arXiv subjects

Tapas Baug

Publications and source records attributed to Tapas Baug.

At least 19 recordsLinked to original sources

arXiv2026

ALMA Reveals an Explosive Outflow Candidate in IRAS 16119--5048

We present a multiwavelength study of the massive star formation region IRAS 16119-5048 (I16119) using ALMA ATOMS Band 3 and QUARKS Band 6 observations, complemented by archival ATCA radio continuum and Spitzer mid-infrared data. The CO (2-1) emission reveals a system of high-velocity streamer-like structures around the central region. Using dendrogram analysis of velocity-channel maps followed by linking in position-position-velocity space, we identify 16 approximately radially distributed streamers whose projected trajectories converge toward a common central region. The kinetic energy of the outflows is at least an order of magnitude lower than those of most known explosive outflows, while their mass entrainment and momentum rates are high compared with typical protostellar outflows, suggesting that I16119 may represent a low-energy explosive outflow candidate. Dense-gas and photodissociation-region tracers reveal shell-like structures associated with the 8 $\mu$m emission, indicating that feedback from the H II region may influence the streamer morphology. The 1.3 mm continuum resolves 27 dense cores along a fragmented filamentary structure. Their separations are consistent with thermal Jeans or cylindrical fragmentation, while the collect-and-collapse scenario is unsupported. The dense cores also show evidence of mass segregation, with the most massive cores concentrated near the inferred explosive centre. We suggest that I16119 is a plausible low-energy explosive outflow candidate, possibly triggered by dynamical interactions among centrally concentrated massive cores. However, the complex velocity structure and possible contamination from individual core-driven outflows prevent a definitive classification. More sensitive, higher angular-resolution observations are required to confirm the nature of the outflow.

astro-ph.GA↗

arXiv2026

Cloud Scale Star Formation and Gas Scaling Relations in the Milky Way

We investigate cloud-scale star formation in the Milky Way using a sample of 45 molecular clouds (sizes of $5-240$ pc) in the inner Galactic plane, spanning heliocentric distances of $1.1-14.4$ kpc. Masses of these clouds are derived from $^{12}$CO and $^{13}$CO emission, while stellar masses are estimated using the young stellar object (YSO) population. The studied molecular clouds have masses ranging from $\sim10^{3}$ to $2.3\times10^{6}$ $\rm M_\odot$, with star formation efficiencies (SFE) up to 0.33. We find a tight, nearly linear scaling of the star formation rate (SFR) with the cloud mass, indicating that more massive clouds form proportionally more stars. The SFE, however, shows a declining trend with cloud mass. The relation between the star formation rate surface density ($\Sigma_{\rm SFR}$) and gas surface density ($\Sigma_{\rm gas}$) exhibits substantial cloud-to-cloud scatter, indicating that the canonical Kennicutt--Schmidt law is not strongly recovered at the scale of individual molecular clouds. Incorporating the cloud free-fall time ($\rm t_{ff}$) into the star formation scaling relation highlights its important role in regulating star formation, although the observed relations suggest that the star formation efficiency per free-fall time is not universal. In particular, the SFE decreases with increasing gas mass available per free-fall time. We discuss the implications of our results in the context of recent theoretical models of molecular cloud evolution and star formation.

astro-ph.GA↗

arXiv2026

Evolution of starless cores in massive clumps seen by the ALMA ASHES and QUARKS surveys

We present a systematic comparative analysis of 324 starless cores in early-phase infrared-dark clouds (IRDCs; ASHES survey) and evolved-phase infrared-bright clouds (IRBCs; QUARKS survey) using 1.3 mm continuum and line data by the Atacama Large Millimeter/submillimeter Array (ALMA). Despite having comparable sizes ($\sim$2500 au),starless cores in IRBCs exhibit systematically higher median mass ($1.5\,M_{\odot}$ vs. $0.6\,M_{\odot}$), number density, and surface density--enhancements of approximately a factor of two relative to starless cores in IRDCs. Starless cores in IRBCs also display relatively stronger non-thermal motions ($\rm\sigma \sim 0.5\,km\,s^{-1}$ vs. $\rm0.3\,km\,s^{-1}$), higher total virial parameters (median $\alpha_{\mathrm{vir,tot}} \sim$ 2.3 vs. 1.0), and steeper density profiles, indicating more centrally concentrated structures in feedback-driven, turbulence-enhanced environments. These findings support a dual evolutionary origin: (i) new core formation in evolved IRBCs under altered initial conditions, and (ii) subsequent dynamical mass growth via accretion from extended reservoirs. The prevalence of low-mass starless cores--even in late-stage IRBC environments--challenges models requiring massive prestellar cores and instead favors competitive-like dynamical mass accretion scenarios for high-mass star formation.

