scholarly journals High molecular gas content and star formation rates in local galaxies that host quasars, outflows, and jets

2020 ◽  
Vol 498 (2) ◽  
pp. 1560-1575 ◽  
Author(s):  
M E Jarvis ◽  
C M Harrison ◽  
V Mainieri ◽  
G Calistro Rivera ◽  
P Jethwa ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Gas Content ◽  
Molecular Gas ◽  
Host Galaxies ◽  
Gas Reservoirs ◽  
Galaxy Population ◽  
Stellar Masses ◽  
Gas Fractions

ABSTRACT We use a sample of powerful $z\, \approx \, 0.1$ type 2 quasars (‘obscured’; log [LAGN/erg s$^{-1}]\, \gtrsim \, 45$), which host kpc-scale ionized outflows and jets, to identify possible signatures of AGN feedback on the total molecular gas reservoirs of their host galaxies. Specifically, we present Atacama Pathfinder EXperiment (APEX) observations of the CO(2–1) transition for nine sources and the CO(6–5) for a subset of three. We find that the majority of our sample reside in starburst galaxies (average specific star formation rates – sSFR – of 1.7 Gyr−1), with the seven CO-detected quasars also having large molecular gas reservoirs (average Mgas = 1.3 × 1010 M⊙), even though we had no pre-selection on the star formation or molecular gas properties. Despite the presence of quasars and outflows, we find that the molecular gas fractions (Mgas/M⋆ = 0.1–1.2) and depletion times (Mgas/SFR = 0.16–0.95 Gyr) are consistent with those expected for the overall galaxy population with matched stellar masses and sSFRs. Furthermore, for at least two of the three targets with the required measurements, the CO(6–5)/CO(2–1) emission-line ratios are consistent with star formation dominating the CO excitation over this range of transitions. The targets in our study represent a gas-rich phase of galaxy evolution with simultaneously high levels of star formation and nuclear activity; furthermore, the jets and outflows do not have an immediate appreciable impact on the global molecular gas reservoirs.

scholarly journals Constraining star formation timescales with molecular gas and young star clusters

2019 ◽  
Vol 15 (S352) ◽  
pp. 350-352
Author(s):  
Kathryn Grasha ◽  
Daniela Calzetti
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Star Clusters ◽  
Young Star ◽  
Molecular Gas ◽  
Gas Reservoirs ◽  
Multi Wavelength ◽  
Predictive Theory ◽  
Young Star Clusters ◽  
Co Observations

AbstractStar formation provides insight into the physical processes that govern the transformation of gas into stars. A key missing piece in a predictive theory of star formation is the link between scales of individual stars and star clusters up to entire galaxies. LEGUS is now providing the information to test the overall organization and spatial evolution of star formation. We present our latest findings of using star clusters from LEGUS combined with ALMA CO observations to investigate the transition from molecular gas to star formation in local galaxies. This work paves the way for future JWST observations of the embedded phase of star formation, the last missing ingredient to connect young star clusters and their relation with gas reservoirs. Multi-wavelength studies of local galaxies and their stellar and gas components will help shed light on early phases of galaxy evolution and properties of the ISM at high-z.

scholarly journals Inflow of atomic gas fuelling star formation

2015 ◽  
Vol 11 (A29B) ◽  
pp. 229-230
Author(s):  
M. J. Michałowski ◽  
G. Gentile ◽  
J. Hjorth ◽  
M. R. Krumholz ◽  
N. R. Tanvir ◽  
...  
Keyword(s):  
Star Formation ◽  
Gamma Ray ◽  
Molecular Gas ◽  
Host Galaxies ◽  
Gas Reservoirs ◽  
Gamma Ray Burst ◽  
Gas Cooling ◽  
Low Metallicity ◽  
Atomic Gas ◽  
Compact Array

AbstractGamma-ray burst host galaxies are deficient in molecular gas, and show anomalous metal-poor regions close to GRB positions. Using recent Australia Telescope Compact Array (ATCA) Hi observations we show that they have substantial atomic gas reservoirs. This suggests that star formation in these galaxies may be fuelled by recent inflow of metal-poor atomic gas. While this process is debated, it can happen in low-metallicity gas near the onset of star formation because gas cooling (necessary for star formation) is faster than the Hi-to-H2 conversion.

scholarly journals Lensed quiescent galaxies at z ∼ 2: What quenched their star formation?

