A5078996274- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Molecular Spectroscopy and Structure
- Astro and Planetary Science
- Orbital Angular Momentum in Optics
- Near-Field Optical Microscopy
- Galaxies: Formation, Evolution, Phenomena
- Atmospheric Ozone and Climate
- Astronomy and Astrophysical Research
- Digital Holography and Microscopy
- Spectroscopy and Laser Applications
- Advanced Combustion Engine Technologies
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Optical Coatings and Gratings
- Marine Biology and Ecology Research
- Sperm and Testicular Function
- Microfluidic and Bio-sensing Technologies
- Scientific Research and Discoveries
- High-pressure geophysics and materials
- Atomic and Molecular Physics
- Astrophysics and Cosmic Phenomena
- Superconducting Materials and Applications
- Plasmonic and Surface Plasmon Research
Massachusetts Institute of Technology
2023-2025
Boston University
2018-2024
Max Planck Institute for Radio Astronomy
2007-2022
Max Planck Society
2005-2019
Max Planck Institute for Astronomy
2019
California Institute of Technology
2010-2016
UNSW Sydney
2015
Tirunelveli Medical College
2011-2014
Center for Astrophysics Harvard & Smithsonian
2007-2014
Anna University, Chennai
2011-2014
The APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) is an unbiased 870 μm submillimetre survey inner Galactic plane (|ℓ| < 60° with |b| 1|$_{.}^{\circ}$|5). It largest and most sensitive ground-based wavelength to date has provided a large systematic inventory all massive, dense clumps in (≥1000 M⊙ at heliocentric distance 20 kpc) includes representative samples earliest embedded stages high-mass star formation. Here, we present first detailed census properties (velocities,...
Whether or not molecular clouds and embedded cloud fragments are stable against collapse is of utmost importance for the study star formation process. Only "supercritical" able to form stars. The virial parameter α = Mvir/M, which compares mass actual mass, provides one way gauge stability collapse. Supercritical characterized by ≲ 2, as indicated a comprehensive analysis considering perturbations in pressure density gradients. Past research has suggested that parameters ≳ 2 prevail clouds....
We present λ1.3 mm CARMA observations of dust polarization toward 30 star-forming cores and 8 regions from the TADPOL survey. show maps all sources, compare ~2.5" resolution with ~20" single-dish submillimeter telescopes. Here we do not attempt to interpret detailed B-field morphology each object. Rather, use average orientations derive conclusions in a statistical sense ensemble bearing mind that these can be quite uncertain. discuss three main findings: (1) A subset sources have consistent...
We present Submillimeter Array (SMA) λ = 0.88 and 1.3 mm broad-band observations, Very Large (VLA) observations in NH3 (J, K) (1,1) up to (5,5), H2O CH3OH maser lines towards the two most massive molecular clumps infrared dark cloud (IRDC) G11.11−0.12. Sensitive high-resolution images reveal hierarchical fragmentation dense gas from ∼1 pc clump scale down ∼0.01 condensation scale. At each scale, mass of fragments is orders magnitude larger than Jeans mass. This common all four IRDC we...
Using spectral-line observations of HNCO, N2H+, and HNC, we investigate the kinematics dense gas in central ~250 pc Galaxy. We present SCOUSE (Semi-automated multi-COmponent Universal Spectral-line fitting Engine), a line algorithm designed to analyse large volumes data efficiently systematically. Unlike techniques which do not account for complex profiles, accurately describes {l, b, v_LSR} distribution CMZ gas, is asymmetric about Sgr A* both position velocity. Velocity dispersions range...
We present a new assessment of the ability Infrared Dark Clouds (IRDCs) to form massive stars and clusters. This is done by comparison with an empirical mass–size threshold for star formation (MSF). establish m(r)>870 M☉(r/pc)1.33 as novel approximate MSF limit, based on clouds without MSF. Many IRDCs, if not most, fall short this threshold. Without significant evolution, such are unlikely candidates. provides first quantitative small number IRDCs evolving toward below limit might still...
