SELECTED PUBLICATIONS
SELECTED PUBLICATIONS
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Highlights of some of the recent work are shown below. Complete list of publications is available here
Hub-filament systems (HFSs) are potential sites of formation of star clusters and high mass stars. In this work we studied the HFS associated with G326.27-0.49 to provide observational constraints on current theories that attempt to explain star formation globally. The work used infrared data of dust continuum and newly obtained observations on molecular tracers using the APEX (Atacama Pathfinder EXperiment) telescope. The spectroscopic observations were used to identify velocity-coherent structures (filaments and clumps) and study their properties at a resolution of 0.4 pc. We conclude that the region consists of a network of filaments through which mass accretes ( ∼1e-4 Msun/yr) onto the hub. The hub and some of the ends of filaments appear to be undergoing collapse to form new stars. This study identified a target region for future high-resolution studies that would probe the link between the core and filament evolution.
This work investigated the impact of radiative and mechanical feedback from O-type stars on their parent molecular clouds and the triggering of formation of a future generation of stars in the case of the infrared bubble S111 created by the embedded massive stellar cluster G316.80–0.05. We analyzed spectroscopic maps of singly ionized carbon, 13CO, C18O and HCO+ to (i) clearly identify evidence of a shell expanding with a moderate velocity, (ii) show that the The pressure causing the expansion of the H ii region arises mainly from hydrogen ionization and dust-processed radiation. The compressed shells are sites of active star formation as shown by the presence of far-infrared sources with broad outflow activity and based on the age of the HII region we concluded that the expansion of the shell is responsible for triggering the current star formation activity in the region.
We detected significant columns of C+ and O and used a two-layer toy model to explain the self-absorption features seen in both the [CII] and [O I] 63 micron spectra to be arising due to large columns of cold gas in the foreground layers of the PDRs created by S1.
This was the first detection of the 13C isotopes of the carbon chain molecule CCC in the ISM. We found the column density ratio N(13CCC)/N(C13CC) to be different from the statistically predicted value and proposed that the discrepant abundance ratio arises due to the lower zero-point energy of C13CC, which makes position-exchange reaction converting 13CCC to C13CC energetically favorable.
In this work we showed that even though the Treasure Chest is one of the youngest, 1.3 Myr, it is still too old to have been triggered by the formation of the cometary globule. It is far more likely that the Treasure Chest had already formed before G287.84 became a cometary globule, and when the Carina H II region expanded, it blew away the lower density gas, first creating a giant pillar, which later became the cometary globule that we see today. The expanding H II region from the Treasure Chest cluster appears to erode the globule even faster. It is likely that the time scale for star formation is longer than the time it takes for the globule to be evaporated by the FUV radiation from the Treasure Chest cluster, as well as by the FUV radiation from η Car and the O stars in Trumpler 16.
Mookerjea, Sandell et al A&A 2019, 626, A131
In this work using 158 micron [CII] emission we detected CO-dark molecular gas in two regions of the galaxy M33. The observed strong variation in the [C II] emission, not associated with CO and H I could not be explained in terms of differences in visual extinction, far-ultraviolet radiation field, and metallicity between the two studied regions. We concluded that the relative amounts of diffuse (CO-dark) and dense molecular gas possibly vary on spatial scales smaller than 50 pc.
Figure shows [C II] (black), CO(2–1) (green), and H I (blue) spectra at selected positions in the center of M 33. The H I spectrum has been scaled by a factor of 0.005 for easier comparison. The fit to the observed [C II] spectrum, as obtained from the method described in the paper is shown in red and the residual spectrum (vertically offset) is shown in magenta. The residual spectrum corresponds to molecular gas undetected in CO, the CO-dark gas.
Mookerjea, Kramer et al. A&A, 2016, 586, A37
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