astro-ph.GA↗

arXiv2026

Digging into the Massive Protostar S255IR NIRS3: A Study of Nitrogen-Bearing Molecules and Their Prebiotic Chemistry

The study of complex nitrogen (N)-bearing molecules is essential for probing the physical and chemical evolution of star-forming regions. In this paper, we present the identification of rotational emission lines from several complex N-bearing species such as methyl cyanide (CH$_{3}$CN), ethyl cyanide (C$_{2}$H$_{5}$CN), vinyl cyanide (C$_{2}$H$_{3}$CN), cyanamide (NH$_{2}$CN), and formamide (NH$_{2}$CHO) toward the high-mass protostar S255IR NIRS3 using ALMA band 4 observations. In addition, the vibrationally excited transitions of cyanoacetylene (HC$_{3}$N, $\nu_{7}$ = 2) were detected. The column densities and excitation temperatures of these molecules were derived through LTE spectral modelling, yielding excitation temperatures in the range of 175$-$220 K. The high excitation temperatures (175$-$220 K) indicate that the identified N-bearing molecules arise from the warm inner regions ($T \geq 100$ K) of the source. The fractional abundances were further estimated relative to H$_{2}$, CH$_{3}$OH, and CH$_{3}$CN. A Pearson correlation heat map of the abundances reveals a strong positive correlation ($r > 0.7$) among three molecules in the cyanide family, such as CH$_{3}$CN, C$_{2}$H$_{3}$CN, and C$_{2}$H$_{5}$CN, suggesting that these N-bearing molecules may be chemically linked. Comparison with three-phase warm-up chemical models shows that the observed abundances of CH$_{3}$CN, C$_{2}$H$_{5}$CN, C$_{2}$H$_{3}$CN, NH$_{2}$CN, NH$_{2}$CHO, and HC$_{3}$N ($\nu_{7}$ = 2) relative to H$_{2}$ are consistent with model predictions within factors of 1.04, 0.67, 1.28, 0.76, 0.72, and 0.96, respectively. Finally, we discuss the potential formation pathways of the identified N-bearing molecules in the context of gas-grain chemistry within S255IR NIRS3.

astro-ph.GA↗

arXiv2026

Discovery of a Compact Hub-Filament System in G286.21+0.17 with JWST and ALMA: Insights into Protocluster Formation and Competitive Accretion

We present a multi-wavelength study of the massive protocluster G286.21+0.17 (G286) using \emph{JWST} near-infrared imaging and ALMA H$^{13}$CO$^{+}$(1--0) observations. The \emph{JWST} images uncover a compact ($\sim$0.5 pc) hub-filament system (HFS), comprising a dense central hub connected by at least four converging filaments seen in absorption, along with multiple H$_2$ protostellar jets/outflows. The hub hosts dense core G286c1. The H$^{13}$CO$^{+}$ emission confirms this HFS over [$-$19.2, $-$16.4]~km~s$^{-1}$. The \emph{JWST} images further trace prominent photodissociation regions around the H\,{\sc ii}~region~A, powered by a B-type star. The radial distribution of ALMAGAL 1.38 mm core properties reveals steep power-law slopes toward the hub center. Within the inner hub (r < 8'', $\sim0.1$~pc), the core number density follows $\rho~[\rm pc^{-2}] \propto r^{-2.4\pm0.5}$, the surface density scales as $\Sigma~[\rm g~cm^{-2}] \propto r^{-1.0\pm0.2}$, and the enclosed core mass varies as $M_{\rm core}~[M_{\odot}] \propto r^{-1.2\pm0.2}$, while core diameters remain approximately constant ($D_{\rm core}~[\rm AU] \propto r^{-0.1\pm0.1}$). These trends, along with filament mass accretion rates of $7\times10^{-6}$--$1.8\times10^{-4}$~$M_\odot$~yr$^{-1}$, support a competitive accretion scenario in which gravitational focusing enhances core growth toward the hub center. Filament linewidths increase from tail/outer-region to head/hub-region, consistent with gravity-driven turbulence. However, the absence of a preferred alignment between velocity gradients and gravitational force directions may indicate a dynamically evolved system. The HFS likely formed through large-scale gas layer interactions and compression by the adjacent H\,{\sc ii} region. Overall, star formation in G286 appears regulated by filamentary accretion, competitive core growth in the hub, and stellar feedback.

