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

Konstantin V. Getman (Lead / Corresponding author), Eric D. Feigelson, Kevin L. Luhman, Aurora Sicilia-Aguilar, Junfeng Wang, Gordon P. Garmire

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

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 similar to 400 pre-main-sequence (PMS) stars selected with an earlier Chandra X-ray Observatory observation, similar to 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(circle dot) outside of the cloud, and somewhat above 1 M(circle dot) in the cloud. Analyses of the nearly disk-ubiased 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 similar to 1 km s(-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 greater than or similar to 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.
Original languageEnglish
Pages (from-to)1454-1472
Number of pages19
JournalAstrophysical Journal
Volume699
Issue number2
DOIs
Publication statusPublished - 23 Jun 2009

Keywords

  • ISM: individual (Cepheus B cloud) open clusters and associations: individual (Cepheus OB3) planetary systems: protoplanetary disks stars: formation stars: pre-main sequence X-rays: stars BRIGHT-RIMMED CLOUDS SPITZER-SPACE-TELESCOPE RADIATION-DRIVEN IMPLOSION INFRARED ARRAY CAMERA X-RAY-EMISSION T-TAURI STARS ORION ULTRADEEP PROJECT INTERMEDIATE-MASS STARS NEWTON EXTENDED SURVEY YOUNG STELLAR OBJECTS

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