991 research outputs found
A Submillimeter Study of the Star-Forming Region NGC7129
New molecular (13CO J=3-2) and dust continuum (450 and 850 micron) SCUBA maps
of the NGC7129 star forming region are presented, complemented by C18O J=3-2
spectra at several positions within the mapped region. The maps include the
Herbig Ae/Be star LkHalpha 234, the far-infrared source NGC 7129 FIRS2 and
several other pre-stellar sources embedded within the molecular ridge.
The SCUBA maps help us understand the nature of the pre-main sequence stars
in this actively star forming region. A deeply embedded submillimeter source,
SMM2, not clearly seen in any earlier data set, is shown to be a pre-stellar
core or possibly a protostar. The highest continuum peak emission is identified
with the deeply embedded source IRS6, a few arcseconds away from LkHalpha 234,
and also responsible for both the optical jet and the molecular outflow. The
gas and dust masses are found to be consistent, suggesting little or no CO
depletion onto grains. The dust emissivity index is lower towards the dense
compact sources, beta ~1 - 1.6, and higher, beta ~ 2.0, in the surrounding
cloud, implying small size grains in the PDR ridge, whose mantles have been
evaporated by the intense UV radiation.Comment: Accepted by Ap
Cold Dust in Kepler's Supernova Remnant
The timescales to replenish dust from the cool, dense winds of Asymptotic
Giant Branch stars are believed to be greater than the timescales for dust
destruction. In high redshift galaxies, this problem is further compounded as
the stars take longer than the age of the Universe to evolve into the dust
production stages. To explain these discrepancies, dust formation in supernovae
(SNe) is required to be an important process but until very recently dust in
supernova remnants has only been detected in very small quantities. We present
the first submillimeter observations of cold dust in Kepler's supernova remnant
(SNR) using SCUBA. A two component dust temperature model is required to fit
the Spectral Energy Distribution (SED) with K and K. The total mass of dust implied for Kepler is -
1000 times greater than previous estimates. Thus SNe, or their progenitors may
be important dust formation sites.Comment: 12 pages, 2 figures, accepted to ApJL, corrected proof
Star Formation in the Northern Cloud Complex of NGC 2264
We have made continuum and spectral line observations of several outflow
sources in the Mon OB1 dark cloud (NGC 2264) using the Heinrich Hertz Telescope
(HHT) and ARO 12m millimeter-wave telescope. This study explores the kinematics
and outflow energetics of the young stellar systems observed and assesses the
impact star formation is having on the surrounding cloud environment. Our data
set incorporates 12CO(3-2), 13CO(3-2), and 12CO(1-0) observations of outflows
associated with the sources IRAS 06382+1017 and IRAS 06381+1039, known as IRAS
25 and 27, respectively, in the northern cloud complex. Complementary 870
micron continuum maps were made with the HHT 19 channel bolometer array. Our
results indicate that there is a weak (approximately less than 0.5%) coupling
between outflow kinetic energy and turbulent energy of the cloud. An analysis
of the energy balance in the IRAS 25 and 27 cores suggests they are maintaining
their dynamical integrity except where outflowing material directly interacts
with the core, such as along the outflow axes.Comment: 28 pages including 6 figures, to be published in ApJ 01 July 2006,
v645, 1 issu
Submillimeter Observations of the Ultraluminous BAL Quasar APM 08279+5255
With an inferred bolometric luminosity of 5\times10^{15}{\rm \lsun}, the
recently identified z=3.87, broad absorption line quasar APM 08279+5255 is
apparently the most luminous object currently known. As half of its prodigious
emission occurs in the infrared, APM 08279+5255 also represents the most
extreme example of an Ultraluminous Infrared Galaxy. Here, we present new
submillimeter observations of this phenomenal object; while indicating that a
vast quantity of dust is present, these data prove to be incompatible with
current models of emission mechanisms and reprocessing in ultraluminous
systems. The influence of gravitational lensing upon these models is considered
and we find that while the emission from the central continuum emitting region
may be significantly enhanced, lensing induced magnification cannot easily
reconcile the models with observations. We conclude that further modeling,
including the effects of any differential magnification is required to explain