2019 ◽  
Vol 15 (S352) ◽  
pp. 281-281
Author(s):  
Allison Man
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Stellar Structure ◽  
Gas Content ◽  
Molecular Gas ◽  
Massive Galaxies ◽  
Quenching Mechanisms ◽  
Multiple Absorption ◽  
Pilot Sample ◽  
Outstanding Issue

AbstractA key outstanding issue in galaxy evolution studies is how galaxies quench their star formation. I will present new results from our VLT/X-Shooter, ALMA and VLA campaign of a pilot sample of lensed quiescent massive galaxies at z > 1.5. Lensing magnification enables us to spatially resolve the stellar structure and kinematics of these compact galaxies, that are otherwise barely resolvable even with HST. Our deep X-Shooter spectra provided multiple absorption lines enabling strong constraints on their stellar populations, namely their star formation rates, ages, dispersions, and in some cases metallicities. Our complementary ALMA+VLA programme probes their molecular gas content through CO emission. All these observations provide unparalleled constraints on their quenching mechanisms. Our results indicate that quiescent galaxies at z ∼ 2 (1) have short star formation timescales of a few hundred Myrs; (2) have a variety of stellar morphology from exponential disks to bulges; (3) are devoid of molecular gas; and (4) host low-luminosity active galactic nuclei which may be responsible for suppressing star formation. In addition to discussing the insights gained on quenching, I will highlight how these findings bring about new questions that can be addressed with future JWST and ALMA studies.

scholarly journals GRB host galaxies: theoretical investigation

2011 ◽  
Vol 7 (S279) ◽  
pp. 353-354
Author(s):  
Jirong Mao
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Galaxy Evolution ◽  
Gamma Ray ◽  
Dark Matter Halo ◽  
Host Galaxy ◽  
Host Galaxies ◽  
X Ray ◽  
Star Forming ◽  
Stellar Masses

AbstractLong gamma-ray bursts (GRBs) can be linked to the massive stars and their host galaxies are assumed to be the star-forming galaxies within small dark matter halos. We apply a galaxy evolution model, in which the star formation process inside the virialized dark matter halo at a given redshift is achieved. The star formation rates (SFRs) in the GRB host galaxies at different redshifts can be derived from our model. The related stellar masses, luminosities, and metalicities of these GRB host galaxies are estimated. We also calculate the X-ray and optical absorption of GRB afterglow emission. At higher redshift, the SFR of host galaxy is stronger, and the absorption in the X-ray and optical bands of GRB afterglow is stronger, when the dust and metal components are locally released, surrounding the GRB environment. These model predictions are compared with some observational data as well.

scholarly journals ALMA reveals large molecular gas reservoirs in recently-quenched galaxies

2019 ◽  
Vol 15 (S352) ◽  
pp. 199-199
Author(s):  
Katherine Suess
Keyword(s):  
Star Formation ◽  
Rapid Quenching ◽  
Molecular Gas ◽  
Gas Reservoirs ◽  
Physical Mechanisms ◽  
Quenching Process ◽  
Star Formation In Galaxies ◽  
Gas Fractions ◽  
The Ideal

AbstractWe still do not understand the physical mechanisms that are responsible for suppressing star formation in galaxies. Observations of post-starburst galaxies, whose spectra indicate that an intense period of star formation was followed by rapid quenching, are the ideal sample to probe the quenching process. We have conducted an ALMA survey of CO(2-1) in 13 of these recently- quenched galaxies at z ∼ 0.7 – high enough redshift that these galaxies likely just concluded their primary epoch of star formation, but low enough redshift for follow-up observations to be feasible. Our observations reveal a stunning diversity of molecular gas properties: despite a uniform optical selection and low apparent SFRs, the detected galaxies span a factor of > 30 in CO luminosity and have inferred gas fractions ranging from < 1% to 20%. These observations indicate that quenching does not require the total removal or depletion of molecular gas. No current models of the quenching process can fully explain our results.