astro-ph.GA↗

arXiv2026

ALMA-QUARKS view of W49N: Multipolar episodic outflow associated with the most energetic Galactic water maser

We present a detailed investigation of a multipolar episodic molecular outflow in the mini-starburst region W49N, which hosts the most luminous water maser in the Galaxy. Using high-resolution ($\sim$0.3 arcsec) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the $\mathrm{^{12}CO}$ emission as part of the ALMA-QUARKS survey, we analyze the morphology and kinematics of the outflow. Our observations reveal four newly identified outflow lobes in addition to the previously known central bipolar jet. These lobes appear more jet-like rather than exhibiting wide opening angles. Based on the $\mathrm{^{12}CO}$ (2-1) and $\mathrm{^{13}CO}$ (2-1) emission, we provide a more reliable estimate of the outflow's physical parameters, confirming it as one of the most energetic outflows in the Galaxy. Notably, these newly discovered lobes exhibit chains of knots, a characteristic signature of episodic ejection. Furthermore, two of the lobes display prominent S-shaped wiggles, suggestive of a precessing jet. The discovery of these features -- commonly observed in outflows from low-mass protostars -- in such an extreme massive star-forming environment provides compelling evidence that some underlying physical mechanisms for launching outflows are conserved across a wide range of stellar masses.

astro-ph.GA↗

arXiv2026

The ALMA-QUARKS Survey: Evidence of an Explosive Molecular Outflow in IRAS 15520--5234

We present a study of the massive protocluster IRAS 15520$-$5234, which displays evidence of an explosive molecular outflow that unleashed a kinetic energy of at least 10$^{48}$ erg. The protocluster contains 16 dense cores detected in the ALMA band 6 continuum emission maps, having masses in the range from 0.2 to 11.0 M$_{\odot}$. Our analysis of CO $(2-1)$ emission reveals 28 well collimated outflow fingers, the majority of which follow a Hubble-Lema\^itre velocity law. The outflow fingers show no preferred orientation in the plane of sky and emerge from a common center of origin. We estimate the total mass, momentum, and kinetic energy of the outflow fingers and find that the values are at least one order of magnitude higher than the typical bipolar outflows associated with massive protostars. The morphology and kinematics of the outflow fingers suggest that the outflow associated with IRAS 15520$-$5234 is explosive in nature. We calculate the dynamical age of the explosive event to be approximately 6550 years. Additionally, we estimate the frequency of such explosive outflows in the Galaxy, which is one event every 83 years. Finally, we speculate that the rearrangement of masses within the massive protocluster and the dynamical interaction among the massive cores may result in the formation of such an energetic event.

astro-ph.GA↗

arXiv2026

The ALMA-QUARKS Survey: Discovery of Dusty Fibrils inside Massive Star-forming Clumps

