A combined Spitzer and Chandra survey of young stellar objects in the Serpens cloud core.
WINSTON E., MEGEATH S.T., WOLK S.J., MUZEROLLE J., GUTERMUTH R., HORA J.L., ALLEN L.E., SPITZBART B., MYERS P. and FAZIO G.G.
Abstract (from CDS):
We present Spitzer and Chandra observations of the nearby (∼260 pc) embedded stellar cluster in the Serpens cloud core. We observed, using Spitzer's IRAC and MIPS instruments, in six wavelength bands from 3 to 70 µm, to detect thermal emission from circumstellar disks and protostellar envelopes and to classify stars using color-color diagrams and SEDs. These data are combined with Chandra observations to examine the effects of circumstellar disks on stellar X-ray properties. Young diskless stars were also identified from their increased X-ray emission. We have identified 138 YSOs in Serpens: 22 Class 0/I, 16 flat-spectrum, 62 Class II, 17 transition disk, and 21 Class III stars; 60 of these exhibit X-ray emission. Our primary results are the following: (1) 10 protostars detected previously in the submillimeter are detected at λ<24 µm, seven at λ<8 µm; (2) the protostars are more closely grouped than more evolved YSOs (median protostar separation ∼0.024 pc); and (3) the luminosity and temperature of the X-ray-emitting plasma around these YSOs do not show any significant dependence on evolutionary class. We combine the infrared-derived values of AK and X-ray values of NH for eight Class III objects and find that the column density of hydrogen gas per magnitude of extinctions is less than half the standard interstellar value, for AK>1. This may be the result of grain growth through coagulation and/or the accretion of volatiles in the Serpens cloud core.