The evolution in the stellar mass of brightest cluster galaxies over the past 10 billion years

Context. At low redshift, early-type galaxies often exhibit a rising flux with decreasing wavelength in the 1000–2500 Å range, called “UV upturn”. The origin of this phenomenon is debated, and its evolution with redshift is poorly constrained. The observed GALEX FUV-NUV color can be used to probe the UV upturn approximately to redshift 0.5.Aim. We provide constraints on the existence of the UV upturn up to redshift ~0.4 in the brightest cluster galaxies (BCG) located behind the Virgo cluster, using data from the GUViCS survey.Methods. We estimate the GALEX far-UV (FUV) and near-UV (NUV) observed magnitudes for BCGs from the maxBCG catalog in the GUViCS fields. We increase the number of nonlocal galaxies identified as BCGs with GALEX photometry from a few tens of galaxies to 166 (64 when restricting this sample to relatively small error bars). We also estimate a central color within a 20 arcsec aperture. By using the r-band luminosity from the maxBCG catalog, we can separate blue FUV-NUV due to recent star formation and candidate upturn cases. We use Lick indices to verify their similarity to redshift 0 upturn cases.Results. We clearly detect a population of blue FUV-NUV BCGs in the redshift range 0.10–0.35, vastly improving the existing constraints at these epochs by increasing the number of galaxies studied, and by exploring a redshift range with no previous data (beyond 0.2), spanning one more Gyr in the past. These galaxies bring new constraints that can help distinguish between assumptions concerning the stellar populations causing the UV upturn phenomenon. The existence of a large number of UV upturns around redshift 0.25 favors the existence of a binary channel among the sources proposed in the literature.

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Dynamical masses of brightest cluster galaxies – II. Constraints on the stellar IMF

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3530 ◽

2020 ◽

Vol 500 (3) ◽

pp. 4153-4165

Author(s):

S I Loubser ◽

H Hoekstra ◽

A Babul ◽

Y M Bahé ◽

M Donahue

Keyword(s):

Gravitational Lensing ◽

Stellar Population ◽

Population Analysis ◽

Stellar Populations ◽

Stellar Mass ◽

Initial Mass Function ◽

Dynamical Mass ◽

Cluster Galaxies ◽

Brightest Cluster Galaxies ◽

Mass Profiles

ABSTRACT We use stellar and dynamical mass profiles, combined with a stellar population analysis, of 32 brightest cluster galaxies (BCGs) at redshifts of 0.05 ≤$z$ ≤ 0.30, to place constraints on their stellar initial mass function (IMF). We measure the spatially resolved stellar population properties of the BCGs, and use it to derive their stellar mass-to-light ratios ($\Upsilon _{\star \rm POP}$). We find young stellar populations (<200 Myr) in the centres of 22 per cent of the sample, and constant $\Upsilon _{\star \rm POP}$ within 15 kpc for 60 per cent of the sample. We further use the stellar mass-to-light ratio from the dynamical mass profiles of the BCGs ($\Upsilon _{\star \rm DYN}$), modelled using a multi-Gaussian expansion and Jeans Anisotropic Method, with the dark matter contribution explicitly constrained from weak gravitational lensing measurements. We directly compare the stellar mass-to-light ratios derived from the two independent methods, $\Upsilon _{\star \rm POP}$ (assuming some IMF) to $\Upsilon _{\star \rm DYN}$ for the subsample of BCGs with no young stellar populations and constant $\Upsilon _{\star \rm POP}$. We find that for the majority of these BCGs, a Salpeter (or even more bottom-heavy) IMF is needed to reconcile the stellar population and dynamical modelling results although for a small number of BCGs, a Kroupa (or even lighter) IMF is preferred. For those BCGs better fit with a Salpeter IMF, we find that the mass-excess factor against velocity dispersion falls on an extrapolation (towards higher masses) of known literature correlations. We conclude that there is substantial scatter in the IMF amongst the highest mass galaxies.

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Rapid early coeval star formation and assembly of the most-massive galaxies in the Universe

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa541 ◽

2020 ◽

Vol 493 (4) ◽

pp. 4607-4621 ◽

Cited By ~ 2

Author(s):

Douglas Rennehan ◽

Arif Babul ◽

Christopher C Hayward ◽

Connor Bottrell ◽

Maan H Hani ◽

...

Keyword(s):

Stellar Mass ◽

Cluster Galaxies ◽

Massive Galaxies ◽

James Webb Space Telescope ◽

Brightest Cluster Galaxies ◽

Virial Mass ◽

Formation And Evolution ◽

Hydrodynamical Simulations ◽

Observational Techniques ◽

Near Future

Abstract The current consensus on the formation and evolution of the brightest cluster galaxies is that their stellar mass forms early ($z$ ≳ 4) in separate galaxies that then eventually assemble the main structure at late times ($z$ ≲ 1). However, advances in observational techniques have led to the discovery of protoclusters out to $z$ ∼ 7. If these protoclusters assemble rapidly in the early Universe, they should form the brightest cluster galaxies much earlier than suspected by the late-assembly picture. Using a combination of observationally constrained hydrodynamical and dark-matter-only simulations, we show that the stellar assembly time of a sub-set of brightest cluster galaxies occurs at high redshifts ( $z$ > 3) rather than at low redshifts ($z$ < 1), as is commonly thought. We find, using isolated non-cosmological hydrodynamical simulations, that highly overdense protoclusters assemble their stellar mass into brightest cluster galaxies within ∼1 Gyr of evolution – producing massive blue elliptical galaxies at high redshifts ($z$ ≳ 1.5). We argue that there is a downsizing effect on the cluster scale wherein some of the brightest cluster galaxies in the cores of the most-massive clusters assemble earlier than those in lower mass clusters. In those clusters with $z$ = 0 virial mass ≥ 5 × 1014 M⊙, we find that $9.8{{\ \rm per\ cent}}$ have their cores assembly early, and a higher fraction of $16.4{{\ \rm per\ cent}}$ in those clusters above 1015 M⊙. The James Webb Space Telescope will be able to detect and confirm our prediction in the near future, and we discuss the implications to constraining the value of σ8.

