction at low redshift over an unprecedentedly wide range of stellar masses (∼109 to 1012 M⊙). Methods. We first carry out forward modelling of ideal synthetic images of major mergers and non-mergers selected from the Next Generation Illustris Simulations (IllustrisTNG) to include major observational effects. We then train deep convolutional neural networks (CNNs) using realistic mock observations of galaxy samples from the simulations. Subsequently, we apply the trained CNNs to real the Kilo-Degree Survey (KiDS) images of galaxies selected from the Galaxy And Mass Assembly (GAMA) survey. Based on the major merger samples, which are detected in a consistent manner in the observations and simulations, we determine the dependence of major merger fraction on stellar mass at z ∼ 0.15 and make comparisons between the two. Results. The detected major merger fraction in the GAMA/KiDS observations has a fairly mild decreasing trend with increasing stellar mass over the mass range 109 M⊙ <  M* <  1011.5 M⊙. There is good agreement in the mass dependence of the major merger fraction in the GAMA/KiDS observations and the IllustrisTNG simulations over 109.5 M⊙ <  M* <  1010.5 M⊙. However, the observations and the simulations show some differences at M* >  1010.5 M⊙, possibly due to the supermassive blackhole feedback in its low-accretion state in the simulations which causes a sharp transition in the quenched fractions at this mass scale. The discrepancy could also be due to the relatively small volume of the simulations and/or differences in how stellar masses are measured in simulations and observations.

scholarly journals Environmental Effects on LRGs as Cosmic Chronometers

2015 ◽  
Vol 11 (S319) ◽  
pp. 140-140
Author(s):  
Gaochao Liu ◽  
Youjun Lu ◽  
Lizhi Xie ◽  
Xuelei Chen ◽  
Yongheng Zhao
Keyword(s):  
Star Formation ◽  
Age Distribution ◽  
Hubble Constant ◽  
Star Formation History ◽  
Mass Dependence ◽  
Population Synthesis ◽  
Luminous Red Galaxies ◽  
Formation History ◽  
The Mean ◽  
Red Galaxies

AbstractMassive luminous red galaxies (LRGs) are believed to be evolving passively and can be used as cosmic chronometers to estimate the Hubble constant (the differential age method). However, different LRGs may be located in different environments. We investigate the environmental and mass dependence of the formation of ‘quiescent’ LRGs by using the population synthesis software STARLIGHT. We derive the stellar populations in each LRG, and obtain the mean age distribution and the mean star formation history (SFH) of those LRGs. We find that there is no apparent dependence of the mean age and the SFH of quiescent LRGs on their environment, while the ages of these quiescent LRGs depend weakly on their mass. We also evaluate the possible uncertainties in estimating the Hubble constant by the differential age method when using LRGs as cosmic chronometers.

scholarly journals Bright galaxy sample in the Kilo-Degree Survey Data Release 4

2021 ◽  
Vol 653 ◽  
pp. A82
Author(s):  
M. Bilicki ◽  
A. Dvornik ◽  
H. Hoekstra ◽  
A. H. Wright ◽  
N. E. Chisari ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Stellar Mass ◽  
Supervised Machine Learning ◽  
Bright Galaxy ◽  
Absolute Deviation ◽  
Data Release ◽  
Blue Galaxies ◽  
Galaxy Sample ◽  
Stellar Masses ◽  
Red Galaxies

We present a bright galaxy sample with accurate and precise photometric redshifts (photo-zs), selected using ugriZYJHKs photometry from the Kilo-Degree Survey (KiDS) Data Release 4. The highly pure and complete dataset is flux-limited at r < 20 mag, covers ∼1000 deg2, and contains about 1 million galaxies after artifact masking. We exploit the overlap with Galaxy And Mass Assembly spectroscopy as calibration to determine photo-zs with the supervised machine learning neural network algorithm implemented in the ANNz2 software. The photo-zs have a mean error of |⟨δz⟩|∼5 × 10−4 and low scatter (scaled mean absolute deviation of ∼0.018(1 + z)); they are both practically independent of the r-band magnitude and photo-z at 0.05 < zphot < 0.5. Combined with the 9-band photometry, these allow us to estimate robust absolute magnitudes and stellar masses for the full sample. As a demonstration of the usefulness of these data, we split the dataset into red and blue galaxies, used them as lenses, and measured the weak gravitational lensing signal around them for five stellar mass bins. We fit a halo model to these high-precision measurements to constrain the stellar-mass–halo-mass relations for blue and red galaxies. We find that for high stellar mass (M⋆ > 5 × 1011 M⊙), the red galaxies occupy dark matter halos that are much more massive than those occupied by blue galaxies with the same stellar mass.

