scholarly journals Molecular gas in CLASH brightest cluster galaxies at z ∼ 0.2 – 0.9

2020 ◽  
Vol 640 ◽  
pp. A65 ◽  
Author(s):  
G. Castignani ◽  
M. Pandey-Pommier ◽  
S. L. Hamer ◽  
F. Combes ◽  
P. Salomé ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Formation Rate ◽  
Molecular Gas ◽  
Gas Reservoirs ◽  
Large Reservoir ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Brightest Cluster Galaxies ◽  
Upper Limits ◽  
High Level

Brightest cluster galaxies (BCGs) are excellent laboratories for the study of galaxy evolution in dense Mpc-scale environments. We used the IRAM-30 m to observe, in CO(1→0), CO(2→1), CO(3→2), or CO(4→3), 18 BCGs at z ∼ 0.2 − 0.9 drawn from the Cluster Lensing And Supernova survey with Hubble (CLASH) survey. Our sample includes RX1532, which is our primary target as it is among the BCGs with the highest star formation rate (SFR ≳100 M⊙ yr−1) in the CLASH sample. We unambiguously detected both CO(1→0) and CO(3→2) in RX1532, yielding a large reservoir of molecular gas, MH2 = (8.7 ± 1.1)×1010 M⊙, and a high level of excitation, r31 = 0.75 ± 0.12. A morphological analysis of the Hubble Space Telescope I-band image of RX1532 reveals the presence of clumpy substructures both within and outside the half-light radius re = (11.6 ± 0.3) kpc, similarly to those found independently both in ultraviolet and in Hα in previous works. We tentatively detected CO(1→0) or CO(2→1) in four other BCGs, with molecular gas reservoirs in the range of MH2 = 2 × 1010 − 11 M⊙. For the remaining 13 BCGs, we set robust upper limits of MH2/M⋆ ≲ 0.1, which are among the lowest molecular-gas-to-stellar-mass ratios found for distant ellipticals and BCGs. In comparison with distant cluster galaxies observed in CO, our study shows that RX1532 (MH2/M⋆ = 0.40 ± 0.05) belongs to the rare population of star-forming and gas-rich BCGs in the distant universe. By using the available X-ray based estimates of the central intra-cluster medium entropy, we show that the detection of large reservoirs of molecular gas MH2 ≳ 1010 M⊙ in distant BCGs is possible when the two conditions are met: (i) high SFR and (ii) low central entropy, which favors the condensation and the inflow of gas onto the BCGs themselves, similarly to what has been previously found for some local BCGs.

scholarly journals Large Molecular Gas Reservoirs in Star-forming Cluster Galaxies

2019 ◽  
Vol 882 (2) ◽  
pp. 132 ◽  
Author(s):  
Joseph Cairns ◽  
Andra Stroe ◽  
Carlos De Breuck ◽  
Tony Mroczkowski ◽  
David Clements
Keyword(s):  
Molecular Gas ◽  
Gas Reservoirs ◽  
Cluster Galaxies ◽  
Star Forming

scholarly journals The EDGE-CALIFA survey: exploring the role of molecular gas on galaxy star formation quenching

2020 ◽  
Vol 644 ◽  
pp. A97
Author(s):  
D. Colombo ◽  
S. F. Sanchez ◽  
A. D. Bolatto ◽  
V. Kalinova ◽  
A. Weiß ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Large Scale ◽  
Formation Rate ◽  
Molecular Gas ◽  
Star Forming ◽  
Average Value ◽  
First Results ◽  
Gas Consumption ◽  
Formation Efficiency

