VARIATIONS IN THE STAR FORMATION EFFICIENCY OF THE DENSE MOLECULAR GAS ACROSS THE DISKS OF STAR-FORMING GALAXIES

ABSTRACT We study the presence of optically-selected active galactic nuclei (AGNs) within a sample of 867 galaxies extracted from the extended Calar-Alto Legacy Integral Field spectroscopy Area (eCALIFA) spanning all morphological classes. We identify 10 Type-I and 24 Type-II AGNs, amounting to ∼4 per cent of our sample, similar to the fraction reported by previous explorations in the same redshift range. We compare the integrated properties of the ionized and molecular gas, and stellar population of AGN hosts and their non-active counterparts, combining them with morphological information. The AGN hosts are found in transitory parts (i.e. green-valley) in almost all analysed properties which present bimodal distributions (i.e. a region where reside star-forming galaxies and another with quiescent/retired ones). Regarding morphology, we find AGN hosts among the most massive galaxies, with enhanced central stellar-mass surface density in comparison to the average population at each morphological type. Moreover, their distribution peaks at the Sab-Sb classes and none are found among very late-type galaxies (>Scd). Finally, we inspect how the AGN could act in their hosts regarding the quenching of star-formation. The main role of the AGN in the quenching process appears to be the removal (or heating) of molecular gas, rather than an additional suppression of the already observed decrease of the star-formation efficiency from late-to-early type galaxies.

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/202039005 ◽

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.

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Abundant molecular gas and inefficient SF in intra-cluster regions of a ram pressure stripped tail

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314009740 ◽

2014 ◽

Vol 10 (S309) ◽

pp. 227-229

Author(s):

P. Jáchym ◽

M. Sun ◽

F. Combes ◽

L. Cortese ◽

J. D. P. Kenney

Keyword(s):

Star Formation ◽

Molecular Gas ◽

X Ray ◽

Star Forming ◽

Ram Pressure ◽

Formation Efficiency ◽

First Time

AbstractFor the first time in any ram pressure stripped galaxy, we detect large amounts of cold molecular gas in the X-ray bright, and star forming tail of ESO 137-001 in the Norma cluster. We find very low star formation efficiency in the stripped gas, similar to values found in the outer spiral disks where however molecular gas is mostly undetected. The results were recently published in Jáchym et al. (2014).

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DYNAMO: An upclose view of turbulent, clumpy galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320001301 ◽

2019 ◽

Vol 15 (S352) ◽

pp. 317-317

Author(s):

Deanne Fisher

Keyword(s):

Star Formation ◽

Main Sequence ◽

Velocity Dispersion ◽

Molecular Gas ◽

Rotating Disks ◽

Giant Star ◽

Star Forming ◽

Nearby Galaxies ◽

Formation Efficiency ◽

The Universe

AbstractOver 2/3 of all star formation in the Universe occurs in gas-rich, super-high pressure clumpy galaxies in the epoch of redshift z ∼ 1 – 3. However, because these galaxies are so distant we are limited in the information available to study the properties of star formation and gas in these systems. I will present results using a sample of extremely rare, nearby galaxies (called DYNAMO) that are very well matched in gas fraction (fgas ∼ 20 – 80%), kinematics (rotating disks with velocity dispersions ranging 20 – 100 km/s), structure (exponential disks) and morphology (clumpy star formation) to high-z main-sequence galaxies. We therefore use DYNAMO galaxies as laboratories to study the processes inside galaxies in the dominate mode of star formation in the Universe. In this talk I will report on results from our programs with HST, ALMA, Keck, and NOEMA for DYNAMO galaxies that are aimed at testing models of star formation. We have discovered of an inverse relationship between gas velocity dispersion and molecular gas depletion time. This correlation is directly predicted by theories of feedback-regulated star formation; conversely, predictions of models in which turbulence is driven by gravity only are not consistent with our data. I will also show that feedback-regulated star formation can explain the redshift evolution of galaxy star formation efficiency. I will also present results from a recently acquired map of CO(2-1) in a clumpy galaxy with resolution less than 200 pc. With maps such as these we can begin to study these super giant star forming clumps at scales that are more comparable to local surveys. I will show results for the star formation efficiency of clumps, the boundedness of clumps of molecular gas, and discuss links between star formation efficiency and formation of clumps of stellar mass. The details of clumpy systems are a direct constraint of the results of simulations, especially on the nature of feedback in the high density environments of star formation that dominate the early Universe.

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New emerging results on molecular gas, stars, and dust at z ~ 2, as revealed by low star formation rate and low stellar mass star-forming galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315009874 ◽

2015 ◽

Vol 11 (S319) ◽

pp. 88-91

Author(s):

Miroslava Dessauges-Zavadsky ◽

Michel Zamojski ◽

Daniel Schaerer ◽

Françoise Combes ◽

Eiichi Egami ◽

...

