EDP Sciences
Free access
Issue
A&A
Volume 423, Number 2, August IV 2004
Page(s) 629 - 641
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20047173


A&A 423, 629-641 (2004)
DOI: 10.1051/0004-6361:20047173

A search for shock-excited molecular hydrogen knots in Chamaeleon I very low mass YSOs

M. Gómez1, P. Persi2, A. R. Marenzi2, M. Roth3 and M. Tapia4

1  Observatorio Astronómico de Córdoba, Laprida 854, 5000 Córdoba, Argentina
    e-mail: mercedes@oac.uncor.edu
2  Istituto Astrofisica Spaziale e Fisica Cosmica, CNR, Via del Fosso del Cavaliere, 00133 Roma, Italia
    e-mail: [persi ;marenzi]@rm.iasf.cnr.it
3  Las Campanas Observatory, Carnegie Institution of Washington, Casilla 601, La Serena, Chile
    e-mail: miguel@lco.cl
4  Instituto de Astronomía, UNAM, Apartado Postal 877, Ensenada, Baja California, CP 22830, Mexico
    e-mail: mt@astrosen.unam.mx

(Received 30 January 2004 / Accepted 3 May 2004)

Abstract
We have obtained narrow-band images of three selected areas of the Chamaeleon I dark cloud which harbor very low mass young stars, centered on the H 2 and Br $\gamma$ lines and neighboring continuum as well as on the broad band  $K_{\rm s}$. One region is located in the northern part of the cloud, roughly coinciding with the densest area. The other two regions are in the southern section of the cloud. Our aim is to search for H 2 outflows associated with these objects. In the northern region, we found seven new H 2 knots, five of which are aligned in the direction of a previously known 12CO molecular bipolar outflow. Further evidence that the class I low mass stellar object ISO-ChaI 192 is the driving source of the molecular flow is given by the presence of a 960 AU long elongated structure at 2.2  $\mu$m emanating from this star and oriented parallel to the bipolar structure. Another pair of H 2 knots, although lying relatively nearby, is not aligned with the outflow direction. They are located on opposite sides of C1-6, a low mass class II object in the northern part of the Chamaeleon I dark cloud. In contrast, we fail to detect any H 2 emission object brighter than our sensitivity limit (~ $6 \times 10^{-32}$ W/m 2 Hz arcsec 2) in the two southern areas of the cloud that also harbor several very low mass stars, including two transition stellar/sub-stellar objects. This negative result is probably not surprising in view of the extremely low accretion rates measured for brown dwarfs ( $\dot{M} \sim 10^{-12} {-}10^{-9} ~ M_{\odot}$ yr -1). Deeper H 2 observations are required to better constraint the outflow event in sub-stellar objects.


Key words: stars: formation -- stars: low-mass, brown dwarfs -- ISM: jets and outflows -- ISM: individual objects: Chamaeleon I

SIMBAD Objects



© ESO 2004