Probing GLIMPSE Extended Green Objects (EGOs) with hydroxyl masers

2020 ◽  
Vol 499 (3) ◽  
pp. 3961-3975
Author(s):  
O S Bayandina ◽  
P Colom ◽  
S E Kurtz ◽  
G M Rudnitskij ◽  
N N Shakhvorostova ◽  
...  
Keyword(s):  
Detection Rate ◽  
Infrared Emission ◽  
Radio Continuum ◽  
High Mass ◽  
Continuum Emission ◽  
Maser Emission ◽  
Very Large Array ◽  
Methanol Masers ◽  
Cent Detection

ABSTRACT We present a study of 18 cm OH maser emission toward 20 high-mass young stellar object outflow candidates (Extended Green Objects, EGOs) identified from the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE). All four OH ground state lines at 1612, 1665, 1667, and 1720 MHz, together with 20-cm continuum emission, were observed with the Karl G. Jansky Very Large Array C-configuration. Follow-up polarimetric single-dish observations with the Nançay radio telescope were performed for the same OH transitions, except 1612 MHz. OH maser emission is found to be an uncommon feature of the sample, with a 50 per cent detection rate for the entire sample and a ∼44 per cent detection rate for the ‘likely’ EGOs. No 20-cm continuum emission is detected toward any of the sources. In most cases, the detected OH maser emission arises in vicinity to compact central sources; OH masers coexist with the 6.7 GHz methanol masers, but are found in more diffuse and extended halo-shaped regions of several thousand astronomical units in size. Comparing EGO samples with OH maser detection and non-detection, EGOs showing OH maser emission tend to have lower dust clump masses, but higher 24 and 4.5 μm flux densities. Thus, OH maser emission might be an indicator of more evolved EGOs, since strong compact mid-infrared emission in the absence of compact radio continuum emission is thought to be associated with the later stage of massive star formation.

scholarly journals A 12.2 GHz Methanol Maser Survey toward the 6.7 GHz Counterparts Associated with/without UC H ii Regions

2022 ◽  
Vol 258 (1) ◽  
pp. 19
Author(s):  
Shi-Min Song ◽  
Xi Chen ◽  
Zhi-Qiang Shen ◽  
Bin Li ◽  
Kai Yang ◽  
...  
Keyword(s):  
Detection Rate ◽  
Radio Continuum ◽  
Young Stellar Objects ◽  
High Mass ◽  
Continuum Emission ◽  
H Ii Regions ◽  
Stellar Objects ◽  
Methanol Maser ◽  
Physical Environments ◽  
Methanol Masers

Abstract We report a new survey of the 12.2 GHz Class II methanol masers toward a sample of 367 sources with the 6.7 GHz methanol masers conducted with the Shanghai 65 m Tianma Radio Telescope. This sample has been previously made with observations of the radio continuum emission of UC H ii regions by the VLA. A total of 176 sources were detected with the 12.2 GHz methanol maser, with a detection rate of 48%, including 8 new detections. A lower detection rate (<10%) was determined toward the sources in the Galactic longitude ranges of 60°–180°, revealing that the physical environments from those sources in the Local arm or the tails of Galactic arms do not easily excite the 12.2 GHz masers. In addition, two detections of highly excited-state OH masers at the 13.4 GHz transition were made, one of which is a new detection. Compared to previous surveys, one-third of the detected 12.2 GHz masers show considerable flux variations, implying the possible changes of their physical environments associated with variable radiation fields from their host high-mass young stellar objects. A positive log–log correlation is found between the luminosities of the 6.7 and 12.2 GHz masers in our observed sample, suggesting that both the transition masers have similar excitation conditions. The statistical analysis for the relationships between the methanol maser luminosity and UC H ii region spatial size indicates that the maser luminosities of both the 6.7 and 12.2 GHz transitions have a decreasing trend with the spatial sizes of the associated UC H ii regions, indicating that the Class II methanol masers might fade away with the H ii region evolution.

A new jet/outflow maser in the nucleus of the Compton-thick AGN IRAS 15480-0344

2017 ◽  
Vol 13 (S336) ◽  
pp. 129-132
Author(s):  
Paola Castangia ◽  
Andrea Tarchi ◽  
Alessandro Caccianiga ◽  
Paola Severgnini ◽  
Gabriele Surcis ◽  
...  
Keyword(s):  
Detection Rate ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Maser Emission ◽  
X Ray ◽  
Vlbi Observations ◽  
S0 Galaxies ◽  
Water Maser

