Astron. Astrophys. 361, 660-670 (2000)

Young stellar clusters and H₂ nebulosities in S233IR ^* **

A. Porras ¹, I. Cruz-González ² and L. Salas <sup>3

1</sup> Instituto Nacional de Astrofísica, Optica y Electrónica, Apartado Postal 216, Puebla, Pue. 72000, México (aporras@inaoep.mx)
² Instituto de Astronomía, UNAM, Apartado Postal 70-264, C.U., México, D.F. 04510, México (irene@astroscu.unam.mx)
³ Instituto de Astronomía, UNAM, Apartado Postal 877, Ensenada, B.C. 22830, México (salas@astrosen.unam.mx)

Received 11 January 2000 / Accepted 30 June 2000

Abstract

We present an infrared photometric study of the star formation region associated to IRAS 05358+3543, hereafter designated S233IR. Several manifestations of star formation activity are present in S233IR: masers, molecular outflow, GMC core, YSOs, young stellar clusters and an IRAS source. The paper includes photometric J, H, K and H₂ (2.12 µm) images and scanning Fabry-Perot observations to study H₂ kinematics. In the 3.6´3.6´ observed field, two distinct young stellar clusters separated by 0.5 pc are found, one being much redder than the other by A_V  7 mag. A collection of PMS objects and several H₂ nebulosities associated to the younger and redder NE cluster are found. Two deeply embedded jet/counter-jet structures, produced by shocked H₂ gas, are detected near the core of the molecular outflow. Possible exciting source candidates of the molecular outflow and H₂ nebula are discussed. The velocity field of H₂ gas shows that the bulk of the emission occurs within -36.9 to 2.3 km/s. Individual spectra of H₂ nebulosities show peak velocities consistent with the rest velocity of the GMC and H₂O maser peak velocities. Luminosity function histograms are used to obtain a crude age estimate for cluster and field stars: 2 Myr for NE cluster, 3 Myr for SW cluster and 6 Myr for field (distributed population) stars; indicating at least two star formation stages and a distributed population of young stars. Finally, from PMS isochrones and NIR photometry, taking care of completeness limits, we estimate stellar masses to study the IMF. A turnover for low-mass-stars is found for the SW cluster, while field stars show a Salpeter IMF.

Key words: stars: early-type stars: formation stars: mass-loss ISM: individual objects: S233IR ISM: jets and outflows

* Based on observations obtained at the Observatorio Astronómico Nacional at San Pedro Mártir, B.C., México.
** Table 1 is only available in electronic form at the CDS via anonymous ftp to ftp://cdsarc.u-strasbg.fr/pub/cats/J/A+A/361/660 (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/361/660

Send offprint requests to: I. Cruz-González

Correspondence to: irene@astroscu.unam.mx

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations
  • 2.1. Direct imaging
  • 2.2. Infrared Fabry-Perot
• 3. Photometry and results
  • 3.1. Stellar photometry routines
  • 3.2. Color-color diagram
  • 3.3. Extinction
• 4. Molecular hydrogen
  • 4.1. Morphology of H₂ nebulosities
  • 4.2. H₂ velocity field
• 5. Discussion
  • 5.1. Two young stellar clusters (YSCs) and molecular outflow
  • 5.2. Age estimation
  • 5.3. Isochrones in the J/J-H diagram
  • 5.4. IMF
• 6. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: October 2, 2000
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