Keyword(s):

Star Formation ◽

High Redshift ◽

Formation Rate ◽

Molecular Gas ◽

Mass Star ◽

Single Star ◽

Massive Galaxies ◽

Star Forming ◽

Formation Efficiency ◽

Gas Ratio

AbstractRecent CO surveys of star-forming galaxies (SFGs) at z ~ 2 have revolutionized our picture of massive galaxies. It is time to expand these studies toward the more common z ~ 2 SFGs with SFR < 40 M⊙ yr−1 and M* < 2.5 × 1010 M⊙. We have derived molecular gas, stars, and dust in 8 such lensed SFGs. They extend the LIR–L'CO(1-0) distribution of massive z>1 SFGs and increase the spread of the SFG star formation efficiency (SFE). A single star formation relation is found when combining all existing CO-detected galaxies. Our low-M* SFGs also reveal a SFE decrease with M* as found locally. A rise of the molecular gas fraction (fgas) with redshift is observed up to z ~ 1.6, but it severely flattens toward higher redshifts. We provide the first insight into the fgas upturn at the low-M* end 109.4 < M*/M⊙ < 1010 reaching fgas ~ 0.7, it is followed by a fgas decrease toward higher M*. Finally, we find a non-universal dust-to-gas ratio among local and high-redshift SFGs and starbursts with near-solar metallicities.

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Molecular gas content in typical L* galaxies at z ∼ 1.5 − 3

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314009880 ◽

2014 ◽

Vol 10 (S309) ◽

pp. 285-286

Author(s):

Miroslava Dessauges-Zavadsky ◽

Michel Zamojski ◽

Daniel Schaerer ◽

Françoise Combes ◽

Eiichi Egami ◽

...

Keyword(s):

Star Formation ◽

Formation Rate ◽

Stellar Mass ◽

Gas Content ◽

Physical Parameters ◽

Molecular Gas ◽

Star Forming ◽

Large Spread ◽

Gas Measurements ◽

Formation Efficiency

AbstractTo extend the molecular gas measurements to typical L* star-forming galaxies (SFGs) at z ∼ 1.5 − 3, we have observed CO emission for five strongly-lensed galaxies selected from the Herschel Lensing Survey. The combined sample of our L* SFGs with CO-detected SFGs at z >1 from the literature shows a large spread in star formation efficiency (SFE). We find that this spread in SFE is due to variations of several physical parameters, primarily the specific star formation rate, but also stellar mass and redshift. An increase of the molecular gas fraction (fgas) is observed from z ∼ 0.2 to z ∼ 1.2, followed by a quasi non-evolution toward higher redshifts, as found in earlier studies. We provide the first measure of fgas of z >1 SFGs at the low-stellar mass end between 109.4 < M∗/M⊙ < 109.9, which shows a clear fgas upturn.

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The ALMaQUEST survey – III. Scatter in the resolved star-forming main sequence is primarily due to variations in star formation efficiency

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slz179 ◽

2020 ◽

Vol 493 (1) ◽

pp. L39-L43 ◽

Cited By ~ 11

Author(s):

Sara L Ellison ◽

Mallory D Thorp ◽

Lihwai Lin ◽

Hsi-An Pan ◽

Asa F L Bluck ◽

...

Keyword(s):

Star Formation ◽

Surface Density ◽

Main Sequence ◽

Star Formation Rate ◽

Formation Rate ◽

Molecular Gas ◽

Star Forming ◽

The Absolute ◽

Correlation Statistics ◽

Formation Efficiency

ABSTRACT Using a sample of 11 478 spaxels in 34 galaxies with molecular gas, star formation, and stellar maps taken from the ALMA-MaNGA QUEnching and STar formation (ALMaQUEST) survey, we investigate the parameters that correlate with variations in star formation rates on kpc scales. We use a combination of correlation statistics and an artificial neural network to quantify the parameters that drive both the absolute star formation rate surface density (ΣSFR), as well as its scatter around the resolved star-forming main sequence (ΔΣSFR). We find that ΣSFR is primarily regulated by molecular gas surface density ($\Sigma _{\rm H_2}$) with a secondary dependence on stellar mass surface density (Σ⋆), as expected from an ‘extended Kennicutt–Schmidt relation’. However, ΔΣSFR is driven primarily by changes in star formation efficiency (SFE), with variations in gas fraction playing a secondary role. Taken together, our results demonstrate that whilst the absolute rate of star formation is primarily set by the amount of molecular gas, the variation of star formation rate above and below the resolved star-forming main sequence (on kpc scales) is primarily due to changes in SFE.

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Resolved star formation relations at high redshift from the IRAM PHIBSS program

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316007833 ◽

2015 ◽

Vol 11 (S315) ◽

Author(s):

Jonathan Freundlich ◽

Françoise Combes ◽

Linda Tacconi ◽

Michael Cooper ◽

Reinhard Genzel ◽

...

