606 research outputs found
Absorption Line Survey of H3+ toward the Galactic Center Sources III. Extent of the Warm and Diffuse Clouds
We present follow-up observations to those of Geballe & Oka (2010), who found
high column densities of H3+ ~100 pc off of the Galactic center (GC) on the
lines of sight to 2MASS J17432173-2951430 (J1743) and 2MASS J17470898-2829561
(J1747). The wavelength coverages on these sightlines have been extended in
order to observe two key transitions of H3+, R(3,3)l and R(2,2)l, that
constrain the temperatures and densities of the environments. The profiles of
the H3+ R(3,3)l line, which is due only to gas in the GC, closely matches the
differences between the H3+ R(1,1)l and CO line profiles, just as it does for
previously studied sightlines in the GC. Absorption in the R(2,2)l line of H3+
is present in J1747 at velocities between -60 and +100 km/s. This is the second
clear detection of this line in the interstellar medium after GCIRS 3 in the
Central Cluster. The temperature of the absorbing gas in this velocity range is
350 K, significantly warmer than in the diffuse clouds in other parts of the
Central Molecular Zone. This indicates that the absorbing gas is local to Sgr B
molecular cloud complex. The warm and diffuse gas revealed by Oka et al. (2005)
apparently extends to ~100 pc, but there is a hint that its temperature is
somewhat lower in the line of sight to J1743 than elsewhere in the GC. The
observation of H3+ toward J1747 is compared with the recent Herschel
observation of H2O+ toward Sgr B2 and their chemical relationship and
remarkably similar velocity profiles are discussed.Comment: 6 pages, 3 figures, 2 tables, Accepted for publication in
Publications of the Astronomical Society of Japa
Fundamental Vibrational Transitions of HCl Detected in CRL 2136
We would like to understand the chemistry of dense clouds and their hot cores
more quantitatively by obtaining more complete knowledge of the chemical
species present in them. We have obtained high-resolution infrared absorption
spectroscopy at 3-4 um toward the bright infrared source CRL 2136. The
fundamental vibration-rotation band of HCl has been detected within a dense
cloud for the first time. The HCl is probably located in the warm compact
circumstellar envelope or disk of CRL 2136. The fractional abundance of HCl is
(4.9-8.7)e-8, indicating that approximately 20 % of the elemental chlorine is
in gaseous HCl. The kinetic temperature of the absorbing gas is 250 K, half the
value determined from infrared spectroscopy of 13CO and water. The percentage
of chlorine in HCl is approximately that expected for gas at this temperature.
The reason for the difference in temperatures between the various molecular
species is unknown.Comment: 6 pages, 3 figures, A&A in pres
Infrared Spectroscopy of CO Ro-vibrational Absorption Lines toward the Obscured AGN IRAS 08572+3915
We present high-resolution spectroscopy of gaseous CO absorption in the
fundamental ro-vibrational band toward the heavily obscured active galactic
nucleus (AGN) IRAS 08572+3915. We have detected absorption lines up to highly
excited rotational levels (J<=17). The velocity profiles reveal three distinct
components, the strongest and broadest (delta_v > 200 km s-1) of which is due
to blueshifted (-160 km s-1) gas at a temperature of ~ 270 K absorbing at
velocities as high as -400 km s-1. A much weaker but even warmer (~ 700 K)
component, which is highly redshifted (+100 km s-1), is also detected, in
addition to a cold (~ 20 K) component centered at the systemic velocity of the
galaxy. On the assumption of local thermodynamic equilibrium, the column
density of CO in the 270 K component is NCO ~ 4.5 x 10^18 cm-2, which in fully
molecular gas corresponds to a H2 column density of NH2 ~ 2.5 x 10^22 cm-2. The
thermal excitation of CO up to the observed high rotational levels requires a
density greater than nc(H2) > 2 x 10^7 cm-3, implying that the thickness of the
warm absorbing layer is extremely small (delta_d < 4 x 10-2 pc) even if it is
highly clumped. The large column densities and high radial velocities
associated with these warm components, as well as their temperatures, indicate
that they originate in molecular clouds near the central engine of the AGN.Comment: 13 pages, 7 figures, accepted for publication in PASJ (Vol.65 No.1
2013/02/25
The Interstellar Medium of IRAS 08572+3915 NW: H3+ and Warm High Velocity CO
We confirm the first detection of the molecular ion H3+ in an extragalactic
object, the highly obscured ultraluminous galaxy IRAS 08572+3915 NW. We also
have detected absorption lines of the fundamental band of CO in this galaxy.
