scholarly journals No signs of star formation being regulated in the most luminous quasars at z ∼ 2 with ALMA

2019 ◽  
Vol 488 (1) ◽  
pp. 1180-1198 ◽  
Author(s):  
Andreas Schulze ◽  
John D Silverman ◽  
Emanuele Daddi ◽  
Wiphu Rujopakarn ◽  
Daizhong Liu ◽  
...  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Continuum Emission ◽  
Gas Reservoir ◽  
Star Forming ◽  
Gas Processing ◽  
The Mean ◽  
Stellar Masses

ABSTRACT We present ALMA Band 7 observations at $850\, \mu$m of 20 luminous ($\log \, L_{\rm bol}\,\gt\, 46.9$ [erg s−1]) unobscured quasars at z ∼ 2. We detect continuum emission for 19/20 quasars. After subtracting an AGN contribution, we measure the total far-IR luminosity for 18 quasars, assuming a modified blackbody model, and attribute the emission as indicative of the star formation rate (SFR). Our sample can be characterized with a lognormal SFR distribution having a mean of 140 M⊙ yr−1 and a dispersion of 0.5 dex. Based on an inference of their stellar masses, the SFRs are similar, in both the mean and dispersion, with star-forming main-sequence galaxies at the equivalent epoch. Thus, there is no evidence for a systematic enhancement or suppression (i.e. regulation or quenching) of star formation in the hosts of the most luminous quasars at z ∼ 2. These results are consistent with the Magneticum cosmological simulation, while in disagreement with a widely recognized phenomenological model that predicts higher SFRs than observed here based on the high bolometric luminosities of this sample. Furthermore, there is only a weak relation between SFR and accretion rate on to their supermassive black holes both for average and individual measurements. We interpret these results as indicative of star formation and quasar accretion being fed from the available gas reservoir(s) in their host with a disconnect due to their different physical sizes, temporal scales, and means of gas processing.

scholarly journals Effect of the environment on star formation activity and stellar mass for star-forming galaxies in the COSMOS field

2020 ◽  
Vol 499 (1) ◽  
pp. 948-956
Author(s):  
S M Randriamampandry ◽  
M Vaccari ◽  
K M Hess
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Cosmic Time ◽  
Stellar Mass ◽  
Star Forming ◽  
Galaxy Environment ◽  
Stellar Masses ◽  
The Relationship

ABSTRACT We investigate the relationship between the environment and the galaxy main sequence (the relationship between stellar mass and star formation rate), as well as the relationship between the environment and radio luminosity ($P_{\rm 1.4\, GHz}$), to shed new light on the effects of the environment on galaxies. We use the VLA-COSMOS 3-GHz catalogue, which consists of star-forming galaxies and quiescent galaxies (active galactic nuclei) in three different environments (field, filament, cluster) and for three different galaxy types (satellite, central, isolated). We perform for the first time a comparative analysis of the distribution of star-forming galaxies with respect to the main-sequence consensus region from the literature, taking into account galaxy environment and using radio observations at 0.1 ≤ z ≤ 1.2. Our results corroborate that the star formation rate is declining with cosmic time, which is consistent with the literature. We find that the slope of the main sequence for different z and M* bins is shallower than the main-sequence consensus, with a gradual evolution towards higher redshift bins, irrespective of environment. We see no trends for star formation rate in either environment or galaxy type, given the large errors. In addition, we note that the environment does not seem to be the cause of the flattening of the main sequence at high stellar masses for our sample.

scholarly journals Massive molecular gas reservoir around the central AGN in the CARLA J1103 + 3449 cluster at z = 1.44

2020 ◽  
Vol 641 ◽  
pp. A22
Author(s):  
Vladan Markov ◽  
Simona Mei ◽  
Philippe Salomé ◽  
Françoise Combes ◽  
Daniel Stern ◽  
...  
Keyword(s):  
Star Formation ◽  
Spectral Index ◽  
Main Sequence ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Cluster Core ◽  
Continuum Emission ◽  
Molecular Gas ◽  
Early Type ◽  
Gas Reservoir