scholarly journals A mass threshold for galactic gas discs by spin flips

2020 ◽  
Vol 493 (3) ◽  
pp. 4126-4142 ◽  
Author(s):  
Avishai Dekel ◽  
Omri Ginzburg ◽  
Fangzhou Jiang ◽  
Jonathan Freundlich ◽  
Sharon Lapiner ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Critical Mass ◽  
Stellar Mass ◽  
Mass Dependence ◽  
Mass Ratio ◽  
High Angular Momentum ◽  
Merger Rate ◽  
Spin Flips ◽  
Supernova Feedback ◽  
Gas Supply

ABSTRACT We predict, analytically and by simulations, that gas discs tend to survive only in haloes above a threshold mass ∼2 × 1011 M⊙ (stellar mass ∼109 M⊙), with only a weak redshift dependence. At lower masses, the disc spins typically flip in less than an orbital time due to mergers associated with a change in the pattern of the feeding cosmic-web streams. This threshold arises from the halo merger rate when accounting for the mass dependence of the ratio of galactic baryons and halo mass. Above the threshold, wet compactions lead to massive central nuggets that allow the longevity of extended clumpy gas rings. Supernova feedback has a major role in disrupting discs below the critical mass, by driving the stellar-to-halo mass ratio that affects the merger rate, by stirring up turbulence and suppressing high-angular-momentum gas supply, and by confining major compactions to the critical mass. Our predictions seem consistent with current observed fractions of gas discs, to be explored by future observations that will resolve galaxies below 109 M⊙ at high redshifts, e.g. by JWST.

scholarly journals Mask-Ematics: Modeling the Effects of Masks in COVID-19 Transmission in High-Risk Environments

Epidemiologia ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 207-226
Author(s):  
Anthony Morciglio ◽  
Bin Zhang ◽  
Gerardo Chowell ◽  
James M. Hyman ◽  
Yi Jiang
Keyword(s):  
Public Health ◽  
High Risk ◽  
Disease Transmission ◽  
Large Fraction ◽  
Critical Mass ◽  
Transmission Model ◽  
Reproductive Number ◽  
High Quality ◽  
Moderate Quality ◽  
Epidemic Size

The COVID-19 pandemic has placed an unprecedented burden on public health and strained the worldwide economy. The rapid spread of COVID-19 has been predominantly driven by aerosol transmission, and scientific research supports the use of face masks to reduce transmission. However, a systematic and quantitative understanding of how face masks reduce disease transmission is still lacking. We used epidemic data from the Diamond Princess cruise ship to calibrate a transmission model in a high-risk setting and derive the reproductive number for the model. We explain how the terms in the reproductive number reflect the contributions of the different infectious states to the spread of the infection. We used that model to compare the infection spread within a homogeneously mixed population for different types of masks, the timing of mask policy, and compliance of wearing masks. Our results suggest substantial reductions in epidemic size and mortality rate provided by at least 75% of people wearing masks (robust for different mask types). We also evaluated the timing of the mask implementation. We illustrate how ample compliance with moderate-quality masks at the start of an epidemic attained similar mortality reductions to less compliance and the use of high-quality masks after the epidemic took off. We observed that a critical mass of 84% of the population wearing masks can completely stop the spread of the disease. These results highlight the significance of a large fraction of the population needing to wear face masks to effectively reduce the spread of the epidemic. The simulations show that early implementation of mask policy using moderate-quality masks is more effective than a later implementation with high-quality masks. These findings may inform public health mask-use policies for an infectious respiratory disease outbreak (such as one of COVID-19) in high-risk settings.

scholarly journals The role of mergers and interactions in driving the evolution of dwarf galaxies over cosmic time

