Manash Samal

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Some research highlights/key-results of my work from 2018 and onwords

In a recent work, we unveil an extremely young of age ∼0.5 Myr, located in the hub of the cloud G148.24+00.41 with TANSPEC near-infrared cemara. We find that the cluser is currently forming stars at an efficiency of 20% and a rate of 330 Msun/Myr, and has potential to became a massive cluster of mass greater than 1000 Msun. Such young clusters are extremely important for understanding the early evolution and growth of star clusters. For details see Rawat et al.2024,AJ,168,136 Posted Septmber 10th, 2024

The presence of extended Main-Sequence Turn-Off (eMSTO) in the open clusters has been attributed to various factors, such as spread in rotation rates, binary stars, and dust-like extinction from stellar excretion discs. In a recent work, we present a comprehensive analysis of the open cluster NGC 2355 and find that the origin of eMSTO in NGC 2355 is possibly caused by the spread in rotation rates of stars. We also discuss the star-disc interaction mechanism as that the likley origin of spread in rotation rates in this cluster. For details see Maurya et al. 2024. Posted June 10th, 2024

We report discovery of a new hot post-asymptotic giant branch (PAGB) star in the Galactic globular cluster (GC) E3. The star stands out as the brightest source in E3 in the Astrosat/UVIT images. Our analyses suggest that the star is in a likley binary systems with a binary period of either 39.12 days or 17.83 days, and is enriched with C and O abundances. This is one of the first of the identified PAGB stars in a GC to show binary signature, thus, identifications such systems are important for understanding the evolution of PAGB stars through binary interaction. For details see Kumar et al. 2024. Posted May 20th, 2024

Jets and outflows are signposts of stellar birth. They allow stars to lose angular momentum, thus, preventing stars from spinning out of control while they grow. In this work, using the near-infrared observation at 2.12 μm, 127 outflows were identified in two molecular cloud complexes of our Galaxy. Seventy-nine percent of the outflow driving sources were identified as Class 0/I protostars with a typical ejection frequency of ~1.2 kyr. Radiative transfer modelling suggests that the majority of the jets were driven by intermediate-mass protostars. The identified jet-bearing protostellar sample will pave the way to understand many aspects of outflows with future high-resolution observations. Posted April 10th, 2024

In a recent work, using high-resolution dust polarization observations at 850 micron, we explore the relative importance of magnetic field, turbulence, and gravity in the early phases of star formation. We investigated the cluster forming hub of the molecular cloud G148.24+00.41. We find that that in the hub, gravitational energy has an overall edge over magnetic and kinetic energies, thus, would facilitate the growth of star cluster observed in the hub. For details, see Rawat et al. 2024, MNRAS,528,1460 Posted January 07th, 2024

In a recent work, using observations of CO (1-0) isotopologues, we find that cluster formation in the molecular cloud G148.24+00.41 is occuring at the nexus of filamentray flows. We discussed and showed that large-scale filamentary accretion flows towards the central region of the collapsing cloud is an important mechanism for supplying the matter necessary to form massive clumps and subsequent stellar clusters. For details, see Rawat et al. 2024, MNRAS, 528, 2199. Posted January 07th, 2024

Clouds more massive than about 10^5 Msun are potential sites of massive (10^4 Msun) cluster formation. In a recent work, using various observational metrics, we discuss the cluster formation mechanisms and cluster forming potential of the Giant Molecular Cloud (GMC) G148.24+00.41. Comparing our results with the models of star cluster formation, we conclude that the GMC has the potential to form a star cluster in the mass range ∼ 2000–3000 Msun through dynamical hierarchical collapse and assembly of both gas and stars. For details, see Rawat et al. 2023. Posted March 09th, 2024