The CO absorption consists of a cold component close to the systemic velocity
and warm, highly blueshifted and redshifted components. The warm blueshifted
component is remarkably strong and broad and extends at least to -350 km/s.
Some analogies can be drawn between the H3+ and cold CO in IRAS08572+3915 NW
and the same species seen toward the Galactic center. The profiles of the warm
CO components are not those expected from a dusty torus of the type thought to
obscure active galactic nuclei. They are probably formed close to the dust
continuum surface near the buried and active nucleus and are probably
associated with an unusual and energetic event there.Comment: 21 pages, 4 postscript figures, accepted by Ap
Constraints on core-collapse supernova progenitors from explosion site integral field spectroscopy
Observationally, supernovae (SNe) are divided into subclasses pertaining to
their distinct characteristics. This diversity reflects the diversity in the
progenitor stars. It is not entirely clear how different evolutionary paths
leading massive stars to become a SN are governed by fundamental parameters
such as progenitor initial mass and metallicity. This paper places constraints
on progenitor initial mass and metallicity in distinct core-collapse SN
subclasses, through a study of the parent stellar populations at the explosion
sites. Integral field spectroscopy (IFS) of 83 nearby SN explosion sites with a
median distance of 18 Mpc has been collected and analysed, enabling detection
and spectral extraction of the parent stellar population of SN progenitors.
From the parent stellar population spectrum, the initial mass and metallicity
of the coeval progenitor are derived by means of comparison to simple stellar
population models and strong-line methods. Additionally, near-infrared IFS was
employed to characterise the star formation history at the explosion sites. No
significant metallicity differences are observed among distinct SN types. The
typical progenitor mass is found to be highest for SN Ic, followed by type Ib,
then types IIb and II. SN IIn is the least associated with young stellar
populations and thus massive progenitors. However, statistically significant
differences in progenitor initial mass are observed only when comparing SNe IIn
with other subclasses. Stripped-envelope SN progenitors with initial mass
estimate lower than 25~ are found; these are thought to be the result
of binary progenitors. Confirming previous studies, these results support the
notion that core-collapse SN progenitors cannot arise from single-star channel
only, and both single and binary channels are at play in the production of
core-collapse SNe. [ABRIDGED]Comment: 18 pages, 10 figures, accepted to A&
Plane-wave based electronic structure calculations for correlated materials using dynamical mean-field theory and projected local orbitals
The description of realistic strongly correlated systems has recently
advanced through the combination of density functional theory in the local
density approximation (LDA) and dynamical mean field theory (DMFT). This
LDA+DMFT method is able to treat both strongly correlated insulators and
metals. Several interfaces between LDA and DMFT have been used, such as (N-th
order) Linear Muffin Tin Orbitals or Maximally localized Wannier Functions.
Such schemes are however either complex in use or additional simplifications
are often performed (i.e., the atomic sphere approximation). We present an
alternative implementation of LDA+DMFT, which keeps the precision of the
Wannier implementation, but which is lighter. It relies on the projection of
localized orbitals onto a restricted set of Kohn-Sham states to define the
correlated subspace. The method is implemented within the Projector Augmented
Wave (PAW) and within the Mixed Basis Pseudopotential (MBPP) frameworks. This
opens the way to electronic structure calculations within LDA+DMFT for more
complex structures with the precision of an all-electron method. We present an
application to two correlated systems, namely SrVO3 and beta-NiS (a
charge-transfer material), including ligand states in the basis-set. The
results are compared to calculations done with Maximally Localized Wannier
functions, and the physical features appearing in the orbitally resolved
spectral functions are discussed.Comment: 15 pages, 17 figure
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