Molecular gas and star formation in the SAURON early-type galaxies

By F. Combes, L. M. Young, M. Bureau. 2007

169 citations recorded by the source corpus.

We present the results of a survey of CO emission in 43 of the 48 representative E/S0 galaxies observed in the optical with the SAURON integral-field spectrograph. The CO detection rate is 12/43 or 28 per cent. This is lower than previous studies of early-types but can probably be attributed to different sample selection criteria. As expected, earlier type, more luminous and massive galaxies have a relatively lower molecular gas content. We find that CO-rich galaxies tend to have higher Hβ but lower Fe5015 and Mgb absorption indices than CO-poor galaxies. Those trends appear primarily driven by the age of the stars, a hypothesis supported by the fact that the galaxies with the strongest evidence of star formation are also the most CO-rich. In fact, the early-type galaxies from the current sample appear to extend the well-known correlations between far-infrared (FIR) luminosity, dust mass and molecular mass of other galaxy types. The star formation interpretation is also consistent with the SAURON galaxies' radio continuum and FIR flux ratios, and their inferred star formation efficiencies are similar to those in spiral galaxies. It thus appears that we have identified the material fueling (residual) star formation in early-type galaxies, and have demonstrated that it is actively being transformed. Nevertheless, the lack of strong correlations between the CO content and most stellar parameters is compatible with the idea that, in a significant number of sample galaxies, the molecular gas has been accreted from the outside and has properties rather independent from the old, pre-existing stellar component.

Subfields: Astronomy and Astrophysics, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/9ce2040e281a4040b314cf8ae531b888b10a25d5

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In Astronomy and Astrophysics

1. M. Cappellari
2. P. Hopkins
3. T. Naab
4. L. Hernquist
5. A. Dekel
6. C. Conroy
7. R. Dav'e
8. R. Somerville

In Global and Planetary Change

1. T. Naab
2. M. Cappellari
3. R. Dav'e
4. T. Heckman
5. Romain Teyssier
6. Cheng Li
7. G. Kauffmann
8. Mark R. Krumholz

Citations in the corpus

• Star Formation in the Milky Way and Nearby Galaxies (2012, background): “…of these galaxies reveals significant detections of molecular gas in a large fraction of the galaxies with detected star formation, with molecular gas masses of 107− 1010M⊙ (Combes et al. 2007; Crocker et al. 2011), and with SFRs roughly consistent with the Schmidt law seen in normal galaxies.”
• xCOLD GASS: The Complete IRAM 30 m Legacy Survey of Molecular Gas for Galaxy Evolution Studies (2017, background): “…spiral galaxies (Braine et al. 1993; Sage 1993), cluster spiral galaxies (Kenney & Young 1988; Boselli et al. 1997), early-type galaxies (Combes et al. 2007; Krips et al. 2010; Young et al. 2011), galaxies with active nuclei (Helfer & Blitz 1993; Sakamoto et al. 1999; Garćıa-Burillo et…”
• DISCOVERY OF AN ACTIVE GALACTIC NUCLEUS DRIVEN MOLECULAR OUTFLOW IN THE LOCAL EARLY-TYPE GALAXY NGC 1266 (2011, methodology): “If we assume that all of the far-infrared (FIR) luminosity (7 × 1043 erg s−1; Gil de Paz et al. 2007; Combes et al. 2007) is from star formation (an upper limit since the nucleus of NGC 1266 contains an AGN), we calculate a global obscured SFRFIR of 2.2 M⊙ yr −1 using Kennicutt (1998),…”
• COLD GASS, an IRAM legacy survey of molecular gas in massive galaxies – I. Relations between H2, H i, stellar content and structural properties (2011, background): “Molecular gas has been detected in early-type galaxies (e.g. in the SAURON sample, Combes et al. 2007), but at levels even below this limit.”
• From star clusters to dwarf galaxies: the properties of dynamically hot stellar systems (2008, background): “However, considering the results by Combes et al. (2007), the mass of the gas is probably indeed negligible for their sample of galaxies.”
• Observational evidence for AGN feedback in early-type galaxies (2007, background): “…lenticular galaxies has shown that many of them have (often extended) emission lines and signs of recent star formation as well as CO emissions from molecular gas and atomic hydrogen indicating sometimes substantial reservoirs of gas (Sarzi et al. 2006; Morganti et al. 2006; Combes et al. 2007).”
• THE HERSCHEL REFERENCE SURVEY: DUST IN EARLY-TYPE GALAXIES AND ACROSS THE HUBBLE SEQUENCE (2011, background): “Wrobel & Heeschen (1988), and more recently Combes et al. (2007) and Lucero & Young (2007), have found similar values of q for ETGs in which star formation is occurring.”
• The ATLAS3D project – IV. The molecular gas content of early-type galaxies (2011, methodology): “Data sources: 1 = this paper, 2 = Combes et al. (2007), 3 = Welch & Sage (2003), 4 = Sage et al. (2007), 5 = Wiklind et al. (1995), 6 = Young (2002), and 7 = Welch et al. (2010).”
• MORPHOLOGICAL QUENCHING OF STAR FORMATION: MAKING EARLY-TYPE GALAXIES RED (2009, background): “In the Local Volume, the gas content of red ETGs (ellipticals and S0s) is often less than 1% of the baryonic mass, if detected at all (e.g., Bregman et al. 1992 for atomic gas, Combes et al. 2007 for molecular gas).”
• The SAURON project – XVII. Stellar population analysis of the absorption line strength maps of 48 early-type galaxies (2010, background): “All of the above galaxies are also detected in a systematic single dish CO survey of theSAURON sample (Combes et al. 2007) further supporting the scenario of recent star-formation.”