The Young Stellar Population of Lynds 1340. An Infrared View

Abstract

We present results of an infrared study of the molecular cloud Lynds 1340, forming three groups of low-and intermediate-mass stars. Our goals are to identify and characterize the young stellar population of the cloud, study the relationships between the properties of the cloud and the emergent stellar groups, and integrate L1340 into the picture of the star-forming activity of our Galactic environment. We selected candidate young stellar objects (YSOs) from the Spitzer and WISE databases using various published color criteria and classified them based on the slope of the spectral energy distribution (SED). We identified 170 Class II, 27 flat SED, and 45 Class 0/I sources. High angular resolution near-infrared observations of the RNO 7 cluster, embedded in L1340, revealed eight new young stars of near-infrared excess. The surface density distribution of YSOs shows three groups, associated with the three major molecular clumps of L1340, each consisting of 100 members, including both premain-sequence stars and embedded protostars. New Herbig-Haro objects were identified in the Spitzer images. Our results demonstrate that L1340 is a prolific star-forming region of our Galactic environment in which several specific properties of the intermediate-mass mode of star formation can be studied in detail.

Protostellar Outflows in L1340

“…After inspection of the large scale structure of the outflow and of the WISE 3.4µm, 4.6µm, 12µm, & 22µm images we conclude that the source of the flow is not in the region suggested by Kumar et al (2002), but that it lies 1.6-1.8 to the southeast along the flow axis and that the flow is driven by either SSTSL2 J022820.81+723500.5 or SSTSL2 J022818.51+723506.2. We prefer this as the source region (similar to the conclusion of Kun et al 2016b) instead of that suggested by Kumar et al (2002) because these two candidate source stars were both classified as Class 0/I by Kun et al (2016b) and SSTSL2 J022820.81+723500.5 was discussed as a candidate Class 0 source. In addition, the filamentary H 2 structure around these two sources (MHO 2928 G) passes through the sources themselves and could plausibly be a jet, unlike the filament (MHO 2928 B) south of the Kumar et al (2002) source star.…”

“…Kumar et al (2002) suggested that the flow was launched from a star which corresponds to SSTSL2 J022759.92+723556.4, a probable double star. Kun et al (2016b) catalog it as a flat SED source, but note that the SED "results from the composite fluxes of the central objects". This region is very complex and Kumar et al (2002) identified two candidate jets in Hα and [Sii] emerging from two stars (which they designated S1 and S2) separated by about 2 arcseconds at position angles of 320 and 275 degrees respectively.…”

“…The southern star is SSTSL2 J022844.40+723533.5 and the northern is SSTSL2 J022842.57+723544.3. Both were classified by Kun et al (2016b) as Class 0/I sourced based on their SED slopes. IRAS F02238+7222 (identified by Kumar et al 2002 as a candidate young star) also lies along the axis of the flow, however we find no sources in the WISE images or in our near-IR images which seem to correspond to IRAS F02238+7222.…”

“…Using infrared photometry, Kun et al (2016b) identified and classified 170 Class II, 27 flat SED, and 45 Class 0/I protostars in L1340. They estimated the extinction to each using the results of Kun et al (2016a) and derived bolometric temperatures and luminosities based on the spectral energy distribution (SED) of each protostar.…”

The Intermediate-Mass Star-Forming Region Lynds 1340. An Optical View

“…7 of Luhman et al 2009). The number of Class II YSOs are also similar in both star-forming regions (Luhman et al 2010;Kun et al 2016), whereas they are different in volume, molecular mass and kinetic temperature, structure, and Galactic environment (Kenyon, Gómez, & Whitney 2008). To check whether disk properties observed in the two apparently coeval star-forming regions can be distinguished or not, we collected statistical data in Table 8.…”