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Molecular gas in distant brightest cluster galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936148 ◽

2020 ◽

Vol 635 ◽

pp. A32 ◽

Cited By ~ 2

Author(s):

G. Castignani ◽

F. Combes ◽

P. Salomé ◽

J. Freundlich

Keyword(s):

Star Formation ◽

Stellar Mass ◽

Star Formation History ◽

Gas Content ◽

Molecular Gas ◽

Distant Cluster ◽

Cluster Galaxies ◽

Star Forming ◽

Distant Star ◽

Brightest Cluster Galaxies

The mechanisms governing the stellar mass assembly and star formation history of brightest cluster galaxies (BCGs) are still being debated. By means of new and archival molecular gas observations we investigate the role of dense megaparsec-scale environments in regulating the fueling of star formation in distant BCGs, through cosmic time. We observed in CO with the IRAM 30 m telescope two star-forming BCGs belonging to SpARCS clusters, namely, 3C 244.1 (z = 0.4) and SDSS J161112.65+550823.5 (z = 0.9), and compared their molecular gas and star formation properties with those of a compilation of ∼100 distant cluster galaxies from the literature, including nine additional distant BCGs at z ∼ 0.4 − 3.5. We set robust upper limits of MH2 < 1.0 × 1010 M⊙ and < 2.8 × 1010 M⊙ to their molecular gas content, respectively, and to the ratio of molecular gas to stellar mass M(H2)/M⋆ ≲ 0.2 and depletion time τdep ≲ 40 Myr of the two targeted BCGs. They are thus among the distant cluster galaxies with the lowest gas fractions and shortest depletion times. The majority (64%±15% and 73%±18%) of the 11 BCGs with observations in CO have lower M(H2)/M⋆ values and τdep, respectively, than those estimated for main sequence galaxies. Statistical analysis also tentatively suggests that the values of M(H2)/M⋆ and τdep for the 11 BCGs deviates, with a significance of ∼2σ, from those of the comparison sample of cluster galaxies. A morphological analysis for a subsample of seven BCGs with archival HST observations reveals that 71%±17% of the BCGs are compact or show star-forming components or substructures. Our results suggest a scenario where distant star-forming BCGs assemble a significant fraction ∼16% of their stellar mass on the relatively short timescale ∼τdep, while environmental mechanisms might prevent the replenishment of gas feeding the star formation. We speculate that compact components also favor the rapid exhaustion of molecular gas and ultimately help to quench the BCGs. Distant star-forming BCGs are excellent targets for ALMA and for next-generation telescopes such as the James Webb Space Telescope.

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THE STELLAR MASS GROWTH OF BRIGHTEST CLUSTER GALAXIES IN THE IRAC SHALLOW CLUSTER SURVEY

The Astrophysical Journal ◽

10.1088/0004-637x/771/1/61 ◽

2013 ◽

Vol 771 (1) ◽

pp. 61 ◽

Cited By ~ 51

Author(s):

Yen-Ting Lin ◽

Mark Brodwin ◽

Anthony H. Gonzalez ◽

Paul Bode ◽

Peter R. M. Eisenhardt ◽

...

Keyword(s):

Stellar Mass ◽

Mass Growth ◽

Cluster Galaxies ◽

Cluster Survey ◽

Brightest Cluster Galaxies

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The K-Band Hubble Diagram for the Brightest Cluster Galaxies: A Test of Galaxy Formation Models

Symposium - International Astronomical Union ◽

10.1017/s007418090011321x ◽

1999 ◽

Vol 186 ◽

pp. 407-407

Author(s):

A. Aragón-Salamanca ◽

C.M. Baugh ◽

G. Kauffmann

Keyword(s):

Galaxy Formation ◽

Stellar Mass ◽

Hubble Diagram ◽

Redshift Range ◽

Cluster Galaxies ◽

Brightest Cluster Galaxies ◽

Galaxy Formation And Evolution ◽

Absolute Magnitudes ◽

Luminosity Evolution ◽

K Band

We analyze the K-band Hubble diagram for a sample of brightest cluster galaxies (BCGs) in the redshift range 0 < z < 1. We confirm that the scatter in the absolute magnitudes of the galaxies is small (0.3 magnitudes). The BCGs exhibit very little luminosity evolution in this redshift range: if q0 = 0.0 we detect no luminosity evolution; for q0 = 0.5 we measure a small negative evolution (i.e., BCGs were about 0.5 magnitudes fainter at z = 1 than today). If the mass in stars of these galaxies had remained constant over this period of time, substantial positive luminosity evolution would be expected: BCGs should have been brighter in the past since their stars were younger. A likely explanation for the observed zero or negative evolution is that the stellar mass of the BCGs has been assembled over time through merging and accretion, as expected in hierarchical models of galaxy formation. The colour evolution of the BCGs is consistent with that of an old stellar population (zform > 2) that is evolving passively. We can thus use evolutionary population synthesis models to estimate the rate of growth in stellar mass for these systems. We find that the stellar mass in a typical BCG has grown by a factor ≃ 2 since z ≃ 1 if q0 = 0.0 or by factor ≃ 4 if q0 = 0.5. These results are in remarkably good agreement with the predictions of semi-analytic models of galaxy formation and evolution set in the context of a hierarchical scenario for structure formation.

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