scholarly journals An ALMA study of hub-filament systems I. On the clump mass concentration within the most massive cores

2021 ◽  
Author(s):  
Michael Anderson ◽  
Nicolas Peretto ◽  
Sarah E Ragan ◽  
Andrew J Rigby ◽  
Adam Avison ◽  
...  
Keyword(s):  
Surface Density ◽  
Mass Fraction ◽  
Massive Star ◽  
High Mass ◽  
Physical Processes ◽  
Concentrate Mass ◽  
Star Forming ◽  
Sample Bias ◽  
Significant Difference ◽  
Infrared Brightness

Abstract The physical processes behind the transfer of mass from parsec-scale clumps to massive-star-forming cores remain elusive. We investigate the relation between the clump morphology and the mass fraction that ends up in its most massive core (MMC) as a function of infrared brightness, i.e. a clump evolutionary tracer. Using ALMA 12 m and ACA we surveyed 6 infrared-dark hubs in 2.9 mm continuum at ∼3″ resolution. To put our sample into context, we also re-analysed published ALMA data from a sample of 29 high mass-surface density ATLASGAL sources. We characterise the size, mass, morphology, and infrared brightness of the clumps using Herschel and Spitzer data. Within the 6 newly observed hubs, we identify 67 cores, and find that the MMCs have masses between 15–911 M⊙ within a radius of 0.018–0.156 pc. The MMC of each hub contains 3–24 per cent of the clump mass (fMMC), becoming 5–36 per cent once core masses are normalised to the median core radius. Across the 35 clumps, we find no significant difference in the median fMMC values of hub and non-hub systems, likely the consequence of a sample bias. However, we find that fMMC is ∼7.9 times larger for infrared-dark clumps compared to infrared-bright ones. This factor increases up to ∼14.5 when comparing our sample of 6 infrared-dark hubs to infrared-bright clumps. We speculate that hub-filament systems efficiently concentrate mass within their MMC early on during its evolution. As clumps evolve, they grow in mass, but such growth does not lead to the formation of more massive MMCs.

scholarly journals ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – I. Survey description and a first look at G9.62+0.19

2020 ◽  
Vol 496 (3) ◽  
pp. 2790-2820 ◽  
Author(s):  
Tie Liu ◽  
Neal J Evans ◽  
Kee-Tae Kim ◽  
Paul F Goldsmith ◽  
Sheng-Yuan Liu ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Star Formation ◽  
Survey Data ◽  
Massive Star ◽  
High Mass ◽  
Dense Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Stellar Feedback ◽  
Dense Cores

ABSTRACT The ATOMS, standing for ALMA Three-millimeter Observations of Massive Star-forming regions, survey has observed 146 active star-forming regions with ALMA band 3, aiming to systematically investigate the spatial distribution of various dense gas tracers in a large sample of Galactic massive clumps, to study the roles of stellar feedback in star formation, and to characterize filamentary structures inside massive clumps. In this work, the observations, data analysis, and example science of the ATOMS survey are presented, using a case study for the G9.62+0.19 complex. Toward this source, some transitions, commonly assumed to trace dense gas, including CS J = 2−1, HCO+J = 1−0, and HCN J = 1−0, are found to show extended gas emission in low-density regions within the clump; less than 25 per cent of their emission is from dense cores. SO, CH3OH, H13CN, and HC3N show similar morphologies in their spatial distributions and reveal well the dense cores. Widespread narrow SiO emission is present (over ∼1 pc), which may be caused by slow shocks from large–scale colliding flows or H ii regions. Stellar feedback from an expanding H ii region has greatly reshaped the natal clump, significantly changed the spatial distribution of gas, and may also account for the sequential high-mass star formation in the G9.62+0.19 complex. The ATOMS survey data can be jointly analysed with other survey data, e.g. MALT90, Orion B, EMPIRE, ALMA_IMF, and ALMAGAL, to deepen our understandings of ‘dense gas’ star formation scaling relations and massive protocluster formation.

scholarly journals Is there a cluster in the massive star forming region IRAS 20126+4104?

