scholarly journals SWAG Water Masers in the Galactic Center

2017 ◽  
Vol 13 (S336) ◽  
pp. 172-175
Author(s):  
Jürgen Ott ◽  
Nico Krieger ◽  
Matthew Rickert ◽  
David Meier ◽  
Adam Ginsburg ◽  
...  
Keyword(s):  
Star Formation ◽  
Galactic Center ◽  
Young Stellar Objects ◽  
Molecular Gas ◽  
Ionized Gas ◽  
Stellar Objects ◽  
Double Line ◽  
Water Masers ◽  
Sgr A ◽  
Compact Array

AbstractThe Galactic Center contains large amounts of molecular and ionized gas as well as a plethora of energetic objects. Water masers are an extinction-insensitive probe for star formation and thus ideal for studies of star formation stages in this highly obscured region. With the Australia Telescope Compact Array, we observed 22 GHz water masers in the entire Central Molecular Zone with sub-parsec resolution as part of the large SWAG survey: “Survey of Water and Ammonia in the Galactic Center”. We detect of order 600 22 GHz masers with isotropic luminosities down to ~10−7 L⊙. Masers with luminosities of ≳10−6 L⊙ are likely associated with young stellar objects. They appear to be close to molecular gas streamers and may be due to star formation events that are triggered at pericenter passages near Sgr A*. Weaker masers are more widely distributed and frequently show double line features, a tell-tale sign for an origin in evolved star envelopes.

scholarly journals Massive Star Formation Throughout the Galactic Disk

2009 ◽  
Vol 5 (H15) ◽  
pp. 798-798
Author(s):  
Stan Kurtz
Keyword(s):  
Star Formation ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Young Stellar Objects ◽  
High Mass ◽  
Molecular Gas ◽  
Mass Star ◽  
Ionized Gas ◽  
Stellar Objects ◽  
Infrared Spectral

AbstractHigh-mass star formation is manifestly a phenomenon of the Galactic Plane. The process begins with pre-stellar cores, evolves to proto-stellar objects, and culminates in massive main-sequence stars. Because massive young stellar objects are deeply embedded, the radio, sub-mm, and far/mid-infrared spectral windows are the most revealing. Galactic plane surveys at these wavelengths trace hot and cold molecular gas, interstellar masers, warm dust, and ionized gas that are present during star formation.

scholarly journals The effects of ionization feedback on star formation: a case study of the M 16 H II region

2019 ◽  
Vol 627 ◽  
pp. A27 ◽  
Author(s):  
Jin-Long Xu ◽  
Annie Zavagno ◽  
Naiping Yu ◽  
Xiao-Lan Liu ◽  
Ye Xu ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Young Stellar Objects ◽  
Ionized Gas ◽  
Stellar Objects ◽  
Multi Wavelength ◽  
The Mean ◽  
The Impact ◽  
The Relationship

Aims. We aim to investigate the impact of the ionized radiation from the M 16 H II region on the surrounding molecular cloud and on its hosted star formation. Methods. To present comprehensive multi-wavelength observations towards the M 16 H II region, we used new CO data and existing infrared, optical, and submillimeter data. The 12CO J = 1−0, 13CO J = 1−0, and C18O J = 1−0 data were obtained with the Purple Mountain Observatory (PMO) 13.7 m radio telescope. To trace massive clumps and extract young stellar objects (YSOs) associated with the M 16 H II region, we used the ATLASGAL and GLIMPSE I catalogs, respectively. Results. From CO data, we discern a large-scale filament with three velocity components. Because these three components overlap with each other in both velocity and space, the filament may be made of three layers. The M 16 ionized gas interacts with the large-scale filament and has reshaped its structure. In the large-scale filament, we find 51 compact cores from the ATLASGAL catalog, 20 of them being quiescent. The mean excitation temperature of these cores is 22.5 K, while this is 22.2 K for the quiescent cores. This high temperature observed for the quiescent cores suggests that the cores may be heated by M 16 and do not experience internal heating from sources in the cores. Through the relationship between the mass and radius of these cores, we obtain that 45% of all the cores are massive enough to potentially form massive stars. Compared with the thermal motion, the turbulence created by the nonthermal motion is responsible for the core formation. For the pillars observed towards M 16, the H II region may give rise to the strong turbulence.

scholarly journals Young stellar objects close to Sgr A*

2013 ◽  
Vol 9 (S303) ◽  
pp. 144-146
Author(s):  
B. Jalali ◽  
F. I. Pelupessy ◽  
A. Eckart ◽  
S. Portegies Zwart ◽  
N. Sabha ◽  
...  
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Radius Vector ◽  
Young Stellar Objects ◽  
Infrared Excess ◽  
Stellar Objects ◽  
Physical Conditions ◽  
Strong Compression ◽  
Sgr A ◽  
Hydrodynamical Simulations