AbstractInvestigations of H2O maser galaxies at X-ray energies reveal that most harbor highly absorbed AGN. Possible correlations between the intrinsic X-ray luminosity and the properties of water maser emission have been suggested. With the aim of looking into these correlations on a more solid statistical basis, we have search for maser emission in a well-defined sample of Compton-thick AGN. Here we report the results of the survey, which yielded a surprisingly high maser detection rate, with a particular focus on the newly discovered luminous water maser in the lenticular (field) S0 galaxy IRAS 15480-0344. Recently, VLBI observations have been obtained to image the line and continuum emission in the nucleus of this galaxy. The radio continuum emission at VLBI scales is resolved into two compact components that are interpreted as jet knots. Based on the single-dish profile, the variability of the maser emission, and the position of the maser spots with respect to these continuum sources, we favor of a jet/outflow origin for the maser emission, consistent with similar cases found in other radio-quiet AGN. This scenario is consistent with the hypothesis of the presence of strong nuclear winds recently invoked to explain the main characteristics of field S0 galaxies.

scholarly journals Triggered high-mass star formation in the H ii region W 28 A2: A cloud–cloud collision scenario

2020 ◽  
Author(s):  
Katsuhiro Hayashi ◽  
Satoshi Yoshiike ◽  
Rei Enokiya ◽  
Shinji Fujita ◽  
Rin Yamada ◽  
...  
Keyword(s):  
Star Formation ◽  
Intensity Ratio ◽  
Molecular Clouds ◽  
Early Stage ◽  
Infrared Emission ◽  
Radio Continuum ◽  
High Mass ◽  
Continuum Emission ◽  
Mass Star ◽  
H Ii Region

Abstract We report on a study of the high-mass star formation in the H ii region W 28 A2 by investigating the molecular clouds that extend over ∼5–10 pc from the exciting stars using the 12CO and 13CO (J = 1–0) and 12CO (J = 2–1) data taken by NANTEN2 and Mopra observations. These molecular clouds consist of three velocity components with CO intensity peaks at VLSR ∼ −4 km s−1, 9 km s−1, and 16 km s−1. The highest CO intensity is detected at VLSR ∼ 9 km s−1, where the high-mass stars with spectral types O6.5–B0.5 are embedded. We found bridging features connecting these clouds toward the directions of the exciting sources. Comparisons of the gas distributions with the radio continuum emission and 8 μm infrared emission show spatial coincidence/anti-coincidence, suggesting physical associations between the gas and the exciting sources. The 12CO J = 2–1 to 1–0 intensity ratio shows a high value (≳0.8) toward the exciting sources for the −4 km s−1 and +9 km s−1 clouds, possibly due to heating by the high-mass stars, whereas the intensity ratio at the CO intensity peak (VLSR ∼ 9 km s−1) decreases to ∼0.6, suggesting self absorption by the dense gas in the near side of the +9 km s−1 cloud. We found partly complementary gas distributions between the −4 km s−1 and +9 km s−1 clouds, and the −4 km s−1 and +16 km s−1 clouds. The exciting sources are located toward the overlapping region in the −4 km s−1 and +9 km s−1 clouds. Similar gas properties are found in the Galactic massive star clusters RCW 38 and NGC 6334, where an early stage of cloud collision to trigger the star formation is suggested. Based on these results, we discuss the possibility of the formation of high-mass stars in the W 28 A2 region being triggered by cloud–cloud collision.

scholarly journals The infrared environments of masers associated with star formation

2007 ◽  
Vol 3 (S242) ◽  
pp. 102-109
Author(s):  
James De Buizer
Keyword(s):  
Accretion Disks ◽  
Near Infrared ◽  
Hii Regions ◽  
Radio Continuum ◽  
High Mass ◽  
Dense Medium ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Methanol Masers ◽  
Ir Emission

AbstractThe near infrared (1–2μm) and the thermal infrared (3–25μm) trace many of the environments in which masers are thought to reside, including shocks, outflows, accretion disks, and the dense medium near protostars. After a number of recent surveys it has been found that there is a higher detection rate of mid-IR emission towards masers than cm radio continuum emission from UC HII regions, and that the mid-IR emission is actually more closely cospatial to the maser locations. A high percentage of water and methanol masers that are not coincident with the UC HII regions in massive star forming regions are likely to be tracing outflows and extremely young high mass stars before the onset of the UC HII region phase. After a decade of groundwork supporting the hypothesis that linearly distributed class II methanol masers may generally trace accretion disks around young massive stars, compelling evidence is mounting that these masers may generally be associated with outflows instead. Substantiation of this claim comes from recent outflow surveys and high angular resolution mid-IR imaging of the maser environments.

scholarly journals Millimetre wavelength methanol masers survey towards massive star forming regions

