J/A+A/559/A82 Sub-mm observations of IRS43 and IRS63 (Brinch+, 2013)
Interplay between chemistry and dynamics in embedded protostellar disks.
Brinch C., Jorgensen J.K.
<Astron. Astrophys. 559, A82 (2013)>
=2013A&A...559A..82B 2013A&A...559A..82B
ADC_Keywords: Infrared sources ; YSOs ; Millimetric/submm sources
Keywords: stars: formation - stars: pre-main sequence -
circumstellar matter - radiation transfer - submillimeter: stars
Abstract:
A fundamental part of the study of star formation is to place young
stellar objects in an evolutionary sequence. Establishing a robust
evolutionary classification scheme allows us not only to understand
how the Sun was born but also to predict what kind of main sequence
star a given protostar will become. Traditionally, low-mass young
stellar objects are classified according to the shape of their
spectral energy distributions. Such methods are, however, prone to
misclassification due to degeneracy and do not constrain the temporal
evolution. More recently, young stellar objects have been classified
based on envelope, disk, and stellar masses determined from resolved
images of their continuum and line emission at submillimeter
wavelengths.
Through detailed modeling of two Class I sources, we aim at
determining accurate velocity profiles and explore the role of
freeze-out chemistry in such objects.
We present new Submillimeter Array observations of the continuum and
HCO+ line emission at 1.1mm toward two protostars, IRS 63 and IRS 43
in the Ophiuchus star forming region. The sources were modeled in
detail using dust radiation transfer to fit the SED and continuum
images and line radiation transfer to produce synthetic
position-velocity diagrams. We used a chi2 search algorithm to find
the best model fit to the data and to estimate the errors in the model
variables.
Our best fit models present disk, envelope, and stellar masses, as
well as the HCO+ abundance and inclination of both sources. We also
identify a ring structure with a radius of about 200AU in IRS 63.
Conclusions. We find that freeze-out chemistry is important in IRS 63
but not for IRS 43. We show that the velocity field in IRS 43 is
consistent with Keplerian rotation. Owing molecular depletion, it is
not possible to draw a similar conclusion for IRS 63. We identify a
ring-shaped structure in IRS 63 on the same spatial scale as the disk
outer radius. No such structure is seen in IRS 43.
We find that freeze-out chemistry is important in IRS 63 but not for
IRS 43. We show that the velocity field in IRS 43 is consistent with
Keplerian rotation. Owing molecular depletion, it is not possible to
draw a similar conclusion for IRS 63. We identify a ring-shaped
structure in IRS 63 on the same spatial scale as the disk outer
radius. No such structure is seen in IRS 43.
Description:
Reduced, and combined, Submillimeter Array (com + ext conf.)
observations at 267GHz of IRS 43 and IRS 63. Raw data are available
through the SMA archive.
Objects:
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RA (2000) DE Designation(s)
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16 27 26.94 -24 40 50.8 IRS 43 = WLY 2-43
16 31 35.65 -24 01 29.3 IRS 63 = WLY 2-63
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 143 4 List of FITS images and datacubes
images/* . 4 Individual images and datacubes
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 F3.1 arcsec/pix Scale Scale of the image (0.3arcsec/pix)
24- 25 I2 pix Nx [51/55] Number of pixels along X-axis
26 A1 --- --- [x]
27- 28 I2 pix Ny [51/55] Number of pixels along Y-axis
29 A1 --- --- [x]
30- 32 I3 pix Nz [512]? Number of velocity points
34- 41 F8.1 km/s Vlsrl ? Lower value of Vlsr interval
for spectral image cubes
43- 49 F7.1 km/s Vlsru ? Upper value of Vlsr interval
for spectral image cubes
51- 57 F7.3 km/s dVlsr ? Velocity step for spectral image cubes
59- 68 F10.6 GHz Freq ? LSR frequency of continuum images
71- 98 A28 --- FileName Name of FITS file in subdirectory images
99-143 A45 --- Title Title of the images
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Acknowledgements:
Christian Brinch, brinch(at)nbi.dk
(End) Patricia Vannier [CDS] 30-Sep-2013