In a recent work, using Gaia-DR3 data and machine learning tools, we identified members of Tr-37 young cluster over 7.1 degree^2 area. Doing kinematic analysis, we find that cluster members are expanding at a rate of 1.1 km/s, which is found to be slower compared to the expansion velocity, ~5 km/s, of the molecular gas in the complex. We discussed that this slow expansion of the cluster is likley due to the fact that most of the cluster members are still bound and the cluster is still not significantly dynamically evolved. For details, see Das et al. 2023. Posted March 3rd, 2023

The first hydrostatic core (FHSC) is the first object to form at the centre of a collapsing prestellar core. Until now, molecular jets have been observed in early Class0 protostars. Using ALMA observation, for the first time, we detect a dense molecular jet in SiO emission from a source that has the characteristics of FHSCs as predicated by theory. We conclude that the source may be the earliest object discovered in the protostellar phase with a molecular jet. For details see Dutta et al. 2022. Posted May 11, 2022

In a recent work, using UKDISS, GMRT, and Herschel observations, we find evidences that the formation of a young cluster (and HII region) has occurred at the very end of a long filamentary cloud around 3 Myr ago, likely due to longitudinal collapse of the filament and second generation star formation is currently occuring in a clump at the junction of the HII region and filament. We propose that the star formation in the clump is either induced or being facilitated by the compression of the expanding HII region onto the inflowing filamentary material. For details see Yadav et al. 2021. Posted November 17th, 2021

In a recent work, we perform the deepest and widest optical photometry of Cygnus OB2 complex using Subaru 8.0-meter telescope. We detect sources down to ~28 mag and 27 mag in r2 and i2 bands,respectively, which allow us detect young sources down to 0.03 Msun @ 2kpc. For central cluster of the complex, we obtained an age ~5 Myr and a disk fraction ~9%. The disk fraction is on the lower side compared to young clusters of similar age. We propose that this could be due to the external photoevaporation of circumstellar disks by the UV photons of the massive OB stars. For deatails see Gupta et al. 2021. Posted September 24th, 2021

The shape of the mass distribution during the birth of stars and its potential dependence on the environment are not well known. In a recent work, we did analysis of nine young clusters that are under diverse environmental condition. We find that the log-normal fit can well explain the shape of the intial mass function (IMF) and also find no strong evidence of environment on the shape and the characteristic mass of these clusters. For details see Damian et al. 2021 Posted January 27th, 2021

Star formation is an inefficient process and various laws have been formulated to understand what controls star formation.  In a recent article, we tested whether the Kennicutt-Schmidt relation can still be applicable to smaller scales or it is the local conditions that prevail and define the star-formation scaling laws. For details see Das et al. 2020. Posted Septmber 16th, 2020

We released CHIMPS2 survey's 12CO emission data of the Galactic Centre, obtained with the James Clerk Maxwell Telescope (JCMT) at an angular resolution of 15 arcsec and a velocity resolution of 1 km/s. We discuss several applications of these data. For details see Eden et al. 2020. Posted Septmber 16th, 2020

We published a paper on structure and kinematics of PDRs around the compact HII regions S235 A and S235 C using SOFIA, where we discuss the expanding motion of the PDRs into the front molecular layer in both regions. Comparing the various observed line profiles with the spherical expanding models, we suggest that the [OI] line could be a reliable tracer of gas kinematics in PDRs. For details see Kirsanova et al. 2020. Posted July 30th, 2020

We published a paper investigating the orientation, strength, and role of magnetic fields on the two clumps located at the waist of the bipolar H II region Sh2-201, based on JCMT SCUBA-2/POL-2 observations of 850 μm polarized dust emission. From virial analyses and critical mass ratio estimates, we discuss the stability of the clumps. We also discuss the role of the H II region on B-field morphologies around the clumps and the role of B-field in making bipolar HII region. For details see Eswaraiah et al. 2020. Posted December 21st, 2019