2020 ◽  
Vol 500 (4) ◽  
pp. 4937-4957 ◽  
Author(s):  
G Martin ◽  
R A Jackson ◽  
S Kaviraj ◽  
H Choi ◽  
J E G Devriendt ◽  
...  
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
Large Fraction ◽  
Structural Evolution ◽  
Cosmic Time ◽  
Stellar Mass ◽  
High Mass ◽  
Key Drivers ◽  
Mass Assembly

ABSTRACT Dwarf galaxies (M⋆ &lt; 109 M⊙) are key drivers of mass assembly in high-mass galaxies, but relatively little is understood about the assembly of dwarf galaxies themselves. Using the NewHorizon cosmological simulation (∼40 pc spatial resolution), we investigate how mergers and fly-bys drive the mass assembly and structural evolution of around 1000 field and group dwarfs up to z = 0.5. We find that, while dwarf galaxies often exhibit disturbed morphologies (5 and 20 per cent are disturbed at z = 1 and z = 3 respectively), only a small proportion of the morphological disturbances seen in dwarf galaxies are driven by mergers at any redshift (for 109 M⊙, mergers drive under 20 per cent morphological disturbances). They are instead primarily the result of interactions that do not end in a merger (e.g. fly-bys). Given the large fraction of apparently morphologically disturbed dwarf galaxies which are not, in fact, merging, this finding is particularly important to future studies identifying dwarf mergers and post-mergers morphologically at intermediate and high redshifts. Dwarfs typically undergo one major and one minor merger between z = 5 and z = 0.5, accounting for 10 per cent of their total stellar mass. Mergers can also drive moderate star formation enhancements at lower redshifts (3 or 4 times at z = 1), but this accounts for only a few per cent of stellar mass in the dwarf regime given their infrequency. Non-merger interactions drive significantly smaller star formation enhancements (around two times), but their preponderance relative to mergers means they account for around 10 per cent of stellar mass formed in the dwarf regime.

scholarly journals How robustly can we constrain the low-mass end of the z ∼ 6−7 stellar mass function? The limits of lensing models and stellar population assumptions in the Hubble Frontier Fields

2020 ◽  
Vol 501 (2) ◽  
pp. 1568-1590
Author(s):  
Lukas J Furtak ◽  
Hakim Atek ◽  
Matthew D Lehnert ◽  
Jacopo Chevallard ◽  
Stéphane Charlot
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Stellar Mass ◽  
Star Formation History ◽  
Space Telescope ◽  
Formation History ◽  
Low Mass ◽  
Stellar Masses ◽  
Dust Attenuation ◽  
The Impact

ABSTRACT We present new measurements of the very low mass end of the galaxy stellar mass function (GSMF) at z ∼ 6−7 computed from a rest-frame ultraviolet selected sample of dropout galaxies. These galaxies lie behind the six Hubble Frontier Field clusters and are all gravitationally magnified. Using deep Spitzer/IRAC and Hubble Space Telescope imaging, we derive stellar masses by fitting galaxy spectral energy distributions and explore the impact of different model assumptions and parameter degeneracies on the resulting GSMF. Our sample probes stellar masses down to $M_{\star }\gt 10^{6}\, \text{M}_{\odot}$ and we find the z ∼ 6−7 GSMF to be best parametrized by a modified Schechter function that allows for a turnover at very low masses. Using a Monte Carlo Markov chain analysis of the GSMF, including accurate treatment of lensing uncertainties, we obtain a relatively steep low-mass end slope $\alpha \simeq -1.96_{-0.08}^{+0.09}$ and a turnover at $\log (M_T/\text{M}_{\odot})\simeq 7.10_{-0.56}^{+0.17}$ with a curvature of $\beta \simeq 1.00_{-0.73}^{+0.87}$ for our minimum assumption model with constant star formation history (SFH) and low dust attenuation, AV ≤ 0.2. We find that the z ∼ 6−7 GSMF, in particular its very low mass end, is significantly affected by the assumed functional form of the star formation history and the degeneracy between stellar mass and dust attenuation. For example, the low-mass end slope ranges from $\alpha \simeq -1.82_{-0.07}^{+0.08}$ for an exponentially rising SFH to $\alpha \simeq -2.34_{-0.10}^{+0.11}$ when allowing AV of up to 3.25. Future observations at longer wavelengths and higher angular resolution with the James Webb Space Telescope are required to break these degeneracies and to robustly constrain the stellar mass of galaxies on the extreme low-mass end of the GSMF.

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