scholarly journals On the Evolutionary Connection Between AGNs and GALEX UV-Excess Early-Type Galaxies

2009 ◽  
Vol 5 (S267) ◽  
pp. 458-458
Author(s):  
Hyun-Jin Bae ◽  
Kiyun Yun ◽  
Yumi Choi ◽  
Suk-Jin Yoon
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Galaxy Evolution ◽  
Galactic Nuclei ◽  
Accurate Information ◽  
Early Type ◽  
Host Galaxies ◽  
Evolutionary Connection ◽  
Uv Excess

The interplay between active galactic nuclei (AGNs) and their host galaxies' star-formation activities is one of the central topics in pursuing an understanding of galaxy evolution. With the advent of the Galaxy Evolution Explorer (GALEX), we have much more accurate information than ever about the recent star formation (RSF) histories of early-type galaxies within ~ 1.5 Gyr in the local universe. Using a subset of ~ 1000 GALEX/SDSS type 2 AGN-host early-type galaxies (E/S0) based on the emission-line ratio diagnosis, we explore how AGNs affect the RSF histories of the early-type hosts and vice versa. In this contribution, we present a preliminary yet interesting result on the intimate connection between AGN activity and the RSF histories of early-type galaxies.

The impact of AGN on the life of their host galaxies at z ∼ 2

2019 ◽  
Vol 15 (S356) ◽  
pp. 194-198
Author(s):  
Chiara Circosta
Keyword(s):  
Star Formation ◽  
Galactic Nuclei ◽  
Molecular Gas ◽  
Host Galaxies ◽  
Gas Reservoir ◽  
Star Forming ◽  
Normal Galaxies ◽  
Two Samples ◽  
Stellar Masses ◽  
The Impact

AbstractFeedback from active galactic nuclei (AGN) is thought to be key in shaping the life cycle of host galaxies by regulating star formation. Therefore, measuring the molecular gas reservoir out of which stars form is essential to understand the impact of AGN on star formation. In this talk I present an ongoing analysis to study the CO(J = 3−2) emission in a sample of 25 AGN at z ∼ 2 using ALMA observations. The CO properties of our AGN have been compared to normal (non-AGN) star-forming galaxies. The comparison between the two samples reveals that, on average, the CO luminosities of AGN at high stellar masses (log(M*/M⊙) > 11) are 0.5 dex lower than normal galaxies. We ascribe this difference to the AGN activity, which could be able to change the conditions of the gas through, e.g., excitation, heating or removal of CO.

scholarly journals Search and analysis of giant radio galaxies with associated nuclei (SAGAN)

2020 ◽  
Vol 643 ◽  
pp. A111
Author(s):  
P. Dabhade ◽  
F. Combes ◽  
P. Salomé ◽  
J. Bagchi ◽  
M. Mahato
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Large Fraction ◽  
Radio Galaxies ◽  
Gas Content ◽  
Molecular Gas ◽  
Disc Galaxy ◽  
Normal Galaxies ◽  
Upper Limits ◽  
Formation Efficiency

Radio galaxies with jets of relativistic particles are usually hosted by massive elliptical galaxies with active nuclei powered by accretion of interstellar matter onto a supermassive black hole. In some rare cases (< 5%), their jets drive the overall structure to sizes larger than 700 kpc, and they are called giant radio galaxies (GRGs). A very small fraction of the population of such radio galaxies contains molecular and atomic gas in the form of rings or discs that can fuel star formation. The origin of this gas is not well known; it has sometimes been associated with a minor merger with a gas-rich disc galaxy (e.g. Centaurus A) or cooling of material from a hot X-ray atmosphere (e.g. cooling flows). The giant radio jets might be the extreme evolution of these objects, and they can teach us about the radio galaxy evolution. We selected 12 targets from a catalogue of 820 GRGs that are likely to be in a gas-accretion and star formation phase. The targets were selected from the mid-infrared to contain heated dust. We report here the results of IRAM-30m observations, the molecular gas content, and the star formation efficiency, and we discuss the origin of the gas and disc morphology. Three out of our 12 targets are detected, and for the others, we report significant upper limits. We combine our three detections and upper limits with four additional detected GRGs from the literature to discuss the results. Most of the GRG targets belong to the main sequence, and a large fraction are in the passive domain. Their star formation efficiency is comparable to normal galaxies, except for two galaxies that are deficient in molecular gas with a short (∼200 Myr) depletion time, and a quiescent gas-rich giant spiral galaxy. In general, the depletion time is much longer than the lifetime of the giant radio jet.

