scholarly journals Massive galaxies on the road to quenching: ALMA observations of powerful high redshift radio galaxies

2019 ◽  
Vol 621 ◽  
pp. A27 ◽  
Author(s):  
Theresa Falkendal ◽  
Carlos De Breuck ◽  
Matthew D. Lehnert ◽  
Guillaume Drouart ◽  
Joël Vernet ◽  
...  
Keyword(s):  
Star Formation ◽  
Dust Emission ◽  
Radio Galaxies ◽  
Band 3 ◽  
Continuum Emission ◽  
Synchrotron Emission ◽  
Host Galaxies ◽  
Massive Galaxies ◽  
Radio Jets ◽  
Order Of Magnitude

We present 0.″3 (band 6) and 1.″5 (band 3) ALMA observations of the (sub)millimeter dust continuum emission for 25 radio galaxies at 1 <  z <  5.2. Our survey reaches a rms flux density of ∼50 μJy in band 6 (200–250 GHz) and ∼20 μJy in band 3 (100–130 GHz). This is an order of magnitude deeper than single-dish 850 μm observations, and reaches fluxes where synchrotron and thermal dust emission are expected to be of the same order of magnitude. Combining our sensitive ALMA observations with low-resolution radio data from ATCA, higher resolution VLA data, and infrared photometry from Herschel and Spitzer, we have disentangled the synchrotron and thermal dust emission. We determine the star-formation rates and AGN infrared luminosities using our newly developed Multi-resolution and multi-object/origin spectral energy distribution fitting code (MR-MOOSE). We find that synchrotron emission contributes substantially at λ ∼ 1 mm. Through our sensitive flux limits and accounting for a contribution from synchrotron emission in the mm, we revise downward the median star-formation rate by a factor of seven compared to previous estimates based solely on Herschel and Spitzer data. The hosts of these radio-loud AGN appear predominantly below the main sequence of star-forming galaxies, indicating that the star formation in many of the host galaxies has been quenched. Future growth of the host galaxies without substantial black hole mass growth will be needed to bring these objects on the local relation between the supermassive black holes and their host galaxies. Given the mismatch in the timescales of any star formation that took place in the host galaxies and lifetime of the AGN, we hypothesize that a key role is played by star formation in depleting the gas before the action of the powerful radio jets quickly drives out the remaining gas. This positive feedback loop of efficient star formation rapidly consuming the gas coupled to the action of the radio jets in removing the residual gas is how massive galaxies are rapidly quenched.

The diagnostic power of radio spectra from star-forming galaxies

2019 ◽  
Vol 15 (S341) ◽  
pp. 177-186
Author(s):  
Eric J. Murphy
Keyword(s):  
Star Formation ◽  
Dust Emission ◽  
Cosmic Ray ◽  
Microwave Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
H Ii Regions ◽  
Synchrotron Emission ◽  
Very Large Array ◽  
Star Forming

AbstractRadio continuum emission from galaxies is powered by a combination of distinct physical processes, each providing unique diagnostic information. Over frequencies spanning ∼ 1–120 GHz, radio spectra of star-forming galaxies are primarily comprised of: (1) non-thermal synchrotron emission powered by accelerated cosmic-ray electrons/positrons; (2) free-free emission from young massive star-forming (H ii) regions; (3) anomalous microwave emission, which is a dominant, but completely unconstrained, foreground in cosmic microwave background experiments; and (4) cold, thermal dust emission that accounts for most of the dust and total mass content in the interstellar medium in galaxies. In this proceeding, we discuss these key energetic processes that contribute to the radio emission from star-forming galaxies, with an emphasis on frequencies ≳30 GHz, where current investigations of star formation within nearby galaxies show that the free-free emission begins to dominate over non-thermal synchrotron emission. We also discuss how planned radio facilities that will access these frequencies, such as a next-generation Very Large Array (ngVLA), will be transformative to our understanding of the star formation process in galaxies.

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.

scholarly journals Evolution of the dust emission of massive galaxies up toz= 4 and constraints on their dominant mode of star formation

2015 ◽  
Vol 573 ◽  
pp. A113 ◽  
Author(s):  
Matthieu Béthermin ◽  
Emanuele Daddi ◽  
Georgios Magdis ◽  
Claudia Lagos ◽  
Mark Sargent ◽  
...  
Keyword(s):  
Star Formation ◽  
Dust Emission ◽  
Dominant Mode ◽  
Massive Galaxies

scholarly journals Metallicity of the high-redshift Universe traced by radio galaxies

2009 ◽  
Vol 5 (S265) ◽  
pp. 179-180
Author(s):  
K. Matsuoka ◽  
T. Nagao ◽  
R. Maiolino ◽  
A. Marconi ◽  
Y. Taniguchi
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Radio Galaxies ◽  
Narrow Line ◽  
Line Flux ◽  
Model Calculations ◽  
Massive Galaxies ◽  
High Redshift Universe ◽  
Photoionization Model ◽  
Very High