Understanding how galaxies cease to form stars represents an outstanding challenge for galaxy evolution theories. This process of “star formation quenching” has been related to various causes, including active galactic nuclei activity, the influence of large-scale dynamics, and the environment in which galaxies live. In this paper, we present the first results from a follow-up of CALIFA survey galaxies with observations of molecular gas obtained with the APEX telescope. Together with the EDGE-CARMA observations, we collected 12CO observations that cover approximately one effective radius in 472 CALIFA galaxies. We observe that the deficit of galaxy star formation with respect to the star formation main sequence (SFMS) increases with the absence of molecular gas and with a reduced efficiency of conversion of molecular gas into stars, which is in line with the results of other integrated studies. However, by dividing the sample into galaxies dominated by star formation and galaxies quenched in their centres (as indicated by the average value of the Hα equivalent width), we find that this deficit increases sharply once a certain level of gas consumption is reached, indicating that different mechanisms drive separation from the SFMS in star-forming and quenched galaxies. Our results indicate that differences in the amount of molecular gas at a fixed stellar mass are the primary drivers for the dispersion in the SFMS, and the most likely explanation for the start of star formation quenching. However, once a galaxy is quenched, changes in star formation efficiency drive how much a retired galaxy differs in its star formation rate from star-forming ones of similar masses. In other words, once a paucity of molecular gas has significantly reduced star formation, changes in the star formation efficiency are what drives a galaxy deeper into the red cloud, hence retiring it.

scholarly journals Molecular gas in distant brightest cluster galaxies

2020 ◽  
Vol 635 ◽  
pp. A32 ◽  
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.

scholarly journals AlFoCS + Fornax3D: resolved star formation in the Fornax cluster with ALMA and MUSE

2020 ◽  
Vol 496 (2) ◽  
pp. 2155-2182 ◽  
Author(s):  
N Zabel ◽  
T A Davis ◽  
M Sarzi ◽  
Boris Nedelchev ◽  
M Chevance ◽  
...  
Keyword(s):  
Star Formation ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Mass Range ◽  
Stellar Mass ◽  
Small Scale ◽  
Molecular Gas ◽  
Gas Reservoirs ◽  
Cluster Galaxies ◽  
Fornax Cluster

ABSTRACT We combine data from ALMA and MUSE to study the resolved (∼300 pc scale) star formation relation (star formation rate, SFR, versus molecular gas surface density) in cluster galaxies. Our sample consists of nine Fornax cluster galaxies, including spirals, ellipticals, and dwarfs, covering a stellar mass range of ∼108.8–1011 M⊙. CO(1-0) and extinction corrected Hα were used as tracers for the molecular gas mass and SFR, respectively. We compare our results with Kennicutt and Bigiel et al. Furthermore, we create depletion time maps to reveal small-scale variations in individual galaxies. We explore these further in FCC290, using the ‘uncertainty principle for star formation’ (Kruijssen & Longmore) to estimate molecular cloud lifetimes, which we find to be short (&lt;10 Myr) in this galaxy. Galaxy-averaged depletion times are compared with other parameters such as stellar mass and cluster-centric distance. We find that the star formation relation in the Fornax cluster is close to those from Kennicutt and Bigiel et al., but overlaps mostly with the shortest depletion times predicted by Bigiel et al. This slight decrease in depletion time is mostly driven by dwarf galaxies with disturbed molecular gas reservoirs close to the virial radius. In FCC90, a dwarf galaxy with a molecular gas tail, we find that depletion times are a factor ≳10 higher in its tail than in its stellar body.

scholarly journals Toward unveiling internal properties of Hii regions and their connections at the cosmic noon era

2015 ◽  
Vol 11 (S319) ◽  
pp. 53-53
Author(s):  
Rhythm Shimakawa ◽  
Tadayuki Kodama ◽  
Masao Hayashi ◽  
Ken-ichi Tadaki ◽  
Tomoko L. Suzuki ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Near Infrared ◽  
Formation Rate ◽  
Physical Parameters ◽  
Star Forming ◽  
Radiation Fields ◽  
Star Forming Regions ◽  
Physical Scale ◽  
High Level