2007 ◽  
Vol 3 (S242) ◽  
pp. 234-235
Author(s):  
T. Umemoto ◽  
N. Mochizuki ◽  
K. M. Shibata ◽  
D.-G. Roh ◽  
H.-S. Chung
Keyword(s):  
Detection Rate ◽  
Massive Star ◽  
Molecular Line ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Maser Sources

AbstractWe present the results of a mm wavelength methanol maser survey towards massive star forming regions. We have carried out Class II methanol maser observations at 86.6 GHz, 86.9 GHz and 107.0 GHz, simultaneously, using the Nobeyama 45 m telescope. We selected 108 6.7 GHz methanol maser sources with declinations above −25 degrees and fluxes above 20 Jy. The detection limit of maser observations was ~3 Jy. Of the 93 sources surveyed so far, we detected methanol emission in 25 sources (27%) and “maser” emission in nine sources (10%), of which thre “maser” sources are new detections. The detection rate for maser emission is about half that of a survey of the southern sky (Caswell et al. 2000). There is a correlation between the maser flux of 107 GHz and 6.7 GHz/12 GHz emission, but no correlation with the “thermal” (non maser) emission. From results of other molecular line observations, we found that the sources with methanol emission show higher gas temperatures and twice the detection rate of SiO emission. This may suggest that dust evaporation and destruction by shock are responsible for the high abundance of methanol molecules, one of the required physical conditions for maser emission.

scholarly journals Class I methanol masers in the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 147-149
Author(s):  
L. O. Sjouwerman ◽  
Y. M. Pihlström
Keyword(s):  
Galactic Center ◽  
Class I ◽  
Large Array ◽  
Maser Emission ◽  
Very Large Array ◽  
Sagittarius A ◽  
Current Location ◽  
Theoretical Predictions ◽  
Methanol Masers ◽  
Sgr A

AbstractWe report on the detection of 36 and 44 GHz Class I methanol (CH3OH) maser emission in the Sagittarius A (Sgr A) complex with the Karl G. Jansky Very Large Array (VLA). These VLA observations show that the Sgr A complex harbors at least three different maser tracers of shocked regions in the radio regime. The 44 GHz masers correlate with the positions and velocities of previously detected 36 GHz CH3OH masers, but less with 1720 MHz OH masers. Our detections agree with theoretical predictions that the densities and temperatures conducive for 1720 MHz OH masers may also produce 36 and 44 GHz CH3OH maser emission. However, many 44 GHz masers do not overlap with 36 GHz methanol masers, suggesting that 44 GHz masers also arise in regions too hot and too dense for 36 GHz masers to form. This agrees with the non-detection of 1720 MHz OH masers in the same area, which are thought to be excited under even cooler and less dense conditions. We speculate that the geometry of the 36 GHz masers outlines the current location of a shock front.

scholarly journals Water maser and radio continuum emission towards IRAS 23139+5939

2007 ◽  
Vol 3 (S242) ◽  
pp. 180-181
Author(s):  
M. A. Trinidad ◽  
S. Curiel ◽  
J. M. Torrelles ◽  
L. F. Rodríguez ◽  
V. Migenes ◽  
...  
Keyword(s):  
Flux Density ◽  
Line Emission ◽  
The Other ◽  
Radio Continuum ◽  
High Mass ◽  
Continuum Emission ◽  
Maser Line ◽  
Water Masers ◽  
Water Maser ◽  
The Continuum

AbstractWe present simultaneous observations of continuum (3.5 and 1.3cm) and water maser line emission (1.3cm) carried out with the VLA-A toward the high-mass object IRAS 23139+5939. We detected two radio continuum sources at 3.5cm separated by 0”5 (~2400 AU), I23139 and I23139S. Based on the observed continuum flux density and the spectral index, we suggest that I23139 is a thermal radio jet associated with a high-mass YSO. On the other hand, based on the spatio-kinematical distribution of the water masers, together with the continuum emission information, we speculate that I23139S is also a jet source powering some of the masers detected in the region.

scholarly journals Quasi-simultaneous Radio/X-Ray Observations of the Candidate Transitional Millisecond Pulsar 3FGL J1544.6−1125 during its Low-luminosity Accretion-disk State

2021 ◽  
Vol 923 (1) ◽  
pp. 3
Author(s):  
Amruta D. Jaodand ◽  
Adam T. Deller ◽  
Nina Gusinskaia ◽  
Jason W. T. Hessels ◽  
James C. A. Miller-Jones ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Large Array ◽  
Millisecond Pulsar ◽  
Very Large Array ◽  
X Ray ◽  
Upper Limit ◽  
5 Ghz ◽  
Variable Radio