AbstractWe investigate the metallicity of the narrow line regions (NLRs) of high-z radio galaxies (HzRGs), using new deep optical spectra of 9 HzRGs obtained with FORS2 on VLT and data from the literature. To estimate the metallicity of NLRs we focus on the Civ/Heii and Ciii]/Civ flux ratios. Based on comparison between the observed emission-line flux ratios and the prediction of our photoionization model calculations, we find no significant metallicity evolution in NLRs of HzRGs, up to z ~ 4. We discuss the possibility that massive galaxies had almost completed the major epoch of the star formation in the very high-z universe (z > 5).

scholarly journals New submillimeter diagnostics of physical properties of ISM in high redshift galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 430-430
Author(s):  
Yoichi Tamura ◽  
Kouichiro Nakanishi ◽  
Kotaro Kohno ◽  
Ryohei Kawabe
Keyword(s):  
Star Formation ◽  
Physical Properties ◽  
High Redshift ◽  
Formation Rate ◽  
Host Galaxies ◽  
Power Sources ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Order Of Magnitude ◽  
New Diagnosis

AbstractWe present a new diagnosis method for determining physical properties of star-forming gas in high-z galaxies. In this method, we employed three key observational quantities, [CI], CO, and FIR luminosities, including our new detections of CO J = 4–3 emission from the pure-starburst (non-AGN) submm galaxy SMM J14011+0252 (z = 2.6) and the type-2 AGN IRAS FSC 10214+4724 (z = 2.3) obtained with the Nobeyama Millimeter Array (NMA) at the Nobeyama Radio Observatory. These two sources have extremely high star formation rate, and exhibit strong emission of CO and [CI] 609 μm lines. We determined ISM physical conditions for the two objects and another three high-z quasars in order to investigate the relationship between their ISM and power sources (i.e., massive star formation or AGN). A new PDR analysis (Wolfire et al. 2005, private communication) using CO, [CI], and FIR on five high-z sources provides new evidence that AGN host galaxies harbor denser (log nH ~ 5–6) ISM exposed to stronger far-UV fluxes of log G0 ~ 3.5–4 than the non-AGN submm galaxy. Volume filling factors of the star-forming dense gas in the AGN hosts are an order of magnitude smaller than that of the pure-starburst submm galaxy. This suggests that, in these AGN hosts, dense molecular clouds are dominating the central kpc around AGN, triggering extensive circumnuclear starbursts, and possibly feeding their central supermassive black hole simultaneously.

scholarly journals Molecular Gas in Galaxies at all Redshifts

2010 ◽  
Vol 6 (S277) ◽  
pp. 47-54
Author(s):  
Françoise Combes
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Star Formation History ◽  
Gas Content ◽  
Continuum Emission ◽  
Massive Galaxies ◽  
Normal Galaxies ◽  
Galaxy Type ◽  
Formation History ◽  
Formation Efficiency

AbstractI review some recent results about the molecular content of galaxies, obtained essentially from the CO lines, but also dense tracers, or the dust continuum emission. New results have been obtained on molecular cloud physics, and their efficiency to form stars, shedding light on the Kennicutt-Schmidt law as a function of surface density and galaxy type. Large progress has been made on galaxy at moderate and high redshifts, allowing to interprete the star formation history and star formation efficiency as a function of gas content, or galaxy evolution. In massive galaxies, the gas fraction was higher in the past, and galaxy disks were more unstable and more turbulent. ALMA observations will allow the study of more normal galaxies at high z with higher spatial resolution and sensitivity.

scholarly journals Quasar Metal Abundances & Host Galaxy Evolution

2009 ◽  
Vol 5 (S265) ◽  
pp. 171-178
Author(s):  
Fred Hamann ◽  
Leah E. Simon
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
High Redshift ◽  
Big Bang ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Massive Galaxies ◽  
Central Regions ◽  
Metal Abundances ◽  
The Big Bang

AbstractHigh-redshift quasars provide a unique glimpse into the early evolution of massive galaxies. The physical processes that trigger major bursts of star formation in quasar host galaxies (mergers and interactions) probably also funnel gas into the central regions to grow the super-massive black holes (SMBHs) and ignite the luminous quasar phenomenon. The globally dense environments where this occurs were probably also among the first to collapse and manufacture stars in significant numbers after the big bang. Measurements of the elemental abundances near quasars place important constraints on the nature, timing and extent of this star formation. A variety of studies using independent emission and absorption line diagnostics have shown that quasar environments have gas-phase metallicities that are typically a few times solar at all observed redshifts. These results are consistent with galaxy evolution scenarios in which large amounts of star formation (e.g., in the central regions) precede the visibly bright quasar phase. An observed trend for higher metallicities in more luminmous quasars (powered by more massive SMBHs) is probably tied to the well-known mass–metallicity relation among ordinary galaxies. This correlation and the absence of a trend with redshift indicate that mass is a more important parameter in the evolution than the time elapsed since the big bang.

scholarly journals Discovery of a Protocluster Core Associated with an Enormous Lya Nebula at z = 2.3