AbstractThe redshift interval z = 2–3 is known as the cosmic noon that is the most active era of star formation across the Universe (Hopkins & Beacom 2006). In the past decade, many authors have investigated global properties of star-forming (SF) galaxies in this turbulent era, such as gas fractions and gaseous metallicities (e.g. Erb et al. 2006). With those achievements, we are going on to the next stage to understand more details i.e. those physical parameters in star-forming regions. Recent advent of near-infrared instruments typified by MOSFIRE on the Keck telescope, enable us with identifying the physical parameters of Hii regions in ‘typical’ SF galaxies individually (Steidel et al. 2014). Recent highlights suggest higher electron densities, higher ionization parameters, and harder UV radiation fields may be common.In order to know how galaxy evolution physically correlates with the natures of their star-forming regions, we have explored relationships between the electron density (ne) of ionized gas from the oxygen line ratio and other physical properties, based on the deep spectra of Hα emitters at z = 2.5 by the MOSFIRE. MOSFIRE for the first time provides ne of the galaxies at high-z with a high level of confidence. The result shows the specific star formation rate (sSFR) and the SFR surface density (ΣSFR) are correlated with ne (Shimakawa et al. 2015). The ne-ΣSFR relation could be linked to the star formation law in Hii regions if we assume that hydrogen in Hii regions is fully-ionized. Otherwise, more active star formation per unit area (higher ΣSFRs), may cause higher ionization states. However, we need some specific concerns that obtained physical parameters should depend on the scale dependence, since typical size of Hii region is only <100 pc despite that we study physical states of entire galaxies. Thus we obtain surface-brightness-weighted and ensemble averaged line fluxes for the entire galaxy or the part that falls into the slit width (a few kpc scale size). The thirty meter telescope (TMT) is a powerful instrument to resolve such a difficulty, since its spatial resolution reaches <100 pc on the physical scale at z ~ 2 by AO assistance.

scholarly journals H2 content of galaxies inside and around intermediate redshift clusters

2019 ◽  
Vol 15 (S359) ◽  
pp. 158-162
Author(s):  
Damien Spérone-Longin
Keyword(s):  
Star Formation ◽  
Large Fraction ◽  
Formation Rate ◽  
Gas Content ◽  
Cluster Center ◽  
Molecular Gas ◽  
Ample Evidence ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Medium Mass

AbstractDense environments have an impact on the star formation rate of galaxies. As stars form from molecular gas, looking at the cold molecular gas content of a galaxy gives useful insights on its efficiency in forming stars. However, most galaxies observed in CO (a proxy for the cold molecular gas content) at intermediate redshifts, are field galaxies. Only a handful of studies focused on cluster galaxies. I present new results on the environment of one medium mass cluster from the EDisCS survey at z ˜ 0.5. 27 star-forming galaxies were selected to evenly sample the range of densities encountered inside and around the cluster. We cover a region extending as far as 8 virial radii from the cluster center. Indeed there is ample evidence that star formation quenching starts already beyond 3 cluster virial radii. I discuss our CO(3-2) ALMA observations, which unveil a large fraction of galaxies with low gas-to-stellar mass ratios.

scholarly journals The “entropy floor” is porous – remarks on the coexistence of star formation and kinetic AGN feedback

2013 ◽  
Vol 9 (S304) ◽  
pp. 331-334
Author(s):  
Grant R. Tremblay
Keyword(s):  
Star Formation ◽  
Hubble Space Telescope ◽  
Formation Rate ◽  
Mechanical Power ◽  
Continuum Emission ◽  
Morphological Evidence ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Brightest Cluster Galaxies ◽  
Far Ultraviolet

AbstractWe discuss the morphology of star forming clouds and filaments in the central (≲ 50 kpc) regions of 16 low redshift (z<0.3) cool core brightest cluster galaxies (BCGs). The sample spans decades-wide ranges of X-ray mass deposition and star formation rates as well as active galactic nucleus (AGN) mechanical power, encompassing both high and low extremes of the supposed intracluster medium (ICM) cooling and AGN heating feedback cycle. Amid evidence that the gas fueling both star formation and AGN activity has condensed from the hot atmosphere, we present new and archival Hubble Space Telescope (HST) images of far ultraviolet (FUV) continuum emission directly associated with young stars, acting as a calorimeter for the degree to which the suppression of star formation by AGN mechanical feedback may be spatially or temporally inefficient. We discuss evidence for temporal and possibly cyclical variation in star formation rate, wherein elevated cooling episodes are permitted when AGN feedback is in a low-power state, and vice-versa. Several sources exhibit strong morphological evidence that low levels of star formation can survive and may indeed be triggered by the passage of a propagating radio source. We conclude by discussing the apparent coexistence of feedback and star formation. If AGN mechanical power does establish an “entropy floor”, this floor must be porous, or raise and lower as the AGN varies in power.

scholarly journals A CO Survey of SpARCS Star-forming Brightest Cluster Galaxies: Evidence for Uniformity in BCG Molecular Gas Processing across Cosmic Time

