16 research outputs found
New CO and Millimeter Continuum Observations of the z=2.394 Radio Galaxy 53W002
The z=2.39 radio galaxy 53W002 lies in a cluster of Ly-alpha emission line
objects and may itself be undergoing a major burst of star formation. CO(3--2)
emission, at 102 GHz, was detected from 53W002 by Scoville et al. (1997a), who
also reported a possible 30 kpc extension and velocity gradient suggesting a
rotating gaseous disk. In this paper we present new interferometric CO(3--2)
observations which confirm the previous line detection with improved
signal-to-noise ratio, but show no evidence for source extension or velocity
gradient. The compact nature of the CO source and the molecular mass found in
this object are similar to luminous infrared galaxies and other AGNs previously
studied
Dust continuum and Polarization from Envelope to Cores in Star Formation: A Case Study in the W51 North region
We present the first high-angular resolution (up to 0.7", ~5000 AU)
polarization and thermal dust continuum images toward the massive star-forming
region W51 North. The observations were carried out with the Submillimeter
Array (SMA) in both the subcompact (SMA-SubC) and extended (SMA-Ext)
configurations at a wavelength of 870 micron. W51 North is resolved into four
cores (SMA1 to SMA4) in the 870 micron continuum image. The associated dust
polarization exhibits more complex structures than seen at lower angular
resolution. We analyze the inferred morphologies of the plane-of-sky magnetic
field (B_bot) in the SMA1 to SMA4 cores and in the envelope using the SMA-Ext
and SMA-SubC data. These results are compared with the B_bot archive images
obtained from the CSO and JCMT. A correlation between dust intensity gradient
position angles (phi_{nabla I}) and magnetic field position angles (phi_B) is
found in the CSO, JCMT and both SMA data sets. This correlation is further
analyzed quantitatively. A systematically tighter correlation between
phi_{nabla I} and phi_B is found in the cores, whereas the correlation
decreases in outside-core regions. Magnetic field-to-gravity force ratio
(Sigma_B) maps are derived using the newly developed polarization - intensity
gradient method by Koch, Tang & Ho 2012. We find that the force ratios tend to
be small (Sigma_B <= 0.5) in the cores in all 4 data sets. In regions outside
of the cores, the ratios increase or the field is even dominating gravity
(Sigma_B > 1). This possibly provides a physical explanation of the tightening
correlation between phi_{nabla I} and phi_B in the cores: the more the B field
lines are dragged and aligned by gravity, the tighter the correlation is.
Finally, we propose a schematic scenario for the magnetic field in W51 North to
interpret the four polarization observations at different physical scales.Comment: Accepted for publication in ApJ. 10 pages. 7 figure
The circumstellar disk of AB Aurigae: evidence for envelope accretion at late stages of star formation?
The circumstellar disk of AB Aurigae has garnered strong attention owing to
the apparent existence of spirals at a relatively young stage and also the
asymmetric disk traced in thermal dust emission. However, the physical
conditions of the spirals are still not well understood. The origin of the
asymmetric thermal emission is unclear.
We observed the disk at 230 GHz (1.3 mm) in both the continuum and the
spectral line ^12CO J=2-1 with IRAM 30-m, the Plateau de Bure interferometer,
and the Submillimeter Array to sample all spatial scales from 0.37" to about
50". To combine the data obtained from these telescopes, several methods and
calibration issues were checked and discussed.
The 1.3 mm continuum (dust) emission is resolved into inner disk and outer
ring. Molecular gas at high velocities traced by the CO line is detected next
to the stellar location. The inclination angle of the disk is found to decrease
toward the center. On a larger scale, based on the intensity weighted
dispersion and the integrated intensity map of ^12CO J=2-1, four spirals are
identified, where two of them are also detected in the near infrared. The total
gas mass of the 4 spirals (M_spiral) is 10^-7 < M_spiral < 10^-5 M_sun, which
is 3 orders of magnitude smaller than the mass of the gas ring. Surprisingly,
the CO gas inside the spiral is apparently counter-rotating with respect to the
CO disk, and it only exhibits small radial motion.
