The Vulpecula OB association, Vul OB1, is a region of active star formation located in the Galactic plane at 2.3kpc from the Sun. Previous studies suggest that sequential star formation is propagating along this 100pc long molecular complex. In this paper, we use Spitzer MIPSGAL and GLIMPSE data to reconstruct the star formation history of Vul OB1, and search for signatures of past triggering events. We make a census of young stellar objects (YSOs) in Vul OB1 based on IR color and magnitude criteria, and we rely on the properties and nature of these YSOs to trace recent episodes of massive star formation. We find 856 YSO candidates, and show that the evolutionary stage of the YSO population in Vul OB1 is rather homogeneous -ruling out the scenario of propagating star formation. We estimate the current star formation efficiency to be ~8%. We also report the discovery of a dozen pillar-like structures, which are confirmed to be sites of small scale triggered star formation.
The optically bright, extended HII region Sh2-252 is a part of the Gemini OB1 association. This region is mainly composed of two small clusters NGC 2175s and Teu 136 and four CHII regions namely A, B, C and E. In this paper, an extensive survey of the star-forming complex Sh2-252 has been undertaken with an aim to explore its hidden young stellar population, its characteristics, spatial distribution, morphology of the region and finally to understand the star formation scenario of the complex for the first time. Spitzer-IRAC, MIPS photometry (3.6-24um) are combined with 2MASS-NIR and optical data sets to identify and classify the YSOs by their IR excess emission from their circumstellar material. From the well-fit models for each source derived from the SED fitting tool, we calculated the {chi}^2^ weighted model parameters such as the stellar mass (M*), temperature (T*), stellar age (t*), mass of the disc (Mdisc), disc accretion rate (dMdisc/dt), envelope accretion rate (dMenv/dt) presented in table1.dat.
The Sh2-294 H II region ionized by a single B0V star features several infrared excess sources, a photodissociation region, and also a group of reddened stars at its border. The star formation scenario in this region seems to be quite complex. In this paper, we present follow-up results of Sh2-294 H II region at 3.6, 4.5, 5.8, and 8.0{mu}m observed with the Spitzer Space Telescope Infrared Array Camera (IRAC), coupled with H_2_(2.12{mu}m) observation, to characterize the young population of the region and to understand its star formation history. We identified 36 young stellar object (YSO, Class I, Class II, and Class I/II) candidates using IRAC color-color diagrams. It is found that Class I sources are preferentially located at the outskirts of the H II region and associated with enhanced H_2_emission; none of them are located near the central cluster. Combining the optical to mid-infrared (MIR) photometry of the YSO candidates and using the spectral energy distribution fitting models, we constrained stellar parameters and the evolutionary status of 33 YSO candidates. Most of them are interpreted by the model as low-mass (<4 M_{sun}_) YSOs; however, we also detected a massive YSO (~9 M_{sun}_) of Class I nature, embedded in a cloud of visual extinction of ~24 mag.