AbstractWe aim at modeling small groups of young stars such as IRS 13N, 0.1 pc away from Sgr A*, which is suggested to contain a few embedded massive young stellar objects. We perform hydrodynamical simulations to follow the evolution of molecular clumps orbiting around a 4 × 106 M⊙ black hole, to constrain the formation and the physical conditions of such groups.We find that the strong compression due to the black hole along the orbital radius vector of clumps evolving on highly eccentric orbits causes the clumps densities to increase to higher than the tidal density of Sgr A* and required for star formation. This suggests that the tidal compression from the black hole could support star formation.Additionally, we speculate that the infrared excess source G2/DSO approaching Sgr A* on a highly eccentric orbit could be associated with a dust enshrouded star that may have been formed recently through the mechanism supported by our models.

scholarly journals Star formation in the vicinity of nuclear black holes: young stellar objects close to Sgr A*

2014 ◽  
Vol 444 (2) ◽  
pp. 1205-1220 ◽  
Author(s):  
B. Jalali ◽  
F. I. Pelupessy ◽  
A. Eckart ◽  
S. Portegies Zwart ◽  
N. Sabha ◽  
...  
Keyword(s):  
Black Holes ◽  
Star Formation ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Sgr A

scholarly journals Molecular gas and triggered star formation surrounding Wolf-Rayet stars

2012 ◽  
Vol 8 (S292) ◽  
pp. 48-48
Author(s):  
Tie Liu ◽  
Yuefang Wu ◽  
Huawei Zhang
Keyword(s):  
Star Formation ◽  
Stellar Wind ◽  
Young Stellar Objects ◽  
Molecular Gas ◽  
Number Density ◽  
Stellar Objects ◽  
Molecular Emission ◽  
Wind Velocities ◽  
Expanding Shells

AbstractThe environments surrounding nine Wolf-Rayet stars were studied in molecular emission. Expanding shells were detected surrounding these WR stars (see left panels of Figure 1). The average masses and radii of the molecular cores surrounding these WR stars anti-correlate with the WR stellar wind velocities (middle panels of Figure 1), indicating the WR stars has great impact on their environments. The number density of Young Stellar Objects (YSOs) is enhanced in the molecular shells at ∼5 arcmin from the central WR star (lower-right panel of Figure 1). Through detailed studies of the molecular shells and YSOs, we find strong evidences of triggered star formation in the fragmented molecular shells (Liu et al. 2010).

scholarly journals SWAG: Distribution and Kinematics of an Obscured AGB Population toward the Galactic Center

2018 ◽  
Vol 14 (S343) ◽  
pp. 485-486
Author(s):  
Jürgen Ott ◽  
David S. Meier ◽  
Adam Ginsburg ◽  
Farhad Yusef-Zadeh ◽  
Nico Krieger ◽  
...  
Keyword(s):  
Milky Way ◽  
Galactic Center ◽  
Mechanical Energy ◽  
Young Stellar Objects ◽  
Agb Stars ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Molecular Lines ◽  
Water Masers

AbstractOutflows from AGB stars enrich the Galactic environment with metals and inject mechanical energy into the ISM. Radio spectroscopy can recover both properties through observations of molecular lines. We present results from SWAG: “Survey of Water and Ammonia in the Galactic Center”. The survey covers the entire Central Molecular Zone (CMZ), the inner 3.35° × 0.9° (∼480 × 130 pc) of the Milky Way that contains 5 × 107 M⊙ of molecular gas. Although our survey primarily targets the CMZ, we observe across the entire sightline through the Milky Way. AGB stars are revealed by their signature of double peaked 22 GHz water maser lines. They are distinguished by their spectral signatures and their luminosities, which reach up to 10−7 L⊙. Higher luminosities are usually associated with Young Stellar Objects located in CMZ star forming regions. We detect a population of ∼600 new water masers that can likely be associated with AGB outflows.

Resolved star formation in the metal-poor star-forming region Magellanic Bridge C

2020 ◽  
Vol 499 (2) ◽  
pp. 2534-2553
Author(s):  
Venu M Kalari ◽  
Monica Rubio ◽  
Hugo P Saldaño ◽  
Alberto D Bolatto
Keyword(s):  
Star Formation ◽  
Infrared Imaging ◽  
Far Infrared ◽  
Young Stellar Objects ◽  
Molecular Gas ◽  
Stellar Objects ◽  
Filamentary Structure ◽  
Star Forming ◽  
The Galaxy ◽  
Pms Stars

ABSTRACT Magellanic Bridge C (MB-C) is a metal-poor (∼1/5 Z⊙) low-density star-forming region located 59 kpc away in the Magellanic Bridge, offering a resolved view of the star formation process in conditions different to the Galaxy. From Atacama Large Millimetre Array CO (1–0) observations, we detect molecular clumps associated with candidate young stellar objects (YSOs), pre-main sequence (PMS) stars, and filamentary structure identified in far-infrared imaging. YSOs and PMS stars form in molecular gas having densities between 17 and 200 M⊙ pc−2, and have ages between ≲0.1 and 3 Myr. YSO candidates in MB -C have lower extinction than their Galactic counterparts. Otherwise, our results suggest that the properties and morphologies of molecular clumps, YSOs, and PMS stars in MB -C present no patent differences with respect to their Galactic counterparts, tentatively alluding that the bottleneck to forming stars in regions similar to MB-C is the conversion of atomic gas to molecular.