The wide gap, the warped disk, and the asymmetric dust ring suggest that
there is an undetected companion with a mass of 0.03 M_sun at a radius of 45
AU. Although an hypothetical fly-by cannot be ruled out, the most likely
explanation of the AB Aurigae system may be inhomogeneous accretion well above
or below the main disk plane from the remnant envelope, which can explain both
the rotation and large-scale motions detected with the 30-m image.Comment: 17 pages, 13 figures, accepted for publication in A&A journal. Typos
are correcte
Chemistry in Disks. IX. Observations and modeling of HCO+ and DCO+ in DM Tau
We present resolved Plateau de Bure Array observations of DM Tau in lines of
HCO+ (3-2), (1-0) and DCO+ (3-2). A power-law fitting approach allowed a
derivation of column densities of these two molecules. A chemical inner hole of
~50 AU was found in both HCO+ and DCO+ with DCO+ emission extending to only 450
AU. An isotopic ratio of R_D = N(DCO+) / N(HCO+) was found to range from 0.1 at
50 AU and 0.2 at 450 AU. Chemical modeling allowed an exploration of the
sensitivity of these molecular abundances to physical parameters out with
temperature, finding that X-rays were the domination ionization source in the
HCO+ molecular region and that R_D also is sensitive to the CO depletion. The
ionization fraction, assuming a steady state system, was found to be x(e-) ~
10. Modeling suggests that HCO+ is the dominant charged molecule in the
disk but its contribution to ionization fraction is dwarfed by atmoic ions such
as C+, S+ and H+.Comment: 13 pages with 8 figures, to be published in A&A, accepted 29/12/1
The second detection of CO at redshift larger than 4
We report the detection with the IRAM interferometer at 3mm of J=5-4 CO line
in the radio quiet quasar BRI1335-0415 at redshift of z=4.41. After BR1202-0725
at z=4.69 (Ohta etal 1996, Omont etal 1996a), this is the second detection of
CO at z>3. The integrated line intensity is 2.8+-0.3 Jy km s^{-1} with a
linewidth of 420+-60 km s^{-1}. The dust continuum emission has also been
mapped at 1.35mm. The 1.35mm flux is found to be 5.6+-1.1mJy. The ratio of the
CO to 1.35mm continuum flux is slightly larger than for BR1202-0725. Contrary
to the case of BR1202-0725, there is only marginal evidence of extension of the
1.35mm continuum and 3mm CO emission. In the absence of gravitational lensing,
for which there is no a priori evidence, and within the uncertainties of the CO
to M(H_2) conversion factors, the mass of molecular gas M(H_2) could be 10^{11}
solar masses.Comment: 5 pages, 3 figures, LaTex (l-aa.sty, psfig.sty), also available at
http://www.ast.cam.ac.uk/~rg
Circumbinary Ring, Circumstellar disks and accretion in the binary system UY Aurigae
Recent exo-planetary surveys reveal that planets can orbit and survive around
binary stars. This suggests that some fraction of young binary systems which
possess massive circumbinary disks (CB) may be in the midst of planet
formation. However, there are very few CB disks detected. We revisit one of the
known CB disks, the UY Aurigae system, and probe 13CO 2-1, C18O 2-1, SO
5(6)-4(5) and 12CO 3-2 line emission and the thermal dust continuum. Our new
results confirm the existence of the CB disk. In addition, the circumstellar
(CS) disks are clearly resolved in dust continuum at 1.4 mm. The spectral
indices between the wavelengths of 0.85 mm and 6 cm are found to be
surprisingly low, being 1.6 for both CS disks. The deprojected separation of
the binary is 1.26" based on our 1.4 mm continuum data. This is 0.07" (10 AU)
larger than in earlier studies. Combining the fact of the variation of UY Aur B
in band, we propose that the CS disk of an undetected companion UY Aur Bb
obscures UY Aur Ba. A very complex kinematical pattern inside the CB disk is
observed due to a mixing of Keplerian rotation of the CB disk, the infall and
outflow gas. The streaming gas accreting from the CB ring toward the CS disks
and possible outflows are also identified and resolved. The SO emission is
found to be at the bases of the streaming shocks. Our results suggest that the
UY Aur system is undergoing an active accretion phase from the CB disk to the
CS disks. The UY Aur B might also be a binary system, making the UY Aur a
triple system.Comment: 14 pages, 11 figures; accepted for publication in Ap
Spatially Resolved Millimeter Interferometry of SMMJ02399-0136: a Very Massive Galaxy at z=2.8
We report high-resolution millimeter mapping with the IRAM Plateau de Bure
interferometer of rest-frame 335 micron continuum and CO(3-2) line emission
from the z=2.8 submillimeter galaxy SMMJ02399-0136. The continuum emission
comes from a ~3" diameter structure whose elongation is approximately east-west
and whose centroid is coincident within the astrometric errors with the
brightest X-ray and rest-UV peak (L1). The line data show that this structure
is most likely a rapidly rotating disk. Its rotation velocity of >420 km/s
implies a total dynamical mass of >3x10^11 solar masses within an intrinsic
radius of 8 kpc, most of which is plausibly in the form of stars and gas.
SMMJ02399-0136 is thus a very massive system, whose formation at z~3 is not
easy to understand in current CDM hierarchical merger cosmogonies.Comment: 19 pages, 6 figures (5 PS + 1 GIF), accepted by ApJ; added color
versions of Figures 1, 5, &
Mapping CO Gas in the GG Tauri A Triple System with 50 AU Spatial Resolution
We aim to unveil the observational imprint of physical mechanisms that govern
planetary formation in the young, multiple system GG Tau A. We present ALMA
observations of CO and CO 3-2 and 0.9 mm continuum emission with
0.35" resolution. The CO 3-2 emission, found within the cavity of the
circumternary dust ring (at radius AU) where no CO emission is
detected, confirms the presence of CO gas near the circumstellar disk of GG Tau
Aa. The outer disk and the recently detected hot spot lying at the outer edge
of the dust ring are mapped both in CO and CO. The gas emission
in the outer disk can be radially decomposed as a series of slightly
overlapping Gaussian rings, suggesting the presence of unresolved gaps or dips.
The dip closest to the disk center lies at a radius very close to the hot spot
location at ~AU. The CO excitation conditions indicate that the
outer disk remains in the shadow of the ring. The hot spot probably results
from local heating processes. The two latter points reinforce the hypothesis
that the hot spot is created by an embedded proto-planet shepherding the outer
disk.Comment: 8 pages, 4 figures. Accepted by Ap
Detection of CO(3-2) Emission at z=2.64 from the Gravitationally Lensed Quasar MG 0414+0534
We have detected CO(3-2) line emission from the gravitationally lensed quasar
MG 0414+0534 at redshift 2.64, using the IRAM Plateau de Bure Interferometer.
The line is broad, with Delta v_FWHM = 580 km/s. The velocity-integrated CO
flux is comparable to, but somewhat smaller than, that of IRAS F10214+4724 and
the Cloverleaf quasar (H1413+117), both of which are at similar redshifts. The
lensed components A1+A2 and B were resolved, and separate spectra are presented
for each. We also observed the unlensed radio quiet quasar PG 1634+706 at
z=1.33, finding no significant CO emission.Comment: To be published in ApJ Letters. 9 pages of text in Latex, using style
file aaspp4.sty (included), plus two ps figures to be printed separatel