We report the discovery of more than 323 superfine dusty filamentary structures (fibrils) inside 121 massive star forming clumps that are located in widely different Galactic environments (Galactocentric distances of $\sim$0.5-12.7 kpc). These fibrils are identified from the 1.3~mm continuum emission in the ALMA-QUARKS survey, which has a linear resolution of $\sim900$ AU for a source at $\sim$3 kpc, using the \textit{FilFinder} software. Using \textit{RadFil} software, we find that the typical width of these fibrils is $\sim$0.01 pc, which is about ten times narrower than that of dusty filaments in nearby clouds identified by the \textit{Herschel} Space Observatory. The mass ($M$) versus length ($L$) relation for these fibrils follows $M\propto L^{2}$, similar to that of Galactic filaments identified in space (e.g., \textit{Herschel}) and ground-based single-dish (e.g., \textit{APEX}) surveys. However, these fibrils are significantly denser ($\mathrm{N_{H_2} = 10^{23}-10^{24}\ cm^{-2}}$) than the filaments found in previous \textit{Herschel} surveys ($\mathrm{N_{H_2} = 10^{20}-10^{23}\ cm^{-2}}$). This work contributes a large sample of superfine fibrils in massive clumps, following the identification of large 0.1-pc wide filaments and associated internal velocity coherent fibers in nearby molecular clouds, further emphasizing the crucial role played by filamentary structures in star formation at various physical scales.

astro-ph.GA↗

arXiv2026

ATOMS-QUARKS survey: Inflow and infall in massive protocluster G318.049+00.086: Evidence of competitive accretion

We present a gas kinematic study of the massive protocluster G318.049+00.086. The protocluster is reported to contain 12 prestellar core candidates and 4 protostellar cores. Filamentary structures are identified using the 1.3 mm dust continuum map, with four of them converge into a dense central region, forming a hub-filament system (HFS). High velocity gradients (10 - 20 km s$^{-1}$ pc$^{-1}$) derived from PV analysis of H$^{13}$CO$^{+}$ emission along three of those filaments are suggestive of mass inflow onto the central hub. A mass inflow rate higher than $10^{3}$ M$_{\odot}$ Myr$^{-1}$ along the filaments is indicating that the central hub is capable of forming massive star(s). Investigation of H$^{13}$CO$^{+}$ and CCH spectral profiles revealed the majority of the cores having the characteristic blue asymmetric line profiles, typical signature of gravitational collapse. The remaining few cores showed red asymmetric profiles, indicative of gas expansion. Also, the derived mass infall rates for the protostellar cores in hub-region is significantly higher in comparison to those located along the filaments. The mass-radius relationship of the cores revealed that the cores with red profiles reside in the massive star formation regime. However, the global velocity gradient along the filaments suggests that these particular cores are losing material to the hub. Our results are supporting a competitive accretion scenario of massive star formation where gas is expected to be funnelled from less gravitationally dominant cores to the cores located at the gravitationally favorable position.

astro-ph.GA↗

arXiv2026

The Structure of an 80 pc Long Massive Filament

Using new Institut de Radioastronomie Millim\'etrique (IRAM) 30m telescope $\rm N_2H^+$, $\rm C^{18}O$ $J$=1-0 and Atacama Pathfinder Experiment (APEX) telescope $\rm ^{13}CO$ and $\rm C^{18}O$ $J$=2-1 maps together with archival far-infrared continuum data, and $\rm ^{12}CO$, and $\rm ^{13}CO$ $J$=1-0 data, we present a comprehensive analysis of the massive filament CFG024.00$+$0.48 (G24) across clump-to-cloud scales. Our results show that G24 is an $\sim$80 pc giant filament with a total mass of $\sim$$10^5$ M$_{\odot}$. In the different tracers the filament width is measured to be about $\sim$2 times the beam size of the observations, as expected for power-law density distributions, giving beam-deconvolved widths in the range from 0.8 to 2.8 pc. We determine a line-of-sight thickness of $\sim$2.2 pc demonstrating that G24 is not an edge-on, flatten structure. The virial parameter obtained from line mass ($\alpha_{\rm line,vir}=M_{\rm line,vir}/M_{\rm line}$) from the $\rm C^{18}O$ (1-0) data is 0.85, and that obtained from $Herschel$-based H$_2$ column density is 0.52, suggesting G24 is globally close to virial equilibrium. The distribution of the 40 dust clumps appears to have a ''two-tier'' fragmentation pattern. For the clump groups, the separation, with a mean/median of 3.68/3.46 pc, is very close to expected length associated with the maximum fragmentation growth rate of $\lambda_{\rm max}=3.55 \pm0.32$ pc estimated for the dust. However, the longitudinal centroid velocity profiles of $\rm C^{18}O$ and $\rm N_2H^+$ show oscillation patterns with wavelengths of 9.8$\pm$0.1 pc and 9.9$\pm$0.1 pc, respectively. This is $\sim$2 times larger than the corresponding values of $\lambda_{\rm max}$ of 4.96$\pm$0.63 pc and 4.65$\pm$1.34 pc, respectively. This suggests that the velocity structure is not dominated by flows directly associated with the fragmentation seen in the dust emission.

