Tracy Beck — Page 2

arXiv2008

Mapping of the molecular gas inflow towards the Seyfert nucleus of NGC4051 using Gemini NIFS

We present two-dimensional (2D) stellar and gaseous kinematics of the inner ~130x180 pc^2 of the Narrow Line Seyfert 1 galaxy NGC4051 at a sampling of 4.5 pc, from near-infrared K-band spectroscopic observations obtained with the Gemini's Near-infrared Integral Field Spectrograph (NIFS). The turnover of the stellar rotation curve at only ~55 pc from the nucleus, revealing a highly concentrated gravitational potential. The stellar velocity dispersion of the bulge is ~60 km/s -- implying on a nuclear black hole mass of ~10^6 M_sun -- within which patches of lower velocity dispersion suggest the presence of regions of more recent star formation. The Brgamma emission-line shows no rotation as well as no blueshifts or redshifts in excess of 30 km/s, and is thus not restricted to the galaxy plane. The [CaVIII] coronal region is compact but resolved, extending over the inner 75 pc. It shows the highest blueshifts -- of up to -250 km/s, and the highest velocity dispersions, interpreted as due to outflows from the active nucleus, supporting an origin close to the nucleus. Subtraction of the stellar velocity field from the gaseous velocity field has allowed us to isolate non-circular motions observed in the H_2 emitting gas. The most conspicuous kinematic structures are two nuclear spiral arms. We interpret these structures as inflows towards the nucleus, a result similar to those of previous studies in which we have found streaming motions along nuclear spirals in ionized gas using optical IFU observations. We have calculated the mass inflow rate along the nuclear spiral arms, obtaining $\dot{M}_{H_2} ~ 4x10^{-5} M_Sun/yr, value ~100 times smaller than the accretion rate necessary to power the active nucleus.

astro-ph↗

arXiv2007

Gemini Observations of Disks and Jets in Young Stellar Objects and in Active Galaxies

We present first results from the Near-infrared Integral Field Spectrograph (NIFS) located at Gemini North. For the active galaxies Cygnus A and Perseus A we observe rotationally-supported accretion disks and adduce the existence of massive central black holes and estimate their masses. In Cygnus A we also see remarkable high-excitation ionization cones dominated by photoionization from the central engine. In the T-Tauri stars HV Tau C and DG Tau we see highly-collimated bipolar outflows in the [Fe II] 1.644 micron line, surrounded by a slower molecular bipolar outflow seen in the H_2 lines, in accordance with the model advocated by Pyo et al. (2002).

astro-ph↗

arXiv2001

Evidence for Extinction and Accretion Variability in T Tau S

We present angularly resolved spectra of T Tau North and South in the 3 micron water ice feature and K-band. Most of the water ice absorption lies along the line of sight toward T Tau South, confirming that it is viewed through stronger extinction. A decrease in ice-band absorption toward T Tau S between December 1998 and January 2000, significant at the 2 sigma level, was associated with an increase in its near infrared flux. Br gamma emission is detected in T Tau North and South and H_{2} (2.12 micron) emission only toward T Tau South, consistent with previous studies of infrared companions to T Tauri stars. Our results suggest that the near IR variability of T Tau S is probably caused by both variations in accretion rate and variable extinction along the line of sight.

astro-ph↗