We present 1.3mm continuum and spectral line images of two massive molecular clumps P1 P2 in the G28.34+0.06 region with Submillimeter Array. While contain masses 1000 880 \msun, respectively, has a luminosity $< 10^2$ \lsun, lower gas temperature smaller width than P2. Thus, appears to be at much earlier stage star formation The high resolution SMA observations reveal distinctive cores 97 49 respectively. 4 GHz bandpass captures emission from CO isotopologues, SO, CH$_3$OH, CH$_3$CN,...
Context.While low mass clouds have been relatively well studied, our picture of high-mass star formation remains unclear. Infrared Dark Clouds appear to be the long sought population cold and dense aggregations with potential harbouring earliest stages massive formation. Up now there has no systematic study on temperature distribution, velocity fields, chemical physical state toward this new cloud population.
We present results of 1.3 mm dust polarization observations toward 16 nearby, low-mass protostars, mapped with ~2.5" resolution at CARMA. The show that magnetic fields in protostellar cores on scales ~1000 AU are not tightly aligned outflows from the protostars. Rather, data consistent scenarios where and preferentially misaligned (perpendicular), or they randomly aligned. If one assumes emerge along rotation axes circumstellar disks, have disrupted surrounding material, then our imply disks...
The Galactic center is the closest region in which we can study star formation under extreme physical conditions like those high-redshift galaxies. We measure temperature of dense gas central molecular zone (CMZ) and examine what drives it. mapped inner 300 pc CMZ temperature-sensitive J = 3-2 para-formaldehyde (p-H$_2$CO) transitions. used $3_{2,1} - 2_{2,0} / 3_{0,3} 2_{0,2}$ line ratio to determine $n \sim 10^4 10^5 $cm$^{-3}$ gas. have produced maps cubes with 30" 1 km/s resolution...
We present a new high-resolution study of pre-protocluster regions in tracers exclusively probing the coldest and dense gas (NH_2D). The data are used to constrain chemical, thermal, kinematic, physical conditions (i.e., densities) G29.96e G35.20w. NH_3, NH_2D, continuum emission were mapped using VLA, PdBI. In particular, NH_2D is unique tracer cold, precluster at high densities, while NH_3 traces both cold warm modest-to-high densities. G29.96e, Spitzer images reveal two massive filaments,...
High-mass stars are cosmic engines known to dominate the energetics in Milky Way and other galaxies. However, their formation is still not well understood. Massive, cold, dense clouds, often appearing as infrared dark clouds (IRDCs), nurseries of massive stars. No measurements magnetic fields IRDCs a state prior onset high-mass star (HMSF) have previously been available, prevailing HMSF theories do consider strong fields. Here, we report observations two most Way. We show that G11.11−0.12...
The Central Molecular Zone (CMZ; inner $\sim{}200~\rm{}pc$) of the Milky Way is a star formation (SF) environment with very extreme physical properties. Exploration SF in this region important because (i) allows us to test models under exceptional conditions, and (ii) CMZ clouds might be suitable serve as templates understand physics starburst galaxies nearby distant universe. For reason we launched Galactic Center Cloud Survey (GCMS), first systematic study that resolves all major at...
Abstract The Survey of Water and Ammonia in the Galactic Center (SWAG) covers Central Molecular Zone (CMZ) Milky Way at frequencies between 21.2 25.4 GHz obtained Australia Telescope Compact Array ∼0.9 pc spatial ∼2.0 km s −1 spectral resolution. In this paper, we present data on inner ∼250 (1.°4) Sgr C B2. We focus hyperfine structure metastable ammonia inversion lines ( J , K ) = (1, 1)–(6, 6) to derive column density, kinematics, opacity, kinetic gas temperature. CMZ molecular clouds,...