2015 ◽  
Vol 12 (S316) ◽  
pp. 157-158
Author(s):  
V. A. Montes ◽  
Peter Hofner ◽  
C. Anderson ◽  
V. Rosero
Keyword(s):  
Surface Density ◽  
Massive Star ◽  
Radio Observation ◽  
Large Array ◽  
Very Large Array ◽  
X Ray ◽  
Star Forming ◽  
Continuum Radio

AbstractA Chandra X-ray Observatory ACIS-I observation and a 6 cm continuum radio observation with the Karl G. Jansky Very Large Array (VLA) together with a multiwavelength study in infrared (2MASS and Spitzer) and optical (USNO-B1.0) shows an increasing surface density of X-ray sources toward the massive protostar. There are at least 43 YSOs within 1.2 pc distance from the massive protostar. This number is consistent with typical B-type stars clusters (Lada & Lada 2003).

scholarly journals VLBI multi-epoch water maser observations toward massive protostars

2012 ◽  
Vol 8 (S287) ◽  
pp. 377-385 ◽  
Author(s):  
José M. Torrelles ◽  
José F. Gómez ◽  
Nimesh A. Patel ◽  
Salvador Curiel ◽  
Guillem Anglada ◽  
...  
Keyword(s):  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Central Engine ◽  
Dynamic Scenario ◽  
Low Mass ◽  
Cepheus A ◽  
Water Maser

AbstractVLBI multi-epoch water maser observations are a powerful tool to study the gas very close to the central engine responsible for the phenomena associated with the early evolution of massive protostars. In this paper we present a summary of the main observational results obtained toward the massive star-forming regions of Cepheus A and W75N. These observations revealed unexpected phenomena in the earliest stages of evolution of massive objects (e.g., non-collimated “short-lived” pulsed ejections in different massive protostars), and provided new insights in the study of the dynamic scenario of the formation of high-mass stars (e.g., simultaneous presence of a jet and wide-angle outflow in the massive object Cep A HW2, similar to what is observed in low-mass protostars). In addition, with these observations it has been possible to identify new, previously unseen centers of high-mass star formation through outflow activity.

scholarly journals 325 GHz Water Masers in Orion Source I

2012 ◽  
Vol 8 (S287) ◽  
pp. 184-185
Author(s):  
Florian Niederhofer ◽  
Elizabeth Humphreys ◽  
Ciriaco Goddi ◽  
Lincoln J. Greenhill
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Compact Disk ◽  
Volume Source ◽  
Star Forming ◽  
Star Forming Regions ◽  
Water Masers ◽  
Excitation Conditions

AbstractRadio Source I in the Orion BN/KL region provides the closest example of high mass star formation. It powers a rich ensemble of SiO and H2O masers, and is one of only three star-forming regions known to display SiO maser emission. Previous monitoring of different SiO masers with the VLBA and VLA has enabled the resolution of a compact disk and a protostellar wind at radii <100 AU from Source I, which collimates into a bipolar outflow at radii of 100-1000 AU (see contribution by Greenhill et al., this volume). Source I may provide the best case of disk-mediated accretion and outflow recollimation in massive star formation. Here, we report preliminary results of sub-arcsecond resolution 325 GHz H2O maser observations made with the SMA. We find that 325 GHz H2O masers trace a more collimated portion of the Source I outflow than masers at 22 GHz, but occur at similar radii suggesting similar excitation conditions. A velocity gradient perpendicular to the outflow axis, indicating rotation, supports magneto-centrifugal driving of the flow.

scholarly journals Effects of infall and outflow on massive star-forming regions

2019 ◽  
Vol 488 (4) ◽  
pp. 4638-4647 ◽  
Author(s):  
Qiang Li ◽  
Jianjun Zhou ◽  
Jarken Esimbek ◽  
Yuxin He ◽  
Willem Baan ◽  
...  
Keyword(s):  
Detection Rate ◽  
Massive Star ◽  
Local Environment ◽  
Intimate Relationship ◽  
High Mass ◽  
Evolutionary Time ◽  
Star Forming ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Water Masers

ABSTRACT A total of 188 high-mass outflows have been identified from a sample of 694 clumps from the Millimetre Astronomy Legacy Team 90 GHz survey, representing a detection rate of approximately 27 per cent. The detection rate of outflows increases from the proto-stellar stage to the H ii stage, but decreases again at the photodissociation (PDR) stage suggesting that outflows are being switched off during the PDR stage. An intimate relationship is found between outflow action and the presence of masers, and water masers appear together with 6.7 GHz methanol masers. Comparing the infall detection rate of clumps with and without outflows, we find that outflow candidates have a lower infall detection rate. Finally, we find that outflow action has some influence on the local environment and the clump itself, and this influence decreases with increasing evolutionary time as the outflow action ceases.

scholarly journals New Constraints on the 12CO(2 − 1)/(1 − 0) Line Ratio Across Nearby Disc Galaxies

