Extremely Large Telescope

Abstract:

We report the detection of far-IR CO rotational emission from the prototypical Seyfert 2 galaxy NGC 1068. Using Herschel-PACS, we have detected 11 transitions in the J upper = 14-30 (E upper/kB = 580-2565K) range, all of which are consistent with arising from within the central 10″ (700pc). The detected transitions are modeled as arising from two different components: a moderate-excitation (ME) component close to the galaxy systemic velocity and a high-excitation (HE) component that is blueshifted by 80kms-1. We employ a large velocity gradient model and derive n H2 105.6cm-3, T kin 170K, and M H2 106.7 M ⊙ for the ME component and n H2 106.4cm-3, T kin 570K, and M H2 105.6 M ⊙ for the HE component, although for both components the uncertainties in the density and mass are ±(0.6-0.9)dex. Both components arise from denser and possibly warmer gas than traced by low-J CO transitions, and the ME component likely makes a significant contribution to the mass budget in the nuclear region. We compare the CO line profiles with those of other molecular tracers observed at higher spatial and spectral resolution and find that the ME transitions are consistent with these lines arising in the200pc diameter ring of material traced by H 2 1-0 S(1) observations. The blueshift of the HE lines may also be consistent with the bluest regions of this H2 ring, but a better kinematic match is found with a clump of infalling gas 40pc north of the active galactic nucleus (AGN). We consider potential heating mechanisms and conclude that X-ray- or shock heating of both components is viable, while far-UV heating is unlikely. We discuss the prospects of placing the HE component near the AGN and conclude that while the moderate thermal pressure precludes an association with the 1pc radius H2O maser disk, the HE component could potentially be located only a few parsecs more distant from the AGN and might then provide the N H 1025cm-2 column obscuring the nuclear hard X-rays. Finally, we also report sensitive upper limits extending up to J upper = 50, which place constraints on a previous model prediction for the CO emission from the X-ray obscuring torus. © 2012 The American Astronomical Society. All rights reserved.

Abstract:

NGC 1266 is a nearby field galaxy observed as part of the ATLAS 3D survey (Cappellari et al. 2011). NGC 1266 has been shown to host a compact (< 200 pc) molecular disk and a mass-loaded molecular outflow driven by the AGN (Alatalo et al. 2011). Very Long Basline Array (VLBA) observations at 1.65 GHz revealed a compact (diameter < 1.2 pc), high brightness temperature continuum source most consistent with a low-level AGN origin. The VLBA continuum source is positioned at the center of the molecular disk and may be responsible for the expulsion of molecular gas in NGC 1266. Thus, the candidate AGN-driven molecular outflow in NGC 1266 supports the picture in which AGNs do play a significant role in the quenching of star formation and ultimately the evolution of the red sequence of galaxies. © International Astronomical Union 2013.

Abstract:

Since Edwin Hubble introduced his famous tuning fork diagram more than 70 years ago, spiral galaxies and early-type galaxies (ETGs) have been regarded as two distinct families. The spirals are characterized by the presence of disks of stars and gas in rapid rotation, while the early-types are gas poor and described as spheroidal systems, with less rotation and often non-axisymmetric shapes. The separation is physically relevant as it implies a distinct path of formation for the two classes of objects. I will give an overview of recent findings, from independent teams, that motivated a radical revision to Hubble's classic view of ETGs. These results imply a much closer link between spiral galaxies and ETGs than generally assumed.

Abstract:

According to a popular scenario supported by numerical models, the mass assembly and growth of massive galaxies, in particular the Early-Type Galaxies (ETGs), is, below a redshift of 1, mainly due to the accretion of multiple gas-poor satellites. In order to get observational evidence of the role played by minor dry mergers, we are obtaining extremely deep optical images of a complete volume limited sample of nearby ETGs. These observations, done with the CFHT as part of the ATLAS3D, NGVS and MATLAS projects, reach a stunning 28.5 - 29 mag.arcsec-2 surface brightness limit in the g' band. They allow us to detect the relics of past collisions such as faint stellar tidal tails as well as the very extended stellar halos which keep the memory of the last episodes of galactic accretion. Images and preliminary results from this on-going survey are presented, in particular a possible correlation between the fine structure index (which parametrizes the amount of tidal perturbation) of the ETGs, their stellar mass, effective radius and gas content. © 2013 International Astronomical Union.

Abstract:

Recently, massive early-type galaxies have shed their red-and-dead moniker, thanks to the discovery that many host residual star formation. As part of the ATLAS-3D project, we have conducted a complete, volume-limited survey of the molecular gas in 260 local early-type galaxies with the IRAM-30m telescope and the CARMA interferometer, in an attempt to understand the fuel powering this star formation. We find that around 22% of early-type galaxies in the local volume host molecular gas reservoirs. This detection rate is independent of galaxy luminosity and environment. Here we focus on how kinematic misalignment measurements and gas-to-dust ratios can be used to put constraints on the origin of the cold ISM in these systems. The origin of the cold ISM seems to depend strongly on environment, with misaligned, dust poor gas (indicative of externally acquired material) being common in the field but completely absent in rich groups and in the Virgo cluster. Very massive galaxies also appear to be devoid of accreted gas. This suggests that in the field mergers and/or cold gas accretion dominate the gas supply, while in clusters internal secular processes become more important. This implies that environment has a strong impact on the cold gas properties of ETGs. © 2013 International Astronomical Union.