Keyword(s):

Star Formation ◽

High Redshift ◽

Formation Rate ◽

Molecular Gas ◽

Formation Processes ◽

Massive Galaxies ◽

Star Forming ◽

Star Forming Regions ◽

Order Of Magnitude ◽

Formation Efficiency

AbstractObserved massive galaxies in the distant Universe form stars at much higher rates than today. High levels of star formation are sustained by a continuous supply of fresh gas and high molecular gas fractions. But after a peak around redshift z=2-3, the star formation rate decreases by an order of magnitude. Is this evolution mostly driven by the available cold gas reservoir, or are the star formation processes qualitatively different near the star formation peak? The Kennicutt-Schmidt relation enables to characterize the star formation efficiency at low and high redshift, but resolved measurements at the scale of the star-forming regions themselves are still challenging at high redshift. Molecular gas observations carried out at the IRAM Plateau de Bure interferometer within the PHIBSS program (Tacconi, Combes et al.) permit us to study the star formation efficiency at sub-galactic scales around z=1.2 and 1.5 for a limited sample of galaxies, and thus help characterize the star formation processes at this epoch. Our results lay in the continuation of the resolved low-redshift measurements, but further studies would be necessary to complement our sample and validate our conclusions.

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The ALMaQUEST Survey: V. The non-universality of kpc-scale star formation relations and the factors that drive them

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3822 ◽

2020 ◽

Author(s):

Sara L Ellison ◽

Lihwai Lin ◽

Mallory D Thorp ◽

Hsi-An Pan ◽

Jillian M Scudder ◽

...

Keyword(s):

Star Formation ◽

Main Sequence ◽

Correlation Coefficients ◽

Molecular Gas ◽

Star Forming ◽

Global Properties ◽

Gas Main ◽

The Galaxy ◽

Data Points ◽

Formation Efficiency

Abstract Using a sample of ∼15,000 kpc-scale star-forming spaxels in 28 galaxies drawn from the ALMA-MaNGA QUEnching and STar formation (ALMaQUEST) survey, we investigate the galaxy-to-galaxy variation of the ‘resolved’ Schmidt-Kennicutt relation (rSK; $\Sigma _{\rm H_2}$ - ΣSFR), the ‘resolved’ star forming main sequence (rSFMS; Σ⋆ - ΣSFR) and the ‘resolved’ molecular gas main sequence (rMGMS; Σ⋆ - $\Sigma _{\rm H_2}$). The rSK relation, rSFMS and rMGMS all show significant galaxy-to-galaxy variation in both shape and normalization, indicating that none of these relations is universal between galaxies. The rSFMS shows the largest galaxy-to-galaxy variation and the rMGMS the least. By defining an ‘offset’ from the average relations, we compute a ΔrSK, ΔrSFMS, ΔrMGMS for each galaxy, to investigate correlations with global properties. We find the following correlations with at least 2σ significance: the rSK is lower (i.e. lower star formation efficiency) in galaxies with higher M⋆, larger Sersic index and lower specific SFR (sSFR); the rSFMS is lower (i.e. lower sSFR) in galaxies with higher M⋆ and larger Sersic index; the rMGMS is lower (i.e. lower gas fraction) in galaxies with lower sSFR. In the ensemble of all 15,000 data points, the rSK relation and rMGMS show equally tight scatters and strong correlation coefficients, compared with a larger scatter and weaker correlation in the rSFMS. Moreover, whilst there is no correlation between ΔrSK and ΔrMGMS in the sample, the offset of a galaxy’s rSFMS does correlate with both of the other two offsets. Our results therefore indicate that the rSK and rMGMS are independent relations, whereas the rSFMS is a result of their combination.

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From global to local scales in galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320001568 ◽

2020 ◽

Vol 15 (S359) ◽

pp. 391-395

Author(s):

Sebastian F. Sánchez ◽

Carlos Lopez Cobá

Keyword(s):

Star Formation ◽

Spatial Scales ◽

Bimodal Distribution ◽

Spectroscopic Properties ◽

Molecular Gas ◽

Ionized Gas ◽

Galaxy Surveys ◽

Quenching Process ◽

Formation Efficiency ◽

Integral Field

AbstractWe summarize here some of the results reviewed recently by Sanchez (2020) comprising the advances in the comprehension of galaxies in the nearby universe based on integral field spectroscopic galaxy surveys. In particular we explore the bimodal distribution of galaxies in terms of the properties of their ionized gas, showing the connection between the star-formation (quenching) process with the presence (absence) of molecular gas and the star-formation efficiency. We show two galaxy examples that illustrates the well known fact that ionization in galaxies (and the processes that produce it), does not happen monolitically at galactic scales. This highlight the importance to explore the spectroscopic properties of galaxies and the evolutionary processes unveiled by them at different spatial scales, from sub-kpc to galaxy wide.

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