2021 ◽  
Author(s):  
J S den Brok ◽  
D Chatzigiannakis ◽  
F Bigiel ◽  
J Puschnig ◽  
A T Barnes ◽  
...  
Keyword(s):  
Surface Density ◽  
Massive Star ◽  
Formation Rate ◽  
Molecular Gas ◽  
Star Forming ◽  
Large Program ◽  
The Galaxy ◽  
The Mean ◽  
Point To Point ◽  
Disc Galaxies

Abstract Both the CO(2-1) and CO(1-0) lines are used to trace the mass of molecular gas in galaxies. Translating the molecular gas mass estimates between studies using different lines requires a good understanding of the behaviour of the CO(2-1)-to-CO(1-0) ratio, R21. We compare new, high quality CO(1-0) data from the IRAM 30-m EMPIRE survey to the latest available CO(2-1) maps from HERACLES, PHANGS-ALMA, and a new IRAM 30-m M51 Large Program. This allows us to measure R21 across the full star-forming disc of nine nearby, massive, star-forming spiral galaxies at 27″(∼1 − 2 kpc) resolution. We find an average R21 = 0.64 ± 0.09 when we take the luminosity-weighted mean of all individual galaxies. This result is consistent with the mean ratio for disc galaxies that we derive from single-pointing measurements in the literature, $R_{\rm 21, lit}~=~0.59^{+0.18}_{-0.09}$. The ratio shows weak radial variations compared to the point-to-point scatter in the data. In six out of nine targets the central enhancement in R21 with respect to the galaxy-wide mean is of order $\sim 10{-}20\%$. We estimate an azimuthal scatter of ∼20% in R21 at fixed galactocentric radius but this measurement is limited by our comparatively coarse resolution of 1.5 kpc. We find mild correlations between R21 and CO brightness temperature, IR intensity, 70-to-160 μm ratio, and IR-to-CO ratio. All correlations indicate that R21 increases with gas surface density, star formation rate surface density, and the interstellar radiation field.

scholarly journals Methanol masers: Evolutionary and kinematic tracers of massive star formation

2002 ◽  
Vol 206 ◽  
pp. 147-150
Author(s):  
Vincent Minier ◽  
Roy Booth ◽  
John Conway ◽  
Michele Pestalozzi
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Vlbi Observations ◽  
Methanol Masers ◽  
Maser Sources

We summarise our recent VLBI observations of a large sample of methanol maser sources associated with high-mass star-forming regions.

scholarly journals Massive star-formation toward G28.87+0.07

2012 ◽  
Vol 8 (S287) ◽  
pp. 180-181
Author(s):  
J. J. Li ◽  
L. Moscadelli ◽  
R. Cesaroni ◽  
R. S. Furuya ◽  
Y. Xu ◽  
...  
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Young Star ◽  
Observational Evidence ◽  
High Mass ◽  
Mass Star ◽  
Massive Star Formation ◽  
Stellar Cluster ◽  
Star Forming ◽  
Infrared Continuum

AbstractWe investigated the high-mass star-forming region G28.87+0.07 by means of maser kinematics, including H2O, CH3OH, and OH, and radio to infrared, continuum observations. All observational evidence suggests that these masers are associated with the same young star of 20-30 M⊙, still in the main accretion phase and surrounded by a rich stellar cluster.

Probing Early Phases of High Mass Stars with 6.7 GHz Methanol Masers

2017 ◽  
Vol 13 (S336) ◽  
pp. 323-324
Author(s):  
Sonu Tabitha Paulson ◽  
Jagadheep D. Pandian
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Dust Emission ◽  
Black Body ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Early Phases

AbstractMethanol masers at 6.7 GHz are the brightest of class II methanol masers and have been found exclusively towards massive star forming regions. These masers can thus be used as a unique tool to probe the early phases of massive star formation. We present here the SED studies of 284 methanol masers chosen from the MMB catalogue, which falls in the Hi-GAL range (|l| ≤ 60°, |b| ≤ 1°). The masers are studied using the ATLASGAL, MIPSGAL and Hi-GAL data at wavelengths ranging from 24−870 micrometers. A single grey body component fit was used to model the cold dust emission whereas the emission from the warm dust is modelled by a black body. The clump properties such as isothermal mass, FIR luminosity and MIR luminosity were obtained using the best fit parameters of the SED fits. We discuss the physical properties of the sources and explore the evolutionary stages of the sources having 6.7 GHz maser emission in the timeline of high mass star formation.

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