Abstract 3FGL J1544.6−1125 is a candidate transitional millisecond pulsar (tMSP). Similar to the well-established tMSPs—PSR J1023+0038, IGR J18245−2452, and XSS J12270−4859—3FGL J1544.6−1125 shows γ-ray emission and discrete X-ray “low” and “high” modes during its low-luminosity accretion-disk state. Coordinated radio/X-ray observations of PSR J1023+0038 in its current low-luminosity accretion-disk state showed rapidly variable radio continuum emission—possibly originating from a compact, self-absorbed jet, the “propellering” of accretion material, and/or pulsar moding. 3FGL J1544.6−1125 is currently the only other (candidate) tMSP system in this state, and can be studied to see whether tMSPs are typically radio-loud compared to other neutron star binaries. In this work, we present a quasi-simultaneous Very Large Array and Swift radio/X-ray campaign on 3FGL J1544.6−1125. We detect 10 GHz radio emission varying in flux density from 47.7 ± 6.0 μJy down to ≲15 μJy (3σ upper limit) at four epochs spanning three weeks. At the brightest epoch, the radio luminosity is L 5 GHz = (2.17 ± 0.17) × 1027 erg s−1 for a quasi-simultaneous X-ray luminosity L 2–10 keV = (4.32 ± 0.23) × 1033 erg s−1 (for an assumed distance of 3.8 kpc). These luminosities are close to those of PSR J1023+0038, and the results strengthen the case that 3FGL J1544.6−1125 is a tMSP showing similar phenomenology to PSR J1023+0038.

scholarly journals Investigation of the cosmic ray population and magnetic field strength in the halo of NGC 891

2018 ◽  
Vol 615 ◽  
pp. A98 ◽  
Author(s):  
D. D. Mulcahy ◽  
A. Horneffer ◽  
R. Beck ◽  
M. Krause ◽  
P. Schmidt ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Low Frequency ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Low Frequencies ◽  
Very Large Array ◽  
Field Strengths

Context. Cosmic rays and magnetic fields play an important role for the formation and dynamics of gaseous halos of galaxies. Aims. Low-frequency radio continuum observations of edge-on galaxies are ideal to study cosmic-ray electrons (CREs) in halos via radio synchrotron emission and to measure magnetic field strengths. Spectral information can be used to test models of CRE propagation. Free–free absorption by ionized gas at low frequencies allows us to investigate the properties of the warm ionized medium in the disk. Methods. We obtained new observations of the edge-on spiral galaxy NGC 891 at 129–163 MHz with the LOw Frequency ARray (LOFAR) and at 13–18 GHz with the Arcminute Microkelvin Imager (AMI) and combine them with recent high-resolution Very Large Array (VLA) observations at 1–2 GHz, enabling us to study the radio continuum emission over two orders of magnitude in frequency. Results. The spectrum of the integrated nonthermal flux density can be fitted by a power law with a spectral steepening towards higher frequencies or by a curved polynomial. Spectral flattening at low frequencies due to free–free absorption is detected in star-forming regions of the disk. The mean magnetic field strength in the halo is 7 ± 2 μG. The scale heights of the nonthermal halo emission at 146 MHz are larger than those at 1.5 GHz everywhere, with a mean ratio of 1.7 ± 0.3, indicating that spectral ageing of CREs is important and that diffusive propagation dominates. The halo scale heights at 146 MHz decrease with increasing magnetic field strengths which is a signature of dominating synchrotron losses of CREs. On the other hand, the spectral index between 146 MHz and 1.5 GHz linearly steepens from the disk to the halo, indicating that advection rather than diffusion is the dominating CRE transport process. This issue calls for refined modelling of CRE propagation. Conclusions. Free–free absorption is probably important at and below about 150 MHz in the disks of edge-on galaxies. To reliably separate the thermal and nonthermal emission components, to investigate spectral steepening due to CRE energy losses, and to measure magnetic field strengths in the disk and halo, wide frequency coverage and high spatial resolution are indispensable.

scholarly journals High Resolution Radio Continuum Observations of High Mass Star Formation Regions

2001 ◽  
Vol 205 ◽  
pp. 280-281
Author(s):  
S. Kurtz ◽  
P. Hofner ◽  
C. Vargas ◽  
W. Díaz-Merced
Keyword(s):  
Star Formation ◽  
Radio Continuum ◽  
High Mass ◽  
High Angular Resolution ◽  
Mass Star ◽  
High Quality ◽  
Very Large Array ◽  
Adverse Conditions ◽  
Star Formation Regions ◽  
Calibration Techniques

We present high angular resolution centimeter and millimeter continuum observations of several galactic massive star formation regions. Using calibration techniques pioneered at the Very Large Array, we are able to obtain high quality images even under adverse conditions of phase stability. Techniques such as these will be essential if future millimeter arrays are to obtain high quality and high precision images. We provide a current summary of our on-going survey, and present images and a brief discussion of several of the more intriguing sources.

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