the observed emission from APM 08279+5255.Comment: 12 Pages with Two figures. Accepted for publication in the
Astrophysical Journal Letter
The Molecular Gas Environment around Two Herbig Ae/Be Stars: Resolving the Outflows of LkHa 198 and LkHa 225S
Observations of outflows associated with pre-main-sequence stars reveal
details about morphology, binarity and evolutionary states of young stellar
objects. We present molecular line data from the Berkeley-Illinois-Maryland
Association array and Five Colleges Radio Astronomical Observatory toward the
regions containing the Herbig Ae/Be stars LkHa 198 and LkHa 225S. Single dish
observations of 12CO 1-0, 13CO 1-0, N2H+ 1-0 and CS 2-1 were made over a field
of 4.3' x 4.3' for each species. 12CO data from FCRAO were combined with high
resolution BIMA array data to achieve a naturally-weighted synthesized beam of
6.75'' x 5.5'' toward LkHa 198 and 5.7'' x 3.95'' toward LkHa 225S,
representing resolution improvements of factors of approximately 10 and 5 over
existing data. By using uniform weighting, we achieved another factor of two
improvement. The outflow around LkHa 198 resolves into at least four outflows,
none of which are centered on LkHa 198-IR, but even at our resolution, we
cannot exclude the possibility of an outflow associated with this source. In
the LkHa 225S region, we find evidence for two outflows associated with LkHa
225S itself and a third outflow is likely driven by this source. Identification
of the driving sources is still resolution-limited and is also complicated by
the presence of three clouds along the line of sight toward the Cygnus
molecular cloud. 13CO is present in the environments of both stars along with
cold, dense gas as traced by CS and (in LkHa 225S) N2H+. No 2.6 mm continuum is
detected in either region in relatively shallow maps compared to existing
continuum observations.Comment: 14 pages, 10 figures (5 color), accepted for publication in Ap
Submillimeter spectroscopy of southern hot cores: NGC6334(I) and G327.3-0.6
High-mass star-forming regions are known to have a rich molecular spectrum
from many species. Some of the very highly excited lines are emitted from very
hot and dense gas close to the central object(s). The physics and chemistry of
the inner cores of two high mass star forming regions, NGC6334(I) and
G327.3-0.6, shall be characterized. Submillimeter line surveys with the APEX
telescope provide spectra which sample many molecular lines at high excitation
stages. Partial spectral surveys were obtained, the lines were identified,
physical parameters were determined through fitting of the spectra. Both
sources show similar spectra that are comparable to that of the only other high
mass star forming region ever surveyed in this frequency range}, Orion-KL, but
with an even higher line density. Evidence for very compact, very hot sources
is found.Comment: APEX A&A special issue, accepte
Probing the Early Stages of Low-Mass Star Formation in LDN 1689N: Dust and Water in IRAS 16293-2422A, B, and E
We present deep images of dust continuum emission at 450, 800, and 850 micron
of the dark cloud LDN 1689N which harbors the low-mass young stellar objects
(YSOs) IRAS 16293-2422A and B (I16293A and I16293B) and the cold prestellar
object I16293E. Toward the positions of I16293A and E we also obtained spectra
of CO-isotopomers and deep submillimeter observations of chemically related
molecules with high critical densities. To I16293A we report the detection of
the HDO 1_01 - 0_00 and H2O 1_10 - 1_01 ground-state transitions as broad
self-reversed emission profiles with narrow absorption, and a tentative
detection of H2D+ 1_10 - 1_11. To I16293E we detect weak emission of
subthermally excited HDO 1_01 - 0_00. Based on this set of submillimeter
continuum and line data we model the envelopes around I16293A and E. The
density and velocity structure of I16293A is fit by an inside-out collapse
model, yielding a sound speed of a=0.7 km/s, an age of t=(0.6--2.5)e4 yr, and a
mass of 6.1 Msun. The density in the envelope of I16293E is fit by a radial
power law with index -1.0+/-0.2, a mass of 4.4 Msun, and a constant temperature
of 16K. These respective models are used to study the chemistry of the
envelopes of these pre- and protostellar objects.
The [HDO]/[H2O] abundance ratio in the warm inner envelope of I16293A of a
few times 1e-4 is comparable to that measured in comets. This supports the idea
that the [HDO]/[H2O] ratio is determined in the cold prestellar core phase and
conserved throughout the formation process of low-mass stars and planets.Comment: 61 pages, 17 figures. Accepted for publication in ApJ. To get Fig.