scholarly journals Uncovering distinct environments in an extended physical system around the W33 complex

2020 ◽  
Vol 496 (2) ◽  
pp. 1278-1294 ◽  
Author(s):  
L K Dewangan ◽  
T Baug ◽  
D K Ojha
Keyword(s):  
Physical System ◽  
Large Scale ◽  
Early Stage ◽  
Young Stellar Objects ◽  
Molecular Gas ◽  
H Ii Regions ◽  
Extended System ◽  
Ionized Gas ◽  
Stellar Objects ◽  
Complementary Distribution

ABSTRACT We present a multiwavelength investigation of a large-scale physical system containing the W33 complex. The extended system (∼50 pc × 37 pc) is selected based on the distribution of molecular gas at [29.6, 60.2] km s−1 and of 88 ATLASGAL 870-μm dust clumps at d ∼2.6 kpc. The extended system/molecular cloud traced in the maps of 13CO and C18O emission contains several H ii regions excited by OB stars (age ∼0.3–1.0 Myr) and a thermally supercritical filament (fs1, length ∼17 pc). The filament, which is devoid of ionized gas, shows a dust temperature (Td) of ∼19 K, while the H ii regions have a Td of ∼21–29 K. It suggests the existence of two distinct environments in the cloud. The distribution of Class I young stellar objects (mean age ∼0.44 Myr) traces the early stage of star formation (SF) towards the cloud. At least three velocity components (around 35, 45 and 53 km s−1) are investigated towards the system. The analysis of 13CO and C18O reveals spatial and velocity connections of cloud components at around 35 and 53 km s−1. The observed positions of previously known sources, W33 Main, W33 A and O4–7I stars, are found towards a complementary distribution of these two cloud components. The filament fs1 and a previously known object W33 B are seen towards the overlapping areas of the clouds, where ongoing SF activity is evident. A scenario related to converging/colliding flows from two different velocity components appears to explain well the observed indications of SF activity in the system.

scholarly journals A radio survey of Galactic center clouds

2013 ◽  
Vol 9 (S303) ◽  
pp. 139-143
Author(s):  
E. A. C. Mills ◽  
C. C. Lang ◽  
M. R. Morris ◽  
J. Ott ◽  
N. Butterfield ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Column Density ◽  
Galactic Center ◽  
Class I ◽  
Vibrationally Excited ◽  
Density Peaks ◽  
Water Masers ◽  
Sgr A ◽  
Radio Survey

AbstractWe present a radio survey of molecules in a sample of Galactic center molecular clouds, including M0.25 + 0.01, the clouds near Sgr A, and Sgr B2. The molecules detected are primarily NH3 and HC3N; in Sgr B2-N we also detect non-metastable NH3, vibrationally-excited HC3N, torsionally-excited CH3OH, and numerous isotopologues of these species. 36 GHz Class I CH3OH masers are ubiquitous in these fields, and in several cases are associated with new NH3 (3,3) maser candidates. We also find that NH3 and HC3N are depleted or absent toward several of the highest dust column density peaks identified in submillimeter observations, which are associated with water masers and are thus likely in the early stages of star formation.

scholarly journals Large-scale star formation in Auriga region

2019 ◽  
Vol 492 (2) ◽  
pp. 2446-2467 ◽  
Author(s):  
A K Pandey ◽  
Saurabh Sharma ◽  
N Kobayashi ◽  
Y Sarugaku ◽  
K Ogura
Keyword(s):  
Star Formation ◽  
Spanning Tree ◽  
Large Scale ◽  
Minimum Spanning Tree ◽  
Young Stellar Objects ◽  
Molecular Gas ◽  
Archival Data ◽  
Stellar Objects ◽  
Tree Analysis ◽  
Formation Efficiency

ABSTRACT New observations in the VI bands along with archival data from the 2MASS and WISE surveys have been used to generate a catalogue of young stellar objects (YSOs) covering an area of about 6° × 6° in the Auriga region centred at l ∼ 173° and b ∼ 1.5°. The nature of the identified YSOs and their spatial distribution are used to study the star formation in the region. The distribution of YSOs along with that of the ionized and molecular gas reveals two ring-like structures stretching over an area of a few degrees each in extent. We name these structures as Auriga Bubbles 1 and 2. The centre of the Bubbles appears to be above the Galactic mid-plane. The majority of Class I YSOs are associated with the Bubbles, whereas the relatively older population, i.e. Class ii objects are rather randomly distributed. Using the minimum spanning tree analysis, we found 26 probable subclusters having five or more members. The subclusters are between ∼0.5 and ∼3 pc in size and are somewhat elongated. The star formation efficiency in most of the subcluster region varies between 5 ${{\ \rm per\ cent}}$ and 20 ${{\ \rm per\ cent}}$ indicating that the subclusters could be bound regions. The radii of these subclusters also support it.

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