The ATLAS3D project - XIV. The extent and kinematics of the molecular gas in early-type galaxies

By T. Davis, K. Alatalo, M. Bureau, M. Cappellari, Nicholas Scott, L. M. Young, L. Blitz, A. Crocker, E. Bayet, M. Bois and 16 more. 2012

159 citations recorded by the source corpus.

We use interferometric (CO)-C-12(1-0) observations to compare and contrast the extent, surface brightness profiles and kinematics of the molecular gas in CO-rich ATLAS(3D) early-type galaxies (ETGs) and spiral galaxies. We find that the molecular gas extent is smaller in absolute terms in ETGs than in late-type galaxies, but that the size distributions are similar once scaled by the galaxies optical/stellar characteristic scalelengths. Amongst ETGs, we find that the extent of the gas is independent of its kinematic misalignment (with respect to the stars), but does depend on the environment, with Virgo cluster ETGs having less extended molecular gas reservoirs, further emphasizing that cluster ETGs follow different evolutionary pathways from those in the field. Approximately half of ETGs have molecular gas surface brightness profiles that follow the stellar light profile. These systems often have relaxed gas out to large radii, suggesting they are unlikely to have had recent merger/accretion events. A third of the sample galaxies show molecular gas surface brightness profiles that fall off slower than the light, and sometimes show a truncation. These galaxies often have a low mass, and either have disturbed molecular gas or are in the Virgo cluster, suggesting that recent mergers, ram pressure stripping and/or the presence of hot gas can compress/truncate the gas. The remaining galaxies have rings, or composite profiles, that we argue can be caused by the effects of bars. We investigated the kinematics of the molecular gas using position-velocity diagrams, and compared the observed kinematics with dynamical model predictions, and the observed stellar and ionized gas velocities. We confirm that the molecular gas reaches beyond the turnover of the circular velocity curve in approximate to 70 per cent of our CO-rich ATLAS(3D) ETGs, validating previous work on the CO Tully-Fisher relation. In general we find that in most galaxies the molecular gas is dynamically cold, and the observed CO rotation matches well model predictions of the circular velocity. In the galaxies with the largest molecular masses, dust obscuration and/or population gradients can cause model predictions of the circular velocity to disagree with observations of the molecular gas rotation; however, these effects are confined to the most star forming systems. Bars and non-equilibrium conditions can also make the gas deviate from circular orbits. In both these cases, one expects the model circular velocity to be higher than the observed CO velocity, in agreement with our observations. Molecular gas is a better direct tracer of the circular velocity than the ionized gas, justifying its use as a kinematic tracer for Tully-Fisher and similar analyses.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/cae40e8087ed0a00f7706de1b4fb516ba94ed647

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In Astronomy and Astrophysics

1. M. Cappellari
2. M. Sarzi
3. T. Naab
4. Roger Davies
5. Eric Emsellem
6. P. Hopkins
7. M. Bureau
8. D. Krajnovi'c

In Instrumentation

1. M. Cappellari
2. M. Sarzi
3. M. Bureau
4. Eric Emsellem
5. T. Naab
6. D. Krajnovi'c
7. Roger Davies
8. P. de Zeeuw

Citations in the corpus

• The green valley is a red herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early-and late-type galaxies (2014, background): “Studies of gas kinematics (molecular, ionized) show that most early-type galaxies, and specifically those in the green valley, have gas with an external origin, most likely due to merger activity (Sarzi et al. 2006; Shapiro et al. 2010; Davis et al. 2013; Khochfar & Burkert 2003).”
• The fast molecular outflow in the Seyfert galaxy IC 5063 as seen by ALMA (2015, background): “…in the available and new observing facilities, has opened new and important avenues for the study of formation and evolution of early-type galaxies using this component of their interstellar medium (ISM; see e.g. Young et al. 2011; Serra et al. 2012, 2014; Davis et al. 2013; Alatalo et al. 2013).”
• The ATLAS3D Project – XXX. Star formation histories and stellar population scaling relations of early-type galaxies (2015, background): “They do not show any preferred kinematic misalignment (Davis et al. 2013), and are not Virgo cluster members except for one, NGC 4694, which is a low-mass object in the outskirts of Virgo.”
• The ATLAS3D Project – XXVIII. Dynamically driven star formation suppression in early-type galaxies (2014, methodology): “To search for signs of such changes in molecular gas properties, we correlated the SFE of our molecular gas rich ETGs with the molecular gas line ratios presented for some of these objects in Krips et al. (2010); Crocker et al. (2012) and Davis et al. (2013b).”
• One Law to Rule Them All: The Radial Acceleration Relation of Galaxies (2016, methodology): “We have three ETGs in common with Davis et al. (2013).”