In a recent work, we use SOFIA upGREAT observations of [C II] emission toward the H II region complex Sh2-235 to  understand the origin of [C II] emission. We found velocity-integrated [C II] intensity is strongly correlated with  WISE 12 μm intensity across the entire complex, indicating that both trace UV radiation fields. Alos found that the 22 μm and radio continuum intensities  are only correlated with [C II] intensity in the ionized hydrogen portion and the correlations between the [C II] and   molecular gas tracers are poor across the region. For details see Anderson et al. 2019. Posted Septmber 10th, 2019

We present the first release of the data and compact-source catalogue for the JCMT Large Program SCUBA-2 Continuum Observations of Pre-protostellar Evolution (SCOPE). SCOPE consists of 850-um continuum observations of 1235 Planck Galactic Cold Clumps (PGCCs) made with the Submillimetre Common-User Bolometer Array 2 on the James Clerk Maxwell Telescope. These cores will be used to estimate various properties of clouds. For details see Eden et al. 2019. Posted Feb 26th, 2019

We published a paper, where we tried to understand the origin of young, distributed, low-mass stars in cloud complexes. Using GLIMPSE, MIPS, and WISE survey images and point source catalogues, we proposed that star formation induced in the feedback generated structures such as elephant trunk-like structures (ETLSs) is one of the viable mechanisms for forming such stars. For details see Panwar et al. 2019 Posted Jan 3rd, 2019

Based on optical polarization measurements, we published a paper discussing the magnetic field's structure, strength and its role on star formation of a dark globule. We estimated B-field strength to be ∼56 micro gauss, the ratio of magnetic to turbulent pressure to be ∼3, and the ratio of mass to magnetic flux  to be less than 1, implying dominant role of B-fields in comparison to turbulence and gravity in rendering the cloud support. Posted Dec 25th, 2018

We published a paper analyzing a Planck cold clump and filaments associated to it using JCMT, CFHT, and Spitzer Observations, and found that the clump is in the final assemble stage a moderately massive (∼ 240 Msun) cluster. Based our analysis, we attributed its formation is most likely due to the longitudinal collapse of the most massive filament of the complex. Posted Agust 15th, 2018

We published catalog of classical bipolar HII regions of our Galaxy, and based on their morphologies, parental cloud structures, and star formation in their vicinities,  we  proposed that such regions formed in 2D or sheet-like clouds and also proposed a new view of induced star formation in such environments. Posted Agust 3rd, 2018

We published a paper discovering 48 outflows from YSOs in one the massive star forming complex of our Galaxy using UWISH2 near-infrared survey observations. We found that 90% of the outflows are driven by intermediate-mass Class 0/I protostars thatare accreting from their protoplanetary disc. Posted May 30th, 2018

We published a paper carrying investigation on 64 Plank cold clumps using CO lines and 850 micron dust continnum observations, and showed that in these clumps the core formation efficiency is around 3% and the mass-size relation of the core follows a power-law with exponent 1.67 Posted May 10th, 2018

We published a paper on the physical conditions and kinematics  of a filamentary cloud by analyzing CO, NH3, and CS line observations taken with ONSALA and IRAM observatories. In this work, we found that the filament is fragmented into several clumps, which we discuss in the context of observed the  gas dynamical coherence  and evidence of longitudinal collapse of the filament. Posted Feb 20th, 2018

We published a paper analyzing JCMT, SMT, KVN, and NRO data of dust continnum and molecular line observations of a filamentary infrared dark cloud G26. From our analysis, we argued that fragmentation in the G26 filament from cloud scale to clump scale is in agreement with gravitational fragmentation of an isothermal, nonmagnetized, and turbulent supported cylinder.The G26 filament may be formed owing to large-scale compression flows evidenced by the temperature and velocity gradients across its natal cloud. Posted Jan 10th, 2018

We published a paper on dust properties of Planck cold clumps using Herschel and JCMT observations, and showed that the most appropriate value of dust opacity spectral index for such clumps is ~1.7 Posted on Jan 2nd, 2018

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