In this paper we provide a comprehensive description of the internal dynamics G0.253+0.016 (a.k.a. 'the Brick'); one most massive and dense molecular clouds in Galaxy to lack signatures widespread star formation. As potential host future generation high-mass stars, understanding largely quiescent like is critical importance. paper, reanalyse Atacama Large Millimeter Array cycle 0 HNCO $J=4(0,4)-3(0,3)$ data at 3 mm, using two new pieces software which make available community. First,...
Abstract Magnetic fields of molecular clouds in the central zone (CMZ) have been relatively under-observed at sub-parsec resolution. Here, we report JCMT/POL2 observations polarized dust emission CMZ, which reveal magnetic field structures dense gas ∼0.5 pc The 11 our sample include two western part CMZ (Sgr C and a farside cloud candidate), four around Galactic longitude 0 (the 50 km s −1 cloud, CO 0.02−0.02, Stone , Sticks Straw among Three Little Pigs), five along Dust Ridge...
The interstellar medium in the Milky Way's Central Molecular Zone (CMZ) is known to be strongly magnetised, but its large-scale morphology and impact on gas dynamics are not well understood. We explore properties of magnetic fields CMZ using three-dimensional non-self gravitating magnetohydrodynamical simulations flow an external Way barred potential. find that: (1) field conveniently decomposed into a regular time-averaged component irregular turbulent component. aligns with velocity...
Abstract We present Atacama Large Millimeter/submillimeter Array Band 6 (1.3 mm) observations of dense cores in three massive molecular clouds within the central zone (CMZ) Milky Way, including Dust Ridge cloud e, Sgr C, and 20 km s −1 cloud, at a spatial resolution 2000 au. Among 834 identified from 1.3 mm continuum, we constrain temperatures linewidths 253 using local thermodynamic equilibrium methods to fit H 2 CO and/or CH 3 CN spectra. determine their masses dust continuum derived...
We measure the mass and size of cloud fragments in several molecular clouds continuously over a wide range spatial scales (0.05 r/pc 3).Based on recently developed "dendrogram-technique", this characterizes dense cores as well enveloping clouds."Larson's 3 rd Law" constant column density, m(r) ∝ r 2 , is not suited to describe derived mass-size data.Solar neighborhood forming massive stars ( 10 M ⊙ ; Pipe Nebula, Taurus, Perseus, Ophiuchus) obey ≤ 870 (r/pc) 1.33 .In contrast this, (Orion A,...
We present the results of combined NH3 (1,1) and (2,2) line emission observed with Very Large Array Effelsberg 100 m telescope infrared dark cloud G14.225−0.506. The reveals a network filaments constituting two hub–filament systems. Hubs are associated gas rotational temperature Trot ∼ 15 K, non-thermal velocity dispersion σNT 1 km s−1, exhibit signs star formation, while appear to be more quiescent (Trot 11 K 0.6 s−1). Filaments parallel in projection distributed mainly along directions, at...
We present the first interferometric molecular line and dust emission maps for Galactic Center (GC) cloud G0.253+0.016, observed using Combined Array Research in Millimeter--wave Astronomy (CARMA) Submillimeter (SMA). This is very dense, concentrates a mass exceeding Orion Molecular Cloud Complex (2x10^5 M_sun) into radius of only 3pc, but it essentially starless. G0.253+0.016 therefore violates "star formation laws" presently used to explain trends galactic extragalactic star by factor ~45....
We have observed the Infrared Dark Cloud (IRDC) G028.23−00.19 at 3.3 mm using Combined Array for Research in Millimeter-wave Astronomy. In its center, IRDC hosts one of most massive (∼1520 M☉) quiescent, cold (12 K) clumps known (MM1). The low temperature, high NH2D abundance, narrow molecular line widths, and absence embedded infrared sources (from 3.6 to 70 μm) indicate that clump is likely prestellar. Strong SiO emission with broad widths (6–9 km s−1) abundances ((0.8–4) × 10−9) detected...