Passive early-type galaxies dominate cluster cores at z ≲ 1.5. At higher redshift, cluster core galaxies are observed to have on-going star-formation, which is fueled by cold molecular gas. We measured the molecular gas reservoir of the central region around the radio-loud active galactic nucleus (AGN) in the cluster CARLA J1103 + 3449 at z = 1.44 using NOEMA. The AGN synchrotron emission dominates the continuum emission at 94.48 GHz, and we measured its flux at the AGN position and at the position of two radio jets. Combining our measurements with published results over the range 4.71–94.5 GHz, and assuming Ssynch ∝ ν−α, we obtain a flat spectral index of α = 0.14 ± 0.03 for the AGN core emission, and a steeper index of α = 1.43 ± 0.04 and α = 1.15 ± 0.04 at positions close to the western and eastern lobes, respectively. The total spectral index is α = 0.92 ± 0.02 over the range 73.8 MHz–94.5 GHz. We detect two CO(2–1) emission lines, both blueshifted with respect to the AGN. Their emission corresponds to two regions, ~17 kpc southeast and ~14 kpc southwest of the AGN, not associated with galaxies. In these two regions, we find a total massive molecular gas reservoir of Mgastot = 3.9 ± 0.4 × 1010 M⊙, which dominates (≳60%) the central total molecular gas reservoir. These results can be explained by massive cool gas flows in the center of the cluster. The AGN early-type host is not yet quenched; its star formation rate is consistent with being on the main sequence of star-forming galaxies in the field (star formation rate ~30–140 M⊙ yr−1), and the cluster core molecular gas reservoir is expected to feed the AGN and the host star formation before quiescence. The other confirmed cluster members show star formation rates at ~2σ below the field main sequence at similar redshifts and do not have molecular gas masses larger than galaxies of similar stellar mass in the field.

scholarly journals xGASS: cold gas content and quenching in galaxies below the star-forming main sequence

2020 ◽  
Vol 493 (2) ◽  
pp. 1982-1995 ◽  
Author(s):  
Steven Janowiecki ◽  
Barbara Catinella ◽  
Luca Cortese ◽  
Amelie Saintonge ◽  
Jing Wang
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Gas Content ◽  
Gas Reservoirs ◽  
Star Forming ◽  
Correct Model ◽  
Gas Measurements ◽  
Cold Gas

ABSTRACT We use H i and H2 global gas measurements of galaxies from xGASS and xCOLD GASS to investigate quenching paths of galaxies below the Star forming main sequence (SFMS). We show that the population of galaxies below the SFMS is not a 1:1 match with the population of galaxies below the H i and H2 gas fraction scaling relations. Some galaxies in the transition zone (TZ) 1σ below the SFMS can be as H i-rich as those in the SFMS, and have on average longer gas depletion time-scales. We find evidence for environmental quenching of satellites, but central galaxies in the TZ defy simple quenching pathways. Some of these so-called ‘quenched’ galaxies may still have significant gas reservoirs and be unlikely to deplete them any time soon. As such, a correct model of galaxy quenching cannot be inferred with star formation rate (or other optical observables) alone, but must include observations of the cold gas. We also find that internal structure (particularly, the spatial distribution of old and young stellar populations) plays a significant role in regulating the star formation of gas-rich isolated TZ galaxies, suggesting the importance of bulges in their evolution.

scholarly journals xGASS: the role of bulges along and across the local star-forming main sequence

2020 ◽  
Vol 493 (4) ◽  
pp. 5596-5605 ◽  
Author(s):  
Robin H W Cook ◽  
Luca Cortese ◽  
Barbara Catinella ◽  
Aaron Robotham
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Formation Rate ◽  
Stellar Mass ◽  
Local Universe ◽  
Star Forming ◽  
Star Formation Activity ◽  
The Galaxy ◽  
Stellar Masses

ABSTRACT We use our catalogue of structural decomposition measurements for the extended GALEX Arecibo SDSS Survey (xGASS) to study the role of bulges both along and across the galaxy star-forming main sequence (SFMS). We show that the slope in the sSFR–M⋆ relation flattens by ∼0.1 dex per decade in M⋆ when re-normalizing specifice star formation rate (sSFR) by disc stellar mass instead of total stellar mass. However, recasting the sSFR–M⋆ relation into the framework of only disc-specific quantities shows that a residual trend remains against disc stellar mass with equivalent slope and comparable scatter to that of the total galaxy relation. This suggests that the residual declining slope of the SFMS is intrinsic to the disc components of galaxies. We further investigate the distribution of bulge-to-total ratios (B/T) as a function of distance from the SFMS (ΔSFRMS). At all stellar masses, the average B/T of local galaxies decreases monotonically with increasing ΔSFRMS. Contrary to previous works, we find that the upper envelope of the SFMS is not dominated by objects with a significant bulge component. This rules out a scenario in which, in the local Universe, objects with increased star formation activity are simultaneously experiencing a significant bulge growth. We suggest that much of the discrepancies between different works studying the role of bulges originate from differences in the methodology of structurally decomposing galaxies.

