Astronomy and Astrophysics, volume 421, 623-642 (2004/7-2)
The young stellar population in the Serpens Cloud Core: An ISOCAM survey.
KAAS A.A., OLOFSSON G., BONTEMPS S., ANDRE P., NORDH L., HULDTGREN M., PRUSTI T., PERSI P., DELGADO A.J., MOTTE F., ABERGEL A., BOULANGER F., BURGDORF M., CASALI M.M., CESARSKY C.J., DAVIES J., FALGARONE E., MONTMERLE T., PERAULT M., PUGET J.L. and SIBILLE F.
Abstract (from CDS):
We present results from an ISOCAM survey in the two broad band filters LW2 (5-8.5µm) and LW3 (12-18µm) of a 0.13 square degree coverage of the Serpens Main Cloud Core. A total of 392 sources were detected in the 6.7µm band and 139 in the 14.3µm band to a limiting sensitivity of ∼2mJy. We identified 53 Young Stellar Objects (YSOs) with mid-IR excess from the single colour index [14.3/6.7], and 8 additional YSOs from the H-K/K-m6.7 diagram. Only 32 of these 61 sources were previously known to be YSO candidates. Only about 50% of the mid-IR excess sources show excesses in the near-IR J-H/H-K diagram. In the 48 square arcmin field covering the central Cloud Core the ClassI/ClassII number ratio is 19/18, i.e. about 10 times larger than in other young embedded clusters such as ρ Ophiuchi or Chamaeleon. The mid-IR fluxes of the ClassI and flat-spectrum sources are found to be on the average larger than those of ClassII sources. Stellar luminosities are estimated for the ClassII sample, and its luminosity function is compatible with a coeval population of about 2Myr which follows a three segment power-law IMF. For this age about 20% of the ClassIIs are found to be young brown dwarf candidates. The YSOs are in general strongly clustered, the ClassI sources more than the ClassII sources, and there is an indication of sub-clustering. The sub-clustering of the protostar candidates has a spatial scale of 0.12pc. These sub-clusters are found along the NW-SE oriented ridge and in very good agreement with the location of dense cores traced by millimeter data. The smallest clustering scale for the ClassII sources is about 0.25pc, similar to what was found for ρ Ophiuchi. Our data show evidence that star formation in Serpens has proceeded in several phases, and that a ``microburst'' of star formation has taken place very recently, probably within the last 105yrs.
stars: formation - stars: pre-main-sequence - stars: luminosity function, mass function - stars: low-mass, brown dwarfs - ISM: individual objects: Serpens Cloud Core
VizieR on-line data:
<Available at CDS (J/A+A/421/623): table2.dat table3.dat>
Tables 2,3: [KOB2004] NNNa N=77+71.
Fig. 11 : FIRS1 = [HWJ84] FIRS 1 (RA of [HWJ84] does not coincide with location in Fig.11), SMM N = [CED93] N.
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