scholarly journals X-Ray Selected Type 2 QSOs and Their Host Galaxies

2009 ◽  
Vol 5 (S267) ◽  
pp. 80-84
Author(s):  
Vincenzo Mainieri ◽  
Keyword(s):  
Star Formation ◽  
Selection Criteria ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Host Galaxies ◽  
X Ray ◽  
Massive Galaxies ◽  
Stellar Masses ◽  
Best Fit

AbstractWe present a large sample of X-ray selected type 2 QSOs from the XMM–COSMOS survey. Type 2 QSOs are luminous AGN whose central engines are obscured by large amounts of gas and dust. The selection criteria we have used are based on high X-ray luminosity (LX > 1044 erg s−1) and heavy obscuration (NH > 1022 cm−2). We derived stellar masses and star-formation rate estimates for the host galaxies from the best fit of the observed photometry. Type 2 QSOs are generally hosted in massive galaxies with on-going star formation.

scholarly journals Gas fractions and depletion times in galaxies with different degrees of interaction

2020 ◽  
Vol 635 ◽  
pp. A197 ◽  
Author(s):  
S. Díaz-García ◽  
J. H. Knapen
Keyword(s):  
Star Formation ◽  
Mass Concentration ◽  
Control Sample ◽  
Far Infrared ◽  
Stellar Mass ◽  
Interacting Galaxies ◽  
Gas Content ◽  
Galaxy Mergers ◽  
Stellar Masses ◽  
Gas Fractions

Context. A moderate enhancement of the star formation rates (SFR) in local interacting galaxies has been reported, but the physical mechanisms leading to this increase are not clear. Aims. We study the atomic gas content and the central stellar mass concentration for a sample of almost 1500 nearby galaxies to further investigate the nature of starbursts and the influence of galaxy-galaxy interactions on star formation. Methods. We used a sample of catalogued interacting and non-interacting galaxies in the S4G survey – along with archival H I gas masses, stellar masses (M*), and SFRs from IRAS far-infrared fluxes – and calculate depletion times (τ) and gas fractions. We traced the central stellar mass concentration from the inner slope of the stellar component of the rotation curves, dRv*(0). Starbursts are defined as galaxies with a factor > 4 enhanced SFR relative to a control sample of non-interacting galaxies which are ±0.2 dex in stellar mass and ±1 in T-type. Results. Starbursts are mainly early-type (T ≲ 5), massive spiral galaxies (M* ≳ 1010 M⊙) that are not necessarily interacting. For a given stellar mass bin, starbursts are characterised by lower gas depletion times, similar gas fractions, and larger central stellar mass concentrations than non-starburst galaxies. The global distributions of gas fraction and gas depletion time of interacting galaxies are not statistically different from those of their non-interacting counterparts. However, in the case of currently merging galaxies, the median gas depletion time is a factor of 0.4 ± 0.2 that of control sample galaxies, and their SFRs are a factor of 1.9 ± 0.5 enhanced, even though the median gas fraction is similar. Conclusions. Starbursts present long-lasting star formation in circumnuclear regions, which causes an enhancement of the central stellar density at z ≈ 0 in both interacting and non-interacting systems. Starbursts have low gas depletion timescales, yet similar gas fractions as normal main-sequence galaxies. Galaxy mergers cause a moderate enhancement of the star formation efficiency.

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