Prof. Dimitra Rigopoulou

Abstract:

We present ALMA Band 612CO(2-1) line and rest-frame 232 GHz continuum observations of the nearby Compton-thick Seyfert galaxy NGC 5643 with angular resolutions 0.″11-0.″26 (9-21 pc). The CO(2-1) integrated line map reveals emission from the nuclear and circumnuclear region with a two-arm nuclear spiral extending ∼10″ on each side. The circumnuclear CO(2-1) kinematics can be fitted with a rotating disk, although there are regions with large residual velocities and/or velocity dispersions. The CO(2-1) line profiles of these regions show two different velocity components. One is ascribed to the circular component and the other to the interaction of the AGN outflow, as traced by the [O iii]λ5007 Åemission, with molecular gas in the disk a few hundred parsecs from the AGN. On nuclear scales, we detected an inclined CO(2-1) disk (diameter 26 pc, FWHM) oriented almost in a north-south direction. The CO(2-1) nuclear kinematics can be fitted with a rotating disk that appears to be tilted with respect to the large-scale disk. There are strong non-circular motions in the central 0.″2-0.″3 with velocities of up to 110 km s-1. In the absence of a nuclear bar, these motions could be explained as radial outflows in the nuclear disk. We estimate a total molecular gas mass for the nuclear disk of M(H2) = 1.1 ×107Moand an H2column density toward the location of the AGN of N(H2) ∼ 5 ×1023cm-2, for a standard CO-to-H2conversion factor. We interpret this nuclear molecular gas disk as the obscuring torus of NGC 5643 as well as the collimating structure of the ionization cone.

Abstract:

The submillimeter galaxy (SMG) HERMES J105751.1+573027 (hereafter HLock01) at z =2.9574 ±0.0001 is one of the brightest gravitationally lensed sources discovered in the Herschel Multi-tiered Extragalactic Survey. Apart from the high flux densities in the far-infrared, it is also extremely bright in the rest-frame ultraviolet (UV), with a total apparent magnitude mUV≃ 19.7 mag. We report here deep spectroscopic observations with the Gran Telescopio Canarias of the optically bright lensed images of HLock01. Our results suggest that HLock01 is a merger system composed of the Herschel-selected SMG and an optically bright Lyman break-like galaxy (LBG), separated by only 3.3 kpc in projection. While the SMG appears very massive (M∗≃ 5 ×1011Mo), with a highly extinguished stellar component (AV≃ 4.3), the LBG is a young, lower-mass (M∗≃ 1 ×1010Mo), but still luminous (10 × LUV∗) satellite galaxy. Detailed analysis of the high signal-to-noise ratio (S/N) rest-frame UV spectrum of the LBG shows complex kinematics of the gas, exhibiting both blueshifted and redshifted absorption components. While the blueshifted component is associated with strong galactic outflows from the massive stars in the LBG, as is common in most star-forming galaxies, the redshifted component may be associated with gas inflow seen along a favorable sightline to the LBG. We also find evidence of an extended gas reservoir around HLock01 at an impact parameter of 110 kpc, through the detection of C ii λλ1334 absorption in the red wing of a bright Lyα emitter at z ≃ 3.327. The data presented here highlight the power of gravitational lensing in high S/N studies to probe deeply into the physics of high-z star-forming galaxies.