A Combined Spitzer and Chandra Survey of Young Stellar Objects in the Serpens Cloud Core

TL;DR

This study combines Spitzer and Chandra observations to classify and analyze young stellar objects in the Serpens Cloud Core, revealing their spatial distribution, X-ray properties, and implications for dust grain growth.

Contribution

First combined infrared and X-ray survey of Serpens YSOs, providing new insights into their distribution, properties, and dust grain evolution.

Findings

Protostars are more closely grouped than evolved YSOs.

X-ray plasma properties do not depend on evolutionary class.

Hydrogen column density per magnitude of extinction is lower than interstellar standard.

Abstract

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 ${\mu}m$, to detect thermal emission from circumstellar disks and protostellar envelopes, and to classify stars using color-color diagrams and spectral energy distributions (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 which exhibit X-ray emission. Our primary results are the following: 1.) ten protostars detected previously in the sub-millimeter are detected at lambda < 24 microns, seven at lambda < 8 microns, 2.) the protostars are more closely grouped than more evolved YSOs (median separation : ~0.024 pc, and 3.) the luminosity and temperature of the X-ray emitting plasma around these YSOs does not show any significant dependence on evolutionary class. We combine the infrared derived values of AK and X-ray values of NH for 8 class III objects and find that the column density of hydrogen gas per mag 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.