2021 ◽  
Vol 909 (2) ◽  
pp. L29
Author(s):  
Delaney A. Dunne ◽  
Tracy M. A. Webb ◽  
Allison Noble ◽  
Christopher Lidman ◽  
Heath Shipley ◽  
...  
Keyword(s):  
Cosmic Time ◽  
Molecular Gas ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Gas Processing ◽  
Brightest Cluster Galaxies

Cold gas studies of a z = 2.5 protocluster

2020 ◽  
Vol 15 (S359) ◽  
pp. 136-140
Author(s):  
Minju M. Lee ◽  
Ichi Tanaka ◽  
Rohei Kawabe
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
Kinematic Model ◽  
Molecular Gas ◽  
General View ◽  
Massive Galaxies ◽  
Star Forming ◽  
Gas Kinematics ◽  
Narrow Band Filter ◽  
Stellar Masses

AbstractWe present studies of a protocluster at z =2.5, an overdense region found close to a radio galaxy, 4C 23.56, using ALMA. We observed 1.1 mm continuum, two CO lines (CO (4–3) and CO (3–2)) and the lower atomic carbon line transition ([CI](3P1-3P0)) at a few kpc (0″.3-0″.9) resolution. The primary targets are 25 star-forming galaxies selected as Hα emitters (HAEs) that are identified with a narrow band filter. These are massive galaxies with stellar masses of > 1010Mʘ that are mostly on the galaxy main sequence at z =2.5. We measure the molecular gas mass from the independent gas tracers of 1.1 mm, CO (3–2) and [CI], and investigate the gas kinematics of galaxies from CO (4–3). Molecular gas masses from the different measurements are consistent with each other for detection, with a gas fraction (fgas = Mgas/(Mgas+ Mstar)) of ≃ 0.5 on average but with a caveat. On the other hand, the CO line widths of the protocluster galaxies are typically broader by ˜50% compared to field galaxies, which can be attributed to more frequent, unresolved gas-rich mergers and/or smaller sizes than field galaxies, supported by our high-resolution images and a kinematic model fit of one of the galaxies. We discuss the expected scenario of galaxy evolution in protoclusters at high redshift but future large surveys are needed to get a more general view.

scholarly journals Quenching by gas compression and consumption

2019 ◽  
Vol 624 ◽  
pp. A81 ◽  
Author(s):  
Allison W. S. Man ◽  
Matthew D. Lehnert ◽  
Joël D. R. Vernet ◽  
Carlos De Breuck ◽  
Theresa Falkendal
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Relative Strength ◽  
Star Formation History ◽  
Molecular Gas ◽  
Host Galaxies ◽  
Massive Galaxies ◽  
Star Forming ◽  
Gas Compression ◽  
Formation History

The objective of this work is to study how active galactic nuclei (AGN) influence star formation in host galaxies. We present a detailed investigation of the star-formation history and conditions of a z = 2.57 massive radio galaxy based on VLT/X-shooter and ALMA observations. The deep rest-frame ultraviolet spectrum contains photospheric absorption lines and wind features indicating the presence of OB-type stars. The most significantly detected photospheric features are used to characterize the recent star formation: neither instantaneous nor continuous star-formation history is consistent with the relative strength of the Si IIλ1485 and S Vλ1502 absorption. Rather, at least two bursts of star formation took place in the recent past, at 6+1-2 Myr and ≳20 Myr ago, respectively. We deduce a molecular H2 gas mass of (3.9 ± 1.0) × 1010 M⊙ based on ALMA observations of the [C I] 3P2−3P1 emission. The molecular gas mass is only 13% of its stellar mass. Combined with its high star-formation rate of (1020-170+190 M⊙ yr-1, this implies a high star-formation efficiency of (26 ± 8) Gyr−1 and a short depletion time of (38 ± 12) Myr. We attribute the efficient star formation to compressive gas motions in order to explain the modest velocity dispersions (⩽55 km s−1) of the photospheric lines and of the star-forming gas traced by [C I]. Because of the likely very young age of the radio source, our findings suggest that vigorous star formation consumes much of the gas and works in concert with the AGN to remove any residual molecular gas, and eventually quenching star formation in massive galaxies.

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