Professor Roger Davies

Abstract:

HARMONI is a visible and near-IR integral field spectrograph, providing the E-ELT's spectroscopic capability at first light. It obtains simultaneous spectra of 32000 spaxels, at a range of resolving powers from R∼4000 to R∼20000, covering the wavelength range from 0.47 to 2.45 ìm. The 256 ? 128 spaxel field of view has four different plate scales, with the coarsest scale (40 mas) providing a 5? ? 10? FoV, while the finest scale is a factor of 10 finer (4mas). We describe the opto-mechanical design of HARMONI, prior to the start of preliminary design, including the main subsystems - namely the image de-rotator, the scale-changing optics, the splitting and slicing optics, and the spectrographs. We also present the secondary guiding system, the pupil imaging optics, the field and pupil stops, the natural guide star wavefront sensor, and the calibration unit. © 2012 SPIE.

Abstract:

We use the Spectrographic Areal Unit for Research on Optical Nebulae and Gemini Multi-Object Spectrograph integral-field spectrographs to observe the active galactic nucleus (AGN) powered outflow in NGC1266. This unusual galaxy is relatively nearby (D = 30Mpc), allowing us to investigate the process of AGN feedback in action. We present maps of the kinematics and line strengths of the ionized gas emission lines Hα, Hβ, [Oiii], [Oi], [Nii] and [Sii], and report on the detection of sodium D absorption. We use these tracers to explore the structure of the source, derive the ionized and atomic gas kinematics, and investigate the gas excitation and physical conditions. NGC1266 contains two ionized gas components along most lines of sight, tracing the ongoing outflow and a component closer to the galaxy systemic, the origin of which is unclear. This gas appears to be disturbed by a nascent AGN jet. We confirm that the outflow in NGC1266 is truly multiphase, containing radio plasma, atomic, molecular and ionized gas and X-ray emitting plasma. The outflow has velocities of up to ±900 km s-1 away from the systemic velocity and is very likely to remove significant amount of cold gas from the galaxy. The low-ionization nuclear emission region-like line emission in NGC1266 is extended, and it likely arises from fast shocks caused by the interaction of the radio jet with the interstellar medium. These shocks have velocities of up to 800 km s-1, which match well with the observed velocity of the outflow. Sodium D equivalent width profiles are used to set constraints on the size and orientation of the outflow. The ionized gas morphology correlates with the nascent radio jets observed in 1.4 and 5 GHz continuum emission, supporting the suggestion that an AGN jet is providing the energy required to drive the outflow. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Abstract:

As a demonstration of the capabilities of the new Oxford SWIFT integral field spectrograph, we present first observations for a set of 14 early-type galaxies in the core of the Coma cluster. Our data consist of I- and z-band spatially resolved spectroscopy obtained with the Oxford SWIFT spectrograph, combined with r-band photometry from the Sloan Digital Sky Survey archive for 14 early-type galaxies. We derive spatially resolved kinematics for all objects from observations of the calcium triplet absorption features at ∼8500Å. Using this kinematic information we classify galaxies as either fast rotators or slow rotators. We compare the fraction of fast and slow rotators in our sample, representing the densest environment in the nearby Universe, to results from the ATLAS3D survey, finding that the slow rotator fraction is ∼50per cent larger in the core of the Coma cluster than in the volume-limited ATLAS3D sample, a 1.2σ increase given our selection criteria. Comparing our sample to the Virgo cluster core only (which is 24 times less dense than the Coma core) we find no evidence of an increase in the slow rotator fraction. Combining measurements of the effective velocity dispersion σe with the photometric data we determine the Fundamental Plane for our sample of galaxies. We find that the use of the average velocity dispersion within 1 effective radius, σe, reduces the residuals by 13per cent with respect to comparable studies using central velocity dispersions, consistent with other recent integral field Fundamental Plane determinations. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

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:

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.