226 research outputs found
The 3-Dimensional Structure of HH 32 from GMOS IFU Spetroscopy
We present new high resolution spectroscopic observations of the Herbig-Haro
object HH 32 from System Verification observations made with the GMOS IFU at
Gemini North Observatory. The 3D spectral data covers a 8''.7 x 5''.85 spatial
field and 4820 - 7040 Angstrom spectral region centered on the HH~32 A knot
complex. We show the position-dependent line profiles and radial velocity
channel maps of the Halpha line, as well as line ratio velocity channel maps of
[OIII]5007/Halpha, [OI]6300/Halpha, [NII]6583/Halpha, [SII](6716+6730)/Halpha
and [SII]6716/6730. We find that the line emission and the line ratios vary
significantly on spatial scales of ~1'' and over velocities of ~50 km/s. A
``3/2-D'' bow shock model is qualitatively successful at reproducing the
general features of the radial velocity channel maps, but it does not show the
same complexity as the data and it fails to reproduce the line ratios in our
high spatial resolution maps. The observations of HH 32 A show two or three
superimposed bow shocks with separations of ~3'', which we interpret as
evidence of a line of sight superposition of two or three working surfaces
located along the redshifted body of the HH 32 outflow.Comment: Accepted for Publication in the Astronomical Journal (January 2004
A Micro Molecular Bipolar Outflow From HL Tau
We present detailed geometry and kinematics of the inner outflow toward HL
Tau observed using Near Infrared Integral Field Spectograph (NIFS) at the
Gemini-North 8-m Observatory. We analyzed H2 2.122 um emission and [Fe II]
1.644 um line emission as well as the adjacent continuum observed at a <0".2
resolution. The H2 emission shows (1) a bubble-like geometry to the northeast
of the star, as briefly reported in the previous paper, and (2) faint emission
in the southwest counterflow, which has been revealed through careful analysis.
The emission on both sides of the star show an arc 1".0 away from the star,
exhibiting a bipolar symmetry. Different brightness and morphologies in the
northeast and southwest flows are attributed to absorption and obscuration of
the latter by a flattened envelope and a circumstellar disk. The H2 emission
shows a remarkably different morphology from the collimated jet seen in [Fe II]
emission. The positions of some features coincide with scattering continuum,
indicating that these are associated with cavities in the dusty envelope. Such
properties are similar to millimeter CO outflows, although the spatial scale of
the H2 outflow in our image (~150 AU) is strikingly smaller than the mm
outflows, which often extend over 1000-10000 AU scales. The position-velocity
diagram of the H2 and [Fe II] emission do not show any evidence for kinematic
interaction between these flows. All results described above support the
scenario that the jet is surrounded by an unseen wide-angled wind, which
interacts with the ambient gas and produce the bipolar cavity and shocked H2
emission.Comment: 13 pages, 4 figures, accepted for publication in ApJ
Spatially Resolved Molecular Hydrogen Emission in the Inner 200AU Environments of Classical T Tauri Stars
We present 2.0-2.4micron integral field spectroscopy at adaptive optics
spatial resolution (~0.''1) obtained with the Near-infrared Integral Field
Spectrograph (NIFS) at Gemini North Observatory of six Classical T Tauri stars:
T Tau, DG Tau, XZ Tau, HL Tau, RW Aur and HV Tau C. In all cases, the v=1-0
S(1) (2.12 micron) emission is detected at spatially extended distances from
the central stars. The bulk of the H_2 emission is typically not spatially
coincident with the location of continuum flux. Multiple transitions detected
in the K-band spectra show that H_2 level populations are typical of gas in
thermal equilibrium with excitation temperatures in the 1800K-2300 K range.
Three of the stars have H_2 velocity profiles that are centered at the stellar
radial velocity, and three show velocity shifts with respect to the system.
Each of the stars studied here show observed excitation temperatures, spatial
extents, and kinematics of the H_2 that are most consistent with shock excited
emission from the inner regions of the known Herbig-Haro energy flows or from
wide-angle winds encompassing the outflows rather than predominantly from UV or
X-ray stimulated emission from the central stars. The data presented in this
study highlights the sensitivity of adaptive optics-fed integral field
spectroscopy for spatially resolving emission line structures in the
environments of bright young stars.Comment: 50 pages, 13 Figures. Accepted for publication in the Astrophysical
Journal. Full Resolution paper available at:
http://www.astro.sunysb.edu/tracy/pubs/Beck07.pd
Stable and Unstable Regimes of Mass Accretion onto RW Aur A
We present monitoring observations of the active T Tauri star RW Aur, from
2010 October to 2015 January, using optical high-resolution (R>10000)
spectroscopy with CFHT-ESPaDOnS. Optical photometry in the literature shows
bright, stable fluxes over most of this period, with lower fluxes (by 2-3 mag.)
in 2010 and 2014. In the bright period our spectra show clear photospheric
absorption, complicated variation in the Ca II 8542 A emission}profile shapes,
and a large variation in redshifted absorption in the O I 7772 and 8446 A and
He I 5876 A lines, suggesting unstable mass accretion during this period. In
contrast, these line profiles are relatively uniform during the faint periods,
suggesting stable mass accretion. During the faint periods the photospheric
absorption lines are absent or marginal, and the averaged Li I profile shows
redshifted absorption due to an inflow. We discuss (1) occultation by
circumstellar material or a companion and (2) changes in the activity of mass
accretion to explain the above results, together with near-infrared and X-ray
observations from 2011-2015. Neither scenario can simply explain all the
observed trends, and more theoretical work is needed to further investigate
their feasibilities.Comment: 23 pages, 11 figures, 4 tables, accepted by Astrophysical Journal;
some typos corrected on 4/18/201
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.Comment: 10 pages, 5 figures. Accepted for publication in the Astrophysical
Journa
- âŠ