PROTOPLANETARY DISK EVOLUTION AROUND THE TRIGGERED STAR-FORMING REGION CEPHEUS B

Journal Article · Fri Jul 10 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/699/2/1454; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21333739

Getman, Konstantin V; Feigelson, Eric D; Luhman, Kevin L; Garmire, Gordon P ^[1]; Sicilia-Aguilar, Aurora ^[2]

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1. Department of Astronomy and Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802 (United States)
2. Max-Planck-Institut fur Astronomie, Konigstuhl 17, 69117 Heidelberg (Germany)

The Cepheus B (Cep B) molecular cloud and a portion of the nearby Cep OB3b OB association, one of the most active regions of star formation within 1 kpc, have been observed with the Infrared Array Camera detector on board the Spitzer Space Telescope. The goals are to study protoplanetary disk evolution and processes of sequential triggered star formation in the region. Out of {approx}400 pre-main-sequence (PMS) stars selected with an earlier Chandra X-ray Observatory observation, {approx}95% are identified with mid-infrared sources and most of these are classified as diskless or disk-bearing stars. The discovery of the additional >200 IR-excess low-mass members gives a combined Chandra+Spitzer PMS sample that is almost complete down to 0.5 M{sub sun} outside of the cloud, and somewhat above 1 M{sub sun} in the cloud. Analyses of the nearly disk-unbiased combined Chandra and Spitzer-selected stellar sample give several results. Our major finding is a spatio-temporal gradient of young stars from the hot molecular core toward the primary ionizing O star HD 217086. This strongly supports the radiation-driven implosion (RDI) model of triggered star formation in the region. The empirical estimate for the shock velocity of {approx}1 km s{sup -1} is very similar to theoretical models of RDI in shocked molecular clouds. The initial mass function (IMF) of the lightly obscured triggered population exhibits a standard Galactic field IMF shape. The unusually high apparent value of {approx}>70% star formation efficiency inferred from the ratio of star mass to current molecular gas mass indicates that most of the Cep B molecular cloud has been already ablated or transformed to stars. Contrary to the current RDI simulations, our findings indicate that star formation triggering by H II region shocks is not restricted to a single episode but can continue for millions of years. Other results include: (1) agreement of the disk fractions, their mass dependency, and fractions of transition disks with other clusters; (2) confirmation of the youthfulness of the embedded Cep B cluster; (3) confirmation of the effect of suppression of time-integrated X-ray emission in disk-bearing versus diskless systems.

• OSTI ID: 21333739
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 699; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
EMISSION
IMPLOSIONS
MASS
PROTOPLANETS
SIMULATION
STAR EVOLUTION
STARS
TELESCOPES