astro-ph.GA↗

arXiv2025

Unveiling the Dual Nature of V1180 Cas: UXor-like Dips and EXor-like Bursts Across a Decade

We present a detailed analysis of the long-term photometric and spectroscopic evolution of V1180 Cas over a decade, aiming to identify the dominant mechanisms behind its variability. We combine multi-band light curves from 1999 to 2025 with over 30 epochs of optical to near-infrared spectroscopy (0.5-2.5 $\mu$m), analyzing variability patterns, color behavior, and emission line diagnostics. We investigate the temporal evolution of accretion and outflow indicators and their correlation with photometric states. The light curve reveals a transition from sporadic early dimming events to a quasi-periodic pattern since 2018, with eleven major dips showing asymmetry and stochastic sub-structure. Color-magnitude diagrams show classic UXor-like blueing during deep minima, while near-infrared and mid-infrared color changes indicate thermal evolution of disk. Spectroscopic analysis reveals persistent hydrogen, Ca II, He I, and forbidden line emission. Accretion diagnostics track photometric variability, and forbidden lines often intensify during dips, implying a physical link between extinction and outflows. Estimated accretion rates range from $\sim10^{-8}-10^{-7}$ $M_\odot$yr$^{-1}$; the outflow rate and density diagnostics are consistent with disk winds and shock-excited jets. V1180 Cas demonstrates dual-mode variability driven by both variable circumstellar extinction and episodic accretion events. The hybrid UXor/EXor behavior, combined with evolving disk signatures and persistent outflows, suggests a young stellar object undergoing coupled accretion-extinction-outflow evolution. Continued monitoring will be essential to fully resolve the physical processes shaping its variability.

astro-ph.SR↗

arXiv2025

The ALMA-QUARKS survey: Evidence of a candidate high-mass prestellar core aside a bright-rimmed cloud IRAS 18290-0924

Although frequently reported in observations, the definitive confirmation of high-mass prestellar cores has remained elusive, presenting a persistent challenge in star formation studies. Using two-band observational data from the 3mm ATOMS and 1.3mm QUARKS surveys, we report a high-mass prestellar core candidate, C2, located on the side of the bright-rimmed cloud IRAS 18290-0924. The C2 core identified from the 3mm continuum data of the ATOMS survey ($\sim$2 arcsecond, $\rm\sim 10000~au$ at 5.3 kpc) has a mass ranging from 27-68 $M_{\odot}$ for temperatures 10-22K within a radius of $\sim$2800 au. The highest-resolution ($\sim$0.3 arcsecond, $\rm\sim 1500 au$) observations of this source presented to date from the QUARKS survey reveal no evidence of further fragmentation. Further analysis of a total $\sim$10 GHz band width of molecular line survey does not find star-formation activity (e.g., outflows, ionized gas) associated with the core, with a few molecular lines of cold gas detected only. Additionally, virial analysis indicates the C2 core is gravitationally bound ($\alpha_{\rm vir} \sim0.1-0.3$) and thus could be undergoing collapse toward star formation. These results strongly establish a candidate for a high-mass prestellar core, contributing to the very limited number of such sources known to date.

astro-ph.GA↗

arXiv2025

The ALMA-ATOMS-QUARKS survey: Resolving a chemically rich massive protostellar outflow

