Showing papers by "Brian Babler published in 2019"

Identifying Young Stellar Objects in the Outer Galaxy: l = 224° Region in Canis Major

Abstract: We study a very young star-forming region in the outer Galaxy that is the most concentrated source of outflows in the Spitzer Space Telescope GLIMPSE360 survey. This region, dubbed CMa-l224, is located in the Canis Major OB1 association. CMa-l224 is relatively faint in the mid-infrared, but it shines brightly at the far-infrared wavelengths as revealed by the Herschel Space Observatory data from the Hi-GAL survey. Using the 3.6 and 4.5 $\\mu$m data from the Spitzer/GLIMPSE360 survey, combined with the JHK$_s$ 2MASS and the 70-500 $\\mu$m Herschel/Hi-GAL data, we develop a young stellar object (YSO) selection criteria based on color-color cuts and fitting of the YSO candidates' spectral energy distributions with YSO 2D radiative transfer models. We identify 293 YSO candidates and estimate physical parameters for 210 sources well-fit with YSO models. We select an additional 47 sources with GLIMPSE360-only photometry as `possible YSO candidates'. The vast majority of these sources are associated with high H$_2$ column density regions and are good targets for follow-up studies. The distribution of YSO candidates at different evolutionary stages with respect to Herschel filaments supports the idea that stars are formed in the filaments and become more dispersed with time. Both the supernova-induced and spontaneous star formation scenarios are plausible in the environmental context of CMa-l224. However, our results indicate that a spontaneous gravitational collapse of filaments is a more likely scenario. The methods developed for CMa-l224 can be used for larger regions in the Galactic plane where the same set of photometry is available.

Mapping Spatial Variations of H I Turbulent Properties in the Small and Large Magellanic Cloud

Abstract: We developed methods for mapping spatial variations of the spatial power spectrum (SPS) and structure function (SF) slopes, with a goal of connecting neutral hydrogen (HI) statistical properties with the turbulent drivers. The new methods were applied on the HI observations of the Small and Large Magellanic Clouds (SMC and LMC). In the case of the SMC, we find highly uniform turbulent properties of HI, with no evidence for local enhancements of turbulence due to stellar feedback. Such properties could be caused by a significant turbulent driving on large-scales. Alternatively, a significant line-of-sight depth of the SMC could be masking out localized regions with a steeper SPS slope caused by stellar feedback. In contrast to the SMC, the LMC HI shows a large diversity in terms of its turbulent properties. Across most of the LMC, the small-scale SPS slope is steeper than the large-scale slope due to the presence of the HI disk. On small spatial scales, we find several areas of localized steepening of the SPS slope around major HII regions, with the 30 Doradus region being the most prominent. This is in agreement with predictions from numerical simulations which suggest steepening of the SPS slope due to stellar feedback eroding and destroying interstellar clouds. We also find localized steepening of the large-scale SPS slope in the outskirts of the LMC. This is likely caused by the flaring of the HI disk, or alternatively ram-pressure stripping of the LMC disk due to the interactions with the surrounding halo gas.

Mapping Spatial Variations of HI Turbulent Properties in the Small and Large Magellanic Cloud

Abstract: We developed methods for mapping spatial variations of the spatial power spectrum (SPS) and structure function (SF) slopes, with a goal of connecting neutral hydrogen (HI) statistical properties with the turbulent drivers. The new methods were applied on the HI observations of the Small and Large Magellanic Clouds (SMC and LMC). In the case of the SMC, we find highly uniform turbulent properties of HI, with no evidence for local enhancements of turbulence due to stellar feedback. Such properties could be caused by a significant turbulent driving on large-scales. Alternatively, a significant line-of-sight depth of the SMC could be masking out localized regions with a steeper SPS slope caused by stellar feedback. In contrast to the SMC, the LMC HI shows a large diversity in terms of its turbulent properties. Across most of the LMC, the small-scale SPS slope is steeper than the large-scale slope due to the presence of the HI disk. On small spatial scales, we find several areas of localized steepening of the SPS slope around major HII regions, with the 30 Doradus region being the most prominent. This is in agreement with predictions from numerical simulations which suggest steepening of the SPS slope due to stellar feedback eroding and destroying interstellar clouds. We also find localized steepening of the large-scale SPS slope in the outskirts of the LMC. This is likely caused by the flaring of the HI disk, or alternatively ram-pressure stripping of the LMC disk due to the interactions with the surrounding halo gas.