2021 ◽  
Vol 922 (2) ◽  
pp. 236
Author(s):  
Qiong Li ◽  
Ran Wang ◽  
Helmut Dannerbauer ◽  
Zheng Cai ◽  
Bjorn Emonts ◽  
...  
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
Line Emission ◽  
Peak Position ◽  
The Other ◽  
Line Ratio ◽  
Continuum Emission ◽  
Mass Estimation ◽  
Massive Galaxies

Abstract The MAMMOTH-1 nebula at z = 2.317 is an enormous Lyα nebula (ELAN) extending to a ∼440 kpc scale at the center of the extreme galaxy overdensity BOSS 1441. In this paper, we present observations of the CO(3 − 2) and 250 GHz dust-continuum emission from MAMMOTH-1 using the IRAM NOrthern Extended Millimeter Array. Our observations show that CO(3 − 2) emission in this ELAN has not extended widespread emission into the circum- and inter-galactic media. We also find a remarkable concentration of six massive galaxies in CO(3 − 2) emission in the central ∼100 kpc region of the ELAN. Their velocity dispersions suggest a total halo mass of M 200c ∼ 1013.1 M ⊙, marking a possible protocluster core associated with the ELAN. The peak position of the CO(3 − 2) line emission from the obscured AGN is consistent with the location of the intensity peak of MAMMOTH-1 in the rest-frame UV band. Its luminosity line ratio between the CO(3 − 2) and CO(1 − 0)r 3,1 is 0.61 ± 0.17. The other five galaxies have CO(3 − 2) luminosities in the range of (2.1–7.1) × 109 K km s−1 pc2, with the star-formation rates derived from the 250 GHz continuum of (<36)–224 M ⊙ yr−1. Follow-up spectroscopic observations will further confirm more member galaxies and improve the accuracy of the halo mass estimation.

scholarly journals On the Environments of Giant Radio Galaxies

2021 ◽  
Author(s):  
Ting-Wen Lan ◽  
J Xavier Prochaska
Keyword(s):  
Large Scale ◽  
Radio Galaxies ◽  
Sloan Digital Sky Survey ◽  
Host Galaxies ◽  
Homogeneous Sample ◽  
Large Scale Structures ◽  
Radio Jets ◽  
Sky Survey ◽  
Scale Structures ◽  
Control Samples

Abstract We test the hypothesis that environments play a key role in enabling the growth of enormous radio structures spanning more than 700 kpc, an extreme population of radio galaxies called giant radio galaxies (GRGs). To achieve this, we explore (1) the relationships between the occurrence of GRGs and the surface number density of surrounding galaxies, including satellite galaxies and galaxies from neighboring halos, as well as (2) the GRG locations towards large-scale structures. The analysis is done by making use of a homogeneous sample of 110 GRGs detected from the LOFAR Two-metre Sky Survey in combination with photometric galaxies from the DESI Legacy Imaging Surveys and a large-scale filament catalog from the Sloan Digital Sky Survey. Our results show that the properties of galaxies around GRGs are similar with that around the two control samples, consisting of galaxies with optical colors and luminosity matched to the properties of the GRG host galaxies. Additionally, the properties of surrounding galaxies depend on neither their relative positions to the radio jet/lobe structures nor the sizes of GRGs. We also find that the locations of GRGs and the control samples with respect to the nearby large-scale structures are consistent with each other. These results demonstrate that there is no correlation between the GRG properties and their environments traced by stars, indicating that external galaxy environments are not the primary cause of the large sizes of the radio structures. Finally, regarding radio feedback, we show that the fraction of blue satellites does not correlate with the GRG properties, suggesting that the current epoch of radio jets have minimal influence on the nature of their surrounding galaxies.

scholarly journals Dense molecular clouds and associated star formation in the Magellanic Clouds

2006 ◽  
Vol 2 (S237) ◽  
pp. 40-46
Author(s):  
Mónica Rubio
Keyword(s):  
Star Formation ◽  
Uv Radiation ◽  
Molecular Clouds ◽  
Massive Star ◽  
Dust Emission ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Giant Molecular Clouds ◽  
Stellar Objects ◽  
Ir Sources

AbstractMultiwavelengths studies of massive star formation regions in the LMC and SMC reveal that a second generation of stars is being formed in dense molecular clouds located in the surroundings of the massive clusters. These dense molecular clouds have survived the action of massive star UV radiation fields and winds and they appear as compact dense H2 knots in regions of weak CO emission. Alternatively, we have found that large molecular clouds, probably remnants of the parental giant molecular clouds where the first generation of stars were formed, are suffering the interaction of the winds and UV radiation field in their surfaces in the direction of the central massive cluster or massive stars. These molecular regions show 1.2 mm continuum emission form cold dust and they show embedded IR sources as determined from deep ground base JHKs imaging. The distribution of young IR sources as determined from their Mid IR colors obtained by SPITZER concentrate in the maxima of CO and dust emission. IR spectroscopy of the embedded sources with high IR excess confirm their nature as massive young stellar objects (MYSO's). Our results are suggestive of contagious star formation where triggering and induced star formation could be taking place.

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