The 24 Micron View of Embedded Star Formation in NGC 7129

Abstract

We present observations of the star formation region NGC 7129 taken with the Multiband Imaging Photometer for Spitzer (MIPS). A significant population of sources, likely pre-main sequence members of the young stellar cluster, is revealed outside the central photoionization region. Combining with Infrared Array Camera (IRAC) and ground-based near-infrared images, we have obtained colors and spectral energy distributions for some 60 objects. The [3.6]-[4.5] vs.[8]- [24] color-color plane shows sources clustered at several different loci, which roughly correspond to the archetypal evolutionary sequence Class 0, I, II, and III. We obtain preliminary classifications for 36 objects, and find significant numbers of both Class I and II objects. Most of the pre-main sequence candidates are associated with the densest part of the molecular cloud surrounding the photoionization region, indicating active star formation over a broad area outside the central cluster. We discuss three Class II candidates that exhibit evidence of inner disk clearing, which would be some of the youngest known examples of a transition from accretion to optically thin quiescent disks.

Initial Results from the Spitzer Young Stellar Cluster Survey

“…These data provide an independent check of our classification using the IRAC color plane. For the 24 sources common to both samples (Muzerolle et al required detection in three IRAC bands and the MIPS 24 m band), the classification by Muzerolle et al (2004) is almost entirely consistent with ours (see NGC 7129 plot in Fig. 1).…”

“…Background planetary nebulae, asymptotic giant branch (AGB) stars, and galaxies may also be misidentified as young stars or protostars (Whitney et al 2003); however, the spatial distribution of sources discussed in x 4 indicates that the amount of background contamination is small. By combining MIPS 24 m photometry with the IRAC photometry of NGC 7129, Muzerolle et al (2004) identify Class I and Class II objects in NGC 7129 by using the slope of the 1-24 m SEDs. These data provide an independent check of our classification using the IRAC color plane.…”

“…The vectors were calculated for Vega (at position 0, 0), a young star with disk taken from the models of P. D'Alessio et al (2004, in preparation) (0.2, 0.5), and a flat spectrum source (0.73, 1). Twenty-four sources in NGC 7129 were classified using IRAC photometry combined with MIPS 24 m photometry by Muzerolle et al (2004); to display these classifications, we superpose a plus sign for Class I objects and a cross for Class II objects. The error bars in the Cep C plot show the median uncertainty in the colors for all the sources in all four clusters.…”

“…Emission in 13 CO is detected toward all but three of these sources: the northernmost Class I object is outside the 13 CO map, and no molecular gas is detected toward the two Class I objects west of the reflection nebula. Gutermuth et al (2004) and Muzerolle et al (2004) discuss IRAC and MIPS observations of NGC 7129 in more detail.…”

Disk Evolution in Cep OB2: Results from theSpitzer Space Telescope

“…In the fourth panel we also show the region of observed excesses in the young cluster NGC 7129 from Muzerolle et al (2004) as a dot-dashed box, indicating general agreement with our program object colors.…”