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Optical Characterization of A New Young Stellar Population in the Serpens Molecular Cloud

Oliveira, Isa and Merín, Bruno and Pontoppidan, Klaus M. and van Dishoeck, Ewine F. and Overzier, Roderik A. and Hernández, Jesús and Sicilia-Aguilar, Aurora and Eiroa, Carlos and Montesinos, Benjamin (2009) Optical Characterization of A New Young Stellar Population in the Serpens Molecular Cloud. Astrophysical Journal, 691 (1). pp. 672-686. ISSN 0004-637X.

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We report on the results of an optical spectroscopic survey designed to confirm the youth and determine the spectral types among a sample of young stellar object (YSO) candidates in the Serpens molecular cloud. We observed 150 infrared (IR) excess objects previously discovered by the Spitzer Legacy Program "From Molecular Cores to Planet-Forming Disks" (c2d), bright enough for subsequent Spitzer/InfraRed Spectrograph (IRS) spectroscopy. We obtained 78 optical spectra of sufficient signal-to-noise for analysis. Extinctions, effective temperatures, and luminosities are estimated for this sample, and used to construct Hertzsprung-Russell (H-R) diagrams for the population. We identified 20 background giants contaminating the sample, based on their relatively high extinction, position in the H-R diagram, the lack of Hα emission and relatively low IR excess. Such strong background contamination (25%) is consistent with the location of Serpens being close to the Galactic plane (5° Galactic latitude). The remaining 58 stars (75%) were all confirmed to be young, mostly K- and M-type stars that are presumed to belong to the cloud. Individual ages and masses for the YSOs are inferred based on theoretical evolutionary models. The models indicate a spread in stellar ages from 1 Myr to 15 Myr, peaking at 2-6 Myr, and a mass distribution of 0.2-1.2 M☉ with median value around 0.8 M☉. Strong Hα emission lines (EW[Hα] > 3 Å) have been detected in more than half of the sample (35 stars). The mass accretion rates as derived from the Hα line widths span a broad distribution over four orders of magnitude with median accretion rate of 10^–8 M☉ yr^–1. Our analysis shows that the majority of the IR excess objects detected in Serpens are actively accreting, young T-Tauri stars.

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Pontoppidan, Klaus M.0000-0001-7552-1562
van Dishoeck, Ewine F.0000-0001-7591-1907
Additional Information:© 2009. The American Astronomical Society. Received 2008 May 20; accepted 2008 September 30; published 2009 January 16. Print publication: Issue 1 (2009 January 20). Support for this work, part of the Spitzer Space Telescope Legacy Science Program, was provided by NASA through Contract Numbers 1256316, 1224608, and 1230780 issued by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407 and by the Spanish Grant AYA 2005-0954. Astrochemistry at Leiden is supported by a Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) Spinoza and Nederlandse Onderzoekschool voor de Astronomie (NOVA) grants and by the European Research Training Network "The Origin of Planetary Systems" (PLANETS, Contract number HPRN-CT-2002-00308). Support to K.M.P was provided by NASA through Hubble Fellowship grant #01201.01, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. The authors thank N. J. Evans II, L. Spezzi, J. Alcalá, G. Herczeg, J. Falcón-Barroso, D. Barrado y Navascues, and A. Bayo for helpful comments and suggestions on earlier versions of the manuscript.
Funding AgencyGrant Number
Ministerio de Educación y Ciencia (MEC)AYA 2005-0954
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
Nederlandse Onderzoekschool voor de Astronomie (NOVA)UNSPECIFIED
European Research Training NetworkHPRN-CT-2002-00308
NASA Hubble Fellowship01201.01
NASANAS 5-26555
Space Telescope Science InstituteUNSPECIFIED
Subject Keywords:Hertzsprung-Russell diagram; ISM: individual (Serpens); planetary systems: protoplanetary disks; stars: pre-main sequence
Issue or Number:1
Record Number:CaltechAUTHORS:OLIapj09
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13111
Deposited By: Archive Administrator
Deposited On:21 Jan 2009 21:45
Last Modified:03 Oct 2019 00:34

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