scholarly journals Rejuvenated galaxies with very old bulges at the origin of the bending of the main sequence and of the ‘green valley’

2019 ◽  
Vol 489 (1) ◽  
pp. 1265-1290 ◽  
Author(s):  
Chiara Mancini ◽  
Emanuele Daddi ◽  
Stéphanie Juneau ◽  
Alvio Renzini ◽  
Giulia Rodighiero ◽  
...  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Formation Rate ◽  
Very Old ◽  
Massive Galaxies ◽  
Star Forming ◽  
Late Event ◽  
Age Of The Universe ◽  
Stellar Masses ◽  
Star Formation Histories

ABSTRACT We investigate the nature of star-forming galaxies with reduced specific star formation rate (sSFR) and high stellar masses, those ‘green valley’ objects that seemingly cause a reported bending, or flattening, of the star-forming main sequence. The fact that such objects host large bulges recently led some to suggest that the internal formation of bulges was a late event that induced the sSFRs of massive galaxies to drop in a slow downfall, and thus the main sequence to bend. We have studied in detail a sample of 10 galaxies at 0.45 < z < 1 with secure SFR from Herschel, deep Keck optical spectroscopy, and HST imaging from CANDELS allowing us to perform multiwavelength bulge to disc decomposition, and to derive star formation histories for the separated bulge and disc components. We find that the bulges hosted in these systems below main sequence are virtually all maximally old, with ages approaching the age of the Universe at the time of observation, while discs are young (〈 T50〉 ∼ 1.5 Gyr). We conclude that, at least based on our sample, the bending of the main sequence is, for a major part, due to rejuvenation, and we disfavour mechanisms that postulate the internal formation of bulges at late times. The very old stellar ages of our bulges suggest a number density of early-type galaxies at z = 1–3 higher than actually observed. If confirmed, this might represent one of the first direct validations of hierarchical assembly of bulges at high redshifts.

scholarly journals The Metal Abundances across Cosmic Time (MACT) Survey. III – The relationship between stellar mass and star formation rate in extremely low-mass galaxies

2020 ◽  
Vol 501 (2) ◽  
pp. 2231-2249 ◽  
Author(s):  
Kaitlyn Shin ◽  
Chun Ly ◽  
Matthew A Malkan ◽  
Sangeeta Malhotra ◽  
Mithi de los Reyes ◽  
...  
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Cosmic Time ◽  
Stellar Mass ◽  
Star Forming ◽  
Dependent Relation ◽  
Photometric Measurements ◽  
Stellar Masses

ABSTRACT Extragalactic studies have demonstrated that there is a moderately tight (≈0.3 dex) relationship between galaxy stellar mass (M⋆) and star formation rate (SFR) that holds for star-forming galaxies at M⋆ ∼ 3 × 108–1011 M⊙, i.e. the ‘star formation main sequence’. However, it has yet to be determined whether such a relationship extends to even lower mass galaxies, particularly at intermediate or higher redshifts. We present new results using observations for 714 narrow-band H α-selected galaxies with stellar masses between 106 and 1010 M⊙ (average of 108.2 M⊙) at z ≈ 0.07–0.5. These galaxies have sensitive ultraviolet (UV) to near-infrared photometric measurements and optical spectroscopy. The latter allows us to correct our H α SFRs for dust attenuation using Balmer decrements. Our study reveals that: (1) for low-SFR galaxies, our H α SFRs systematically underpredict compared to far-UV measurements, consistent with other studies; (2) at a given stellar mass (≈108 M⊙), log (specific SFR) evolves as A log (1 + z) with A = 5.26 ± 0.75, and on average, specific SFR increases with decreasing stellar mass; (3) the SFR–M⋆ relation holds for galaxies down to ∼106 M⊙ (∼1.5 dex below previous studies), and over lookback times of up to 5 Gyr, follows a redshift-dependent relation of log (SFR) ∝ α log (M⋆/M⊙) + β z with α = 0.60 ± 0.01 and β = 1.86 ± 0.07; and (4) the observed dispersion in the SFR–M⋆ relation at low stellar masses is ≈0.3 dex. Accounting for survey selection effects using simulated galaxies, we estimate that the true dispersion is ≈0.5 dex.

scholarly journals Galaxies in the first billion years: implications for re-ionization and the star formation history at z>6

2006 ◽  
Vol 2 (14) ◽  
pp. 248-248
Author(s):  
Andrew J. Bunker ◽  
Elizabeth R. Stanway ◽  
Laurence P. Eyles ◽  
Richard S. Ellis ◽  
Richard G. McMahon ◽  
...  
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Stellar Populations ◽  
Star Formation History ◽  
Star Forming ◽  
Formation History ◽  
Stellar Masses ◽  
The Universe ◽  
Selection Of