We present a comprehensive study on the physical and chemical structures of a chemically rich bipolar outflow in a high-mass star forming region IRAS 16272$-$4837 (SDC335), utilizing high-resolution spectral line data at 1.3 mm and 3 mm dual-bands from the ALMA ATOMS and QUARKS surveys. The high-velocity jet is enveloped by a lower-velocity outflow cavity, containing bright knots that show enhanced molecular intensities and elevated excitation temperatures. Along the outflow, we have identified 35 transitions from 22 molecular species. By analyzing the spatial distribution and kinematics of these molecular lines, we find that the molecular inventory in the outflow is regulated by three processes: (i) direct entrainment from the natal molecular core by the outflow; (ii) shock-induced release of molecules or atoms from dust grains; and (iii) thermal desorption and gas-phase reactions driven by shock heating. These results confirm that outflows are not only dynamical structures but also active chemical factories, where entrainment, shocks, and thermal processing jointly enrich the molecular content. Our findings confirmed that outflow chemistry has multi-origin nature, and provide critical insights into chemical evolution during high-mass star formation.

astro-ph.GA↗

arXiv2025

The ALMA-QUARKS Survey: III. Clump-to-core fragmentation and search for high-mass starless cores

The Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures (QUARKS) survey observed 139 infrared-bright (IR-bright) massive protoclusters at 1.3 mm wavelength with ALMA. This study investigates clump-to-core fragmentation and searches for candidate high-mass starless cores within IR-bright clumps using combined ALMA 12-m (C-2) and Atacama Compact Array (ACA) 7-m data, providing $\sim$ 1 arcsec ($\sim\rm0.02~pc$ at 3.7 kpc) resolution and $\sim\rm0.6\,mJy\,beam^{-1}$ continuum sensitivity ($\sim 0.3~M_{\odot}$ at 30 K). We identified 1562 compact cores from 1.3 mm continuum emission using getsf. Observed linear core separations ($\lambda_{\rm obs}$) are significantly less than the thermal Jeans length ($\lambda_{\rm J}$), with the $\lambda_{\rm obs}/\lambda_{\rm J}$ ratios peaking at $\sim0.2$. This indicates that thermal Jeans fragmentation has taken place within the IR-bright protocluster clumps studied here. The observed low ratio of $\lambda_{\rm obs}/\lambda_{\rm J}\ll 1$ could be the result of evolving core separation or hierarchical fragmentation. Based on associated signatures of star formation (e.g., outflows and ionized gas), we classified cores into three categories: 127 starless, 971 warm, and 464 evolved cores. Two starless cores have mass exceeding 16$\,M_{\odot}$, and represent high-mass candidates. The scarcity of such candidates suggests that competitive accretion-type models could be more applicable than turbulent core accretion-type models in high-mass star formation within these IR-bright protocluster clumps.

astro-ph.GA↗

arXiv2025

The ALMA-ATOMS Survey: Exploring Protostellar Outflows in HC$_3$N

We present the first systematic study of bipolar outflows using HC$_3$N as a tracer in a sample of 146 massive star-forming regions from ALMA-ATOMS survey. Protostellar outflows arise at the initial stage of star formation as a consequence of active accretion. In general, these outflows play a pivotal role in regulating the star formation processes by injecting energetic material in the parent molecular clouds. In such process, lower velocity components of outflows contain a significant portion of the energy. However, extraction of those component is difficult as the corresponding gas is often mixed with that of the ambient cloud. In our sample, we identified 44 bipolar outflows and one explosive outflow in HC$_3$N (J=11--10). The host clumps of these outflows are found to be at different evolutionary stages, suggesting that outflows in HC$_3$N are detectable in different stages of star formation. Also, the non-correlation of HC$_3$N outflows with clump evolutionary stages suggests that HC$_3$N is an unbiased tracer of outflows. Analyses revealed that HC$_3$N performs slightly better in detecting low-velocity components of outflows than traditionally employed tracers like SiO. The derived outflow parameters (i.e outflow mass, momentum, and energy) show moderate correlations with clump mass and luminosity. Our analysis of outflow opening angles and position-velocity diagrams across the outflow lobes show that, HC$_3$N is not only a good tracer of low-velocity outflows, but can also detect high-velocity collimated outflows. Overall, this study indicates that HC$_3$N can be used as a complementary outflow tracer along with the traditionally known outflow tracers, particularly in the detection of the low-velocity components of outflows.

