166 research outputs found
The Bok Globule BHR 160: structure and star formation
BHR 160 is a virtually unstudied cometary globule within the Sco OB4
association in Scorpius at a distance of 1600pc. It is part of a system of
cometary clouds which face the luminous O star HD155806. BHR 160 is special
because it has an intense bright rim. We attempt to derive physical parameters
for BHR 160 and to understand its structure and the origin of its peculiar
bright rim. BHR 160 was mapped in the CO, CO and CO (2-1)
and (1-0) and CS (3-2) and (2-1) lines. These data, augmented with stellar
photometry derived from the ESO VVV survey, were used to derive the mass and
distribution of molecular material in BHR 160 and its surroundings. Archival
mid-infrared data from the WISE satellite was used to find IR excess stars in
the globule and its neighbourhood. An elongated 1' by 0.6' core lies adjacent
to the globule bright rim. CO emission covers the whole globule, but the
CO, CO and CS emission is more concentrated to the core. The
CO line profiles indicate the presence of outflowing material near the
core, but the spatial resolution of the mm data is not sufficient for a
detailed spatial analysis. The BHR 160 mass estimated from the CO
mapping is 10050Msun(d/1.6kpc) where d is the distance to the globule.
Approximately 70 percent of the mass lies in the dense core. The total mass of
molecular gas in the direction of BHR 160 is 210(d/1.6kpc) Msun when
estimated from the more extended VVV NIR photometry. We argue that the bright
rim of BHR 160 is produced by a close-by early B-type star, HD 319648, that was
likely recently born in the globule. This star is likely to have triggered the
formation of a source, IRS 1, that is embedded within the core of the globule
and detected only in Ks and by WISE and IRAS.Comment: 19 pages, 24 figures, Accepted for publication in Astronomy and
Astrophysic
Halpha emission-line stars in molecular clouds. II. The M42 region
We present a deep survey of Halpha emission-line stars in the M42 region
using wide-field objective prism films. A total of 1699 Halpha emission-line
stars were identified, of which 1025 were previously unknown, within an area of
5.5 x 5.5 degrees centred on the Trapezium Cluster. We present Halpha strength
estimates, positions, and JHKs photometry extracted from 2MASS, and comparisons
to previous surveys. The spatial distribution of the bulk of the stars follows
the molecular cloud as seen in CO and these stars are likely to belong to the
very young population of stars associated with the Orion Nebula Cluster.
Additionally, there is a scattered population of Halpha emission-line stars
distributed all over the region surveyed, which may consist partly of
foreground stars associated with the young NGC 1980 cluster, as well as some
foreground and background dMe or Be stars. The present catalogue adds a large
number of candidate low-mass young stars belonging to the Orion population,
selected independently of their infrared excess or X-ray emission.Comment: 38 pages, 18 figures. Published in Astronomy & Astrophysics v3: chart
for ESO-HA 1639 corrected. Typos in Table 2 corrected. Photometry for ESO-HA
1639 in Table 2 correcte
The star formation environment of the FU Ori type star V582 Aur
We have studied the environment of the FU Ori type star V582 Aur. Our aim is
to explore the star-forming region associated with this young eruptive star.
Using slitless spectroscopy we searched for H alpha emission stars within a
field of 11.5arcmin \times 11.5arcmin, centred on V582 Aur. Based on UKIDSS and
Spitzer Space Telescope data we further selected infrared-excess young stellar
object candidates. In all, we identified 68 candidate low-mass young stars, 16
of which exhibited H alpha emission in the slitless spectroscopic images. The
colour-magnitude diagram of the selected objects, based on IPHAS data, suggests
that they are low-mass pre-main-sequence stars associated with the Aur OB 1
association, located at a distance of 1.3 kpc from the Sun. The bright-rimmed
globules in the local environment of V582 Aur probably belong to the dark cloud
LDN~1516. Our results suggest that star formation in these globules might have
been triggered by the radiation field of a few hot members of Aur OB 1. The
bolometric luminosity of V582 Aur, based on archival photometric data and on
the adopted distance, is 150-320 Lsun.Comment: 10 pages, 8 figures, 3 tables. Accepted for publication by MNRA
High Resolution Near-Infrared Spectroscopy of FUors and FUor-like stars
We present new high resolution (R=18,000) near-infrared spectroscopic
observations of a sample of classical FU Orionis stars (FUors) and other young
stars with FUor characteristics that are sources of Herbig-Haro flows. Spectra
are presented for the region 2.203 - 2.236 microns which is rich in absorption
lines sensitive to both effective temperatures and surface gravities of stars.
Both FUors and FUor-like stars show numerous broad and weak unidentified
spectral features in this region. Spectra of the 2.280 - 2.300 micron region
are also presented, with the 2.2935 micron v=2-0 CO absorption bandhead being
clearly the strongest feature seen in the spectra all FUors and Fuor-like
stars. A cross-correlation analysis shows that FUor and FUor-like spectra in
the 2.203 - 2.236 micron region are not consistent with late-type dwarfs,
giants, nor embedded protostars. The cross-correlations also show that the
observed FUor-like Herbig-Haro energy sources have spectra that are
substantively similar to those of FUors. Both object groups also have similar
near-infrared colors. The large line widths and double-peaked nature of the
spectra of the FUor-like stars are consistent with the established accretion
disk model for FUors, also consistent with their near-infrared colors. It
appears that young stars with FUor-like characteristics may be more common than
projected from the relatively few known classical FUors.Comment: 21 pages, 4 figures, accepted by The Astronomical Journa
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