13: send email to [email protected]
Star Formation in Massive Protoclusters in the Monoceros OB1 Dark Cloud
We present far-infrared, submillimetre, and millimetre observations of bright
IRAS sources and outflows that are associated with massive CS clumps in the
Monoceros OB1 Dark Cloud. Individual star-forming cores are identified within
each clump. We show that combining submillimetre maps, obtained with SCUBA on
the JCMT, with HIRES-processed and modelled IRAS data is a powerful technique
that can be used to place better limits on individual source contributions to
the far-infrared flux in clustered regions. Three previously categorized "Class
I objects" are shown to consist of multiple sources in different evolutionary
stages. In each case, the IRAS point source dominates the flux at 12 and 25
microns. In two cases, the IRAS point source is not evident at submillimetre
wavelengths. The submillimetre sources contribute significantly to the 60 and
100 micron fluxes, dominating the flux in the 100 micron waveband. Using fluxes
derived from our technique, we present the spectral energy distribution and
physical parameters for an intermediate-mass Class 0 object in one of the
regions. Our new CO J=2-1 outflow maps of the three regions studied indicate
complex morphology suggestive of multiple driving sources. We discuss the
possible implications of our results for published correlations between outflow
momentum deposition rates and "source" luminosities, and for using these
derived properties to estimate the ratio of mass ejection rates to mass
accretion rates onto protostars.Comment: 12 pages, 11 gzipped gif figures, LaTex file and MNRAS style files,
accepted by MNRAS, v2: reference typos and author affiliation have been
correcte
Digging into NGC 6334I(N): Multiwavelength Imaging of a Massive Protostellar Cluster
We present a high-resolution, multi-wavelength study of the massive
protostellar cluster NGC 6334I(N) that combines new spectral line data from the
Submillimeter Array (SMA) and VLA with a reanalysis of archival VLA continuum
data, 2MASS and Spitzer images. As shown previously, the brightest 1.3 mm
source SMA1 contains substructure at subarcsecond resolution, and we report the
first detection of SMA1b at 3.6 cm along with a new spatial component at 7 mm
(SMA1d). We find SMA1 (aggregate of sources a, b, c, and d) and SMA4 to be
comprised of free-free and dust components, while SMA6 shows only dust
emission. Our 1.5" resolution 1.3 mm molecular line images reveal substantial
hot-core line emission toward SMA1 and to a lesser degree SMA2. We find CH3OH
rotation temperatures of 165\pm 9 K and 145\pm 12 K for SMA1 and SMA2,
respectively. We estimate a diameter of 1400 AU for the SMA1 hot core emission,
encompassing both SMA1b and SMA1d, and speculate that these sources comprise a
>800 AU separation binary that may explain the previously-suggested precession
of the outflow emanating from the SMA1 region. The LSR velocities of SMA1,
SMA2, and SMA4 all differ by 1-2 km/s. Outflow activity from SMA1, SMA2, SMA4,
and SMA6 is observed in several molecules including SiO(5--4) and IRAC 4.5
micron emission; 24 micron emission from SMA4 is also detected. Eleven water
maser groups are detected, eight of which coincide with SMA1, SMA2, SMA4, and
SMA6. We also detect a total of 83 Class I CH3OH 44GHz maser spots which likely
result from the combined activity of many outflows. Our observations paint the
portrait of multiple young hot cores in a protocluster prior to the stage where
its members become visible in the near-infrared.Comment: Accepted to ApJ, 24 pages, a full high resolution version is
available at http://www.cv.nrao.edu/~cbrogan/ms.long.pd
Class I methanol masers in low-mass star formation regions
Four Class I maser sources were detected at 44, 84, and 95 GHz toward
chemically rich outflows in the regions of low-mass star formation NGC 1333I4A,
NGC 1333I2A, HH25, and L1157. One more maser was found at 36 GHz toward a
similar outflow, NGC 2023. Flux densities of the newly detected masers are no
more than 18 Jy, being much lower than those of strong masers in regions of
high-mass star formation. The brightness temperatures of the strongest peaks in
NGC 1333I4A, HH25, and L1157 at 44 GHz are higher than 2000 K, whereas that of
the peak in NGC 1333I2A is only 176 K. However, rotational diagram analysis
showed that the latter source is also a maser. The main properties of the newly
detected masers are similar to those of Class I methanol masers in regions of
massive star formation. The former masers are likely to be an extension of the
latter maser population toward low luminosities of both the masers and the
corresponding YSOs.Comment: 5 pages, 1 figure, Proc. IAU Symp. 287 "Cosmic Masers: from OH to
H0". LSR velocities of the HH25 masers, which are presented in Table 1, are
correcte
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