AbstractWe discuss the selection of star-forming galaxies at z≃6 through the Lyman-break technique. Spitzer imaging implies many of these contain older stellar populations (>200Myr) which produce detectable Balmer breaks. The ages and stellar masses (∼1010M⊙) imply that the star formation rate density at earlier epochs may have been significantly higher than at z≃6, and might have played a key role in re-ionizing the universe.

scholarly journals ALMA twenty-six arcmin2 survey of GOODS-S at one millimeter (ASAGAO): Millimeter properties of stellar mass selected galaxies

2020 ◽  
Vol 72 (4) ◽  
Author(s):  
Yuki Yamaguchi ◽  
Kotaro Kohno ◽  
Bunyo Hatsukade ◽  
Tao Wang ◽  
Yuki Yoshimura ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Star Formation Rate ◽  
Signal To Noise Ratio ◽  
Formation Rate ◽  
Stellar Mass ◽  
Star Forming ◽  
Deep Survey ◽  
Stellar Masses ◽  
Relationship Of

Abstract We make use of the ALMA twenty-Six Arcmin2 survey of GOODS-S At One-millimeter (ASAGAO), deep 1.2 mm continuum observations of a 26-arcmin2 region in the Great Observatories Origins Deep Survey-South (GOODS-S) obtained with Atacama Large Millimeter/sub-millimeter Array (ALMA), to probe dust-enshrouded star formation in K-band selected (i.e., stellar mass selected) galaxies, which are drawn from the FourStar Galaxy Evolution Survey (ZFOURGE) catalog. Based on the ASAGAO combined map, which was created by combining ASAGAO and ALMA archival data in the GOODS-South field, we find that 24 ZFOURGE sources have 1.2 mm counterparts with a signal-to-noise ratio >4.5 (1σ ≃ 30–70 μJy beam−1 at 1.2 mm). Their median redshift is estimated to be $z$median = 2.38 ± 0.14. They generally follow the tight relationship of the stellar mass versus star formation rate (i.e., the main sequence of star-forming galaxies). ALMA-detected ZFOURGE sources exhibit systematically larger infrared (IR) excess (IRX ≡ LIR/LUV) compared to ZFOURGE galaxies without ALMA detections even though they have similar redshifts, stellar masses, and star formation rates. This implies the consensus stellar-mass versus IRX relation, which is known to be tight among rest-frame-ultraviolet-selected galaxies, cannot fully predict the ALMA detectability of stellar-mass-selected galaxies. We find that ALMA-detected ZFOURGE sources are the main contributors to the cosmic IR star formation rate density at $z$ = 2–3.

scholarly journals Evolution of star formation rate–density relation over cosmic time in a simulated universe: the observed reversal reproduced

2019 ◽  
Vol 489 (1) ◽  
pp. 339-348 ◽  
Author(s):  
Ho Seong Hwang ◽  
Jihye Shin ◽  
Hyunmi Song
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Local Density ◽  
Formation Rate ◽  
Cosmic Time ◽  
Galaxy Cluster ◽  
Star Forming ◽  
Hydrodynamical Simulation ◽  
Density Relation ◽  
Stellar Masses

ABSTRACT We use the IllustrisTNG cosmological hydrodynamical simulation to study the evolution of star formation rate (SFR)–density relation over cosmic time. We construct several samples of galaxies at different redshifts from z = 2.0 to z = 0.0, which have the same comoving number density. The SFR of galaxies decreases with local density at z = 0.0, but its dependence on local density becomes weaker with redshift. At z ≳ 1.0, the SFR of galaxies increases with local density (reversal of the SFR–density relation), and its dependence becomes stronger with redshift. This change of SFR–density relation with redshift still remains even when fixing the stellar masses of galaxies. The dependence of SFR on the distance to a galaxy cluster also shows a change with redshift in a way similar to the case based on local density, but the reversal happens at a higher redshift, z ∼ 1.5, in clusters. On the other hand, the molecular gas fraction always decreases with local density regardless of redshift at z = 0.0–2.0 even though the dependence becomes weaker when we fix the stellar mass. Our study demonstrates that the observed reversal of the SFR–density relation at z ≳ 1.0 can be successfully reproduced in cosmological simulations. Our results are consistent with the idea that massive, star-forming galaxies are strongly clustered at high redshifts, forming larger structures. These galaxies then consume their gas faster than those in low-density regions through frequent interactions with other galaxies, ending up being quiescent in the local universe.

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