astro-ph.GA↗

arXiv2025

Research on the Interstellar Medium and Star Formation in the Galaxy: An Indian Perspective

Although the star formation process has been studied for decades, many important aspects of the physics involved remain unsolved. Recent advancement of instrumentation in the infrared, far-infrared and sub-millimetre wavelength regimes have contributed to a significantly improved understanding of processes in the interstellar medium (ISM) leading to star formation. The future of research on the ISM and star formation looks exciting with instruments like the JWST, ALMA, etc., already contributing to the topic by gathering high-resolution high-sensitivity data and with several larger ground- and space-bound facilities either being planned or constructed. India has a sizable number of astronomers engaged in research on topics related to the ISM and star formation. In this white paper invited by the Astronomical Society of India to prepare a vision document for Indian astronomy, we review the Indian contributions to the global understanding of the star formation process and suggest areas that require focused efforts both in creating observing facilities and in theoretical front in India, in order to improve the impact of our research in the coming decades.

astro-ph.GA↗

arXiv2024

JWST-ALMA Study of a Hub-Filament System in the Nascent Phase

Star clusters, including high-mass stars, form within hub-filament systems (HFSs). Observations of HFSs that remain unaffected by feedback from embedded stars are rare yet crucial for understanding the mass inflow process in high-mass star formation. Using the JWST NIRCAM images, Dewangan et al. 2024, reported that the high-mass protostar G11P1 is embedded in a candidate HFS (G11P1-HFS; $<0.6$ pc). Utilizing ALMA N$_{2}$H$^{+}$(1-0) data, we confirm the presence of G11P1-HFS and study the dense gas kinematics. We analyzed the position-position-velocity (PPV) map and estimated on-sky velocity gradient ($V_g$) and gravity ($\mathcal{F}_{g}$) vectors. The spatial distribution of gas velocity and H$_2$ column density was examined. The steep $V_g$ of 5 km s$^{-1}$ pc$^{-1}$ and $-$7 km s$^{-1}$ pc$^{-1}$ toward either side of G11P1-hub, and the decreasing $V_g$ toward the hub, identify G11P1-HFS as a small-scale HFS in its nascent phase. $V_g$ and $\mathcal{F}_{g}$ align along the filaments, indicating gravity-driven flows. This work highlights the wiggled, funnel-shaped morphology of a HFS in PPV space, suggesting the importance of subfilaments or transverse gas flows in mass transportation to the hub.

astro-ph.GA↗

arXiv2024

Radio Continuum Halos of 7 Nearby Large Galaxies using uGMRT

We present the results of deep radio observations of 7 nearby large galaxies observed using the upgraded Giant Metrewave Radio Telescope (uGMRT) 0.3-0.5 GHz receivers with an angular resolution of $\sim$10 arcsec. The achieved sensitivities of these observations range from $\approx$15 to 50 $\mu$Jy/beam which is $\approx$3-4 factor lower than the previous observations at these frequencies. For 2 galaxies (NGC3344 and NGC3627) with moderate inclination angles, significant diffuse emissions are seen for the first time. Detected radio halos in the vertical direction are significantly larger in our 0.4 GHz maps than compared to the observations at $\sim$1.5 GHz for 4 nearly edge-on galaxies - NGC3623, NGC4096, NGC4594, and NGC4631. For these 4 galaxies, significantly larger halos are also detected along the galaxy disk. For NGC3623 and NGC4594, we could detect elongated radio disks which was not seen before. We also present new uGMRT images of NGC3344 and NGC3623 at 1.3 GHz and a new VLA image of NGC3627 at 1.5 GHz. We fitted an exponential function to the flux densities along different cross-cuts and found a significantly wider distribution at 0.4 GHz uGMRT images than compared to the high-frequency images at $\sim$1.5 GHz. Using maps at 0.144, 0.4, and $\sim$1.5 GHz, we made spectral index maps of the 7 sample galaxies and found steepening of the spectrum up to a value of $\sim$ -1.5 in the halo regions of the galaxies.

astro-ph.GA↗