J/A+A/472/519 N2H+(1-0) maps of Ophiuchus main cloud (Andre+, 2007)
The initial conditions of star formation in the Ophiuchus main cloud:
Kinematics of the protocluster condensations.
Andre P., Belloche A., Motte F., Peretto N.
<Astron. Astrophys. 472, 519 (2007)>
=2007A&A...472..519A 2007A&A...472..519A (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds
Keywords: stars: formation - stars: circumstellar matter - ISM: clouds -
ISM: structure - ISM : kinematics and dynamics -
Abstract:
The earliest phases of clustered star formation and the origin of the
stellar initial mass function (IMF) are currently much debated. In
order to constrain the origin of the IMF, we investigated the internal
and relative motions of starless condensations and protostars
previously detected by us in the dust continuum at 1.2mm in the L1688
protocluster of the Ophiuchus molecular cloud complex. The starless
condensations have a mass spectrum resembling the IMF and are
therefore likely representative of the initial stages of star
formation in the protocluster.
We carried out detailed molecular line observations, including some
N2H+(1-0) mapping, of the Ophiuchus protocluster condensations using
the IRAM 30m telescope.
We measured subsonic or at most transonic levels of internal
turbulence within the condensations, implying virial masses which
generally agree within a factor of ∼2 with the masses derived from
the 1.2mm dust continuum. This supports the notion that most of the
L1688 starless condensations are gravitationally bound and prestellar
in nature. We measured a global one-dimensional velocity dispersion of
less than 0.4km/s between condensations. This small relative velocity
dispersion implies that, in general, the condensations do not have
time to interact with one another before evolving into
pre-main-sequence objects.
Our observations support the view that the IMF is partly determined by
cloud fragmentation at the prestellar stage. Competitive accretion is
unlikely to be the dominant mechanism at the protostellar stage in the
Ophiuchus protocluster, but it may possibly govern the growth of
starless, self-gravitating condensations initially produced by
gravoturbulent fragmentation toward an IMF, Salpeter-like mass
spectrum.
Description:
N2H+(1-0) data cubes obtained with the IRAM 30m telescope for 6 cores
in the Ophiuchus main cloud (L1688). The following cores were mapped
in the "on-the-fly" mode: OphA, OphB1, OphB2, OphC, OphE, and OphF.
The angular resolution was ∼26" and the spectral resolution was 10kHz
for OphB1 and 20kHz for the other cores.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
object.dat 44 6 Objects position
fits/* . 6 N2H+(1-0) data cube files
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Byte-by-byte Description of file: object.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Object name
9- 10 I2 h RAh Right ascension (J2000.0)
12- 13 I2 min RAm Right ascension (J2000.0)
15- 19 F5.2 s RAs Right ascension (J2000.0)
21 A1 --- DE- Declination sign (J2000.0)
22- 23 I2 deg DEd Declination (J2000.0)
25- 26 I2 arcmin DEm Declination (J2000.0)
28- 31 F4.1 arcsec DEs Declination (J2000.0)
33- 44 A12 --- FileName Name of the FITS data cube file of the line
N2H+(1-0) (93.18GHz) in subdirectory fits
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Acknowledgements:
Philippe Andre
(End) Philippe Andre [CEA, France] 05-Jul-2007