The Properties of X-Ray Luminous Young Stellar Objects in the NGC 1333 and Serpens Embedded Clusters

Abstract

We present new Chandra X-ray data of the NGC 1333 embedded cluster and combine these data with existing Chandra data, Sptizer photometry and ground based spectroscopy of both the NGC 1333 and Serpens Cloud Core clusters to perform a detailed study of the X-ray properties of two of the nearest embedded clusters to the Sun.We first present new, deeper observations of NGC 1333 with Chandra ACIS-I and combine these with existing Spitzer observations of the region. In NGC 1333, a total of 95 cluster members are detected in X-rays, of which 54 were previously identified in the Spitzer data. Of the Spitzer identified sources, we detected 23% of the Class I protostars, 53% of the Flat Spectrum sources, 52% of the Class II, and 50% of the Transition Disk young stellar objects (YSO). Forty-one -2 -Class III members of the cluster are identified, bringing the total identified YSO population to 178.The X-ray Luminosity Functions (XLFs) of the NGC 1333 and Serpens clusters are compared to each other and the Orion Nebula Cluster. Based on a comparison of the XLFs of the Serpens and NGC 1333 clusters to the previously published ONC, we obtain a new distance for the Serpens cluster of 360 +22 −13 pc. Using our previously published spectral types, effective temperatures and bolometric luminosities, we analyze the dependence of the X-ray emission on the measured stellar properties. The X-ray luminosity was found to depend on the calculated bolometric luminosity as in previous studies of other clusters. We examine the dependence of L X on stellar surface area and effective temperature, and find that L X depends primarily on the stellar surface area. In the NGC 1333 cluster, the Class III sources have a somewhat higher X-ray luminosity for a given surface area. We also find evidence in NGC 1333 for a jump in the X-ray luminosity between spectral types of M0 and K7, we speculate that this may result from the presence of radiative zones in the K-stars.The gas column density vs. extinction in the NGC 1333 parental molecular cloud was examined using the Hydrogen column density determined from the X-ray absorption to the embedded stars and the K-band extinction measured to those stars. In NGC 1333, we find N H = 0.89 ± 0.13 × 10 22 A K , this is lower than expected of the standard ISM but similar to that found previously in the Serpens Cloud Core.

First stars of theρOphiuchi dark cloud

“…The average N H /A V ratio near ρ Ophiuchi is lower than in Orion or the typical ISM value, and slightly higher than the values of N H /A V found in other low mass star forming regions like NGC 1333, Serpens and L1641 (Winston et al 2007(Winston et al , 2010Pillitteri et al 2013). This evidence could be related to different amounts of ambient UV fluxes.…”

The Gould’s Belt Very Large Array Survey. Ii. The Serpens Region

“…On the other hand, Bontemps et al (2010) argue that the W40 region, the Aquila rift, and Serpens Main are parts of the same star-forming region, located at a common distance of 260 pc. However, more recently, based on a comparison of the X-ray luminosity function of the Serpens cluster with the previously published Orion Nebula cluster, Winston et al (2010) obtained a new distance for the Serpens core of -+…”

A SPITZER IRS SURVEY OF NGC 1333: INSIGHTS INTO DISK EVOLUTION FROM A VERY YOUNG CLUSTER

“…in the mid-infrared and have been found in NGC 1333 through X-ray surveys (Getman et al 2002;Winston et al 2009Winston et al , 2010.…”

“…In the study of NGC 1333 Xray sources by Winston et al (2010), they found 41 Class III objects in their 95-object sample (43%). Winston et al (2010) selected for likelihood of X-ray activity, and therefore SED class fractions would be biased toward later stages of star formation that have higher X-ray activity. Gutermuth et al (2008) calculated a disk fraction of NGC 1333 using sources within a circle of radius of 5.…”

“…We observed all objects with detections (σ < 0.2 mag) in the IRAC 8.0 μm band and MIPS 24 μm band that are brighter than 11.54 mag at 8.0 μm and 8.5 mag at 24 μm. For this reason we adopt their identifiers for our sample (these identifiers were also used in Winston et al 2009Winston et al , 2010. The basic data for this sample, namely, [GMM08] SED index, R.A., decl., AOR ID, and alternate names, are listed in Table 1.…”