scholarly journals Continuum Wavelength Emission from Embedded, Young, and Massive Stellar Objects Beyond 1 μm

1990 ◽  
Vol 139 ◽  
pp. 113-114
Author(s):  
Thomas Henning ◽  
Werner Pfau
Keyword(s):  
Molecular Clouds ◽  
Dust Emission ◽  
Average Energy ◽  
Hii Regions ◽  
Point Sources ◽  
Color Temperature ◽  
Stellar Objects ◽  
Ob Stars ◽  
Infrared Background ◽  
Wavelength Emission

One of the components of the galactic infrared background (GIRB) radiation is emission by warm dust grains heated by OB stars embedded in molecular clouds. The main contributors are compact HII regions and comparatively radioquiet infrared (IR) point sources such as the Becklin-Neugebauer object. We present the average energy distribution between 1 and 1300 μm for a sample of BN-type objects. The average color temperature between 60 and 100 μm is ~40 K, which is very similar to the color temperature of the observed warm galactic dust emission (WGDE).

scholarly journals Hα emission-line stars in molecular clouds

2019 ◽  
Vol 630 ◽  
pp. A90 ◽  
Author(s):  
Bertil Pettersson ◽  
Bo Reipurth
Keyword(s):  
Molecular Clouds ◽  
Young Stellar Objects ◽  
Be Stars ◽  
Stellar Objects ◽  
Strong Concentration ◽  
Ob Stars ◽  
Star Forming ◽  
Hα Emission ◽  
Objective Prism ◽  
Emission Stars

A deep objective-prism survey for Hα emission stars towards the Canis Major star-forming clouds was performed. A total of 398 Hα emitters were detected, 353 of which are new detections. There is a strong concentration of these Hα emitters towards the molecular clouds surrounding the CMa OB1 association, and it is likely that these stars are young stellar objects recently born in the clouds. An additional population of Hα emitters is scattered all across the region, and probably includes unrelated foreground dMe stars and background Be stars. About 90% of the Hα emitters are detected by WISE, of which 75% was detected with usable photometry. When plotted in a WISE colour–colour diagram it appears that the majority are Class II YSOs. Coordinates and finding charts are provided for all the new stars, and coordinates for all the detections. We searched the Gaia-DR2 catalogue and from 334 Hα emission stars with useful parallaxes, we selected a subset of 98 stars that have parallax errors of less than 20% and nominal distances in the interval 1050 to 1350 pc that surrounds a strong peak at 1185 pc in the distance distribution. Similarly, Gaia distances were obtained for 51 OB-stars located towards Canis Major and selected with the same parallax errors as the Hα stars. We find a median distance for the OB stars of 1182 pc, in excellent correspondence with the distance from the Hα stars. Two known runaway stars are confirmed as members of the association. Finally, two new Herbig-Haro objects are identified.

scholarly journals The RMS survey: radio observations of candidate massive YSOs in the southern hemisphere

2006 ◽  
Vol 2 (S237) ◽  
pp. 482-482 ◽  
Author(s):  
J. S. Urquhart ◽  
A. L. Busfield ◽  
M. G. Hoare ◽  
S. L. Lumsden ◽  
A. J. Clarke ◽  
...  
Keyword(s):  
Hii Regions ◽  
Point Sources ◽  
Radio Continuum ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Evolved Stars ◽  
Multi Wavelength ◽  
Sources Of Contamination ◽  
Compact Array

AbstractThe Red MSX Source (RMS) survey (Hoare et al. 2005) is a multi-wavelength programme of follow-up observations designed to distinguish between genuine massive young stellar objects (MYSOs) and other embedded or dusty objects, such as ultra compact (UC) HII regions, evolved stars and planetary nebulae (PNe). We have identified nearly 2000 MYSOs candidates by comparing the colours of MSX and 2MASS point sources to those of known MYSOs. There are several other types of embedded or dust enshrouded objects that have similar colours as MYSOs and contaminate our sample. Two sources of contamination are from UCHII regions and PNe, both of which can be identified from the radio emission emitted by their ionised nebulae. In order to identify UCHII regions and PNe that contaminate our sample we have conducted high resolution radio continuum observations at 3.6 and 6 cm of all southern MYSOs candidates (235° < l < 350°) using the Australia Telescope Compact Array (ATCA).

Molecular Clouds and Star Formation in the Southern H II Regions

1999 ◽  
Vol 51 (6) ◽  
pp. 791-818 ◽  
Author(s):  
Reiko Yamaguchi ◽  
Hiro Saito ◽  
Norikazu Mizuno ◽  
Yoshihiro Mine ◽  
Akira Mizuno ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Formation Rate ◽  
Point Sources ◽  
Young Stellar Objects ◽  
H Ii Regions ◽  
Stellar Objects ◽  
Order Of Magnitude ◽  
Formation Efficiency ◽  
Active Formation

Abstract We have carried out extensive 13CO(J = 1−0) observations toward 23 southern H II regions associated with bright-rimmed clouds. In total, 95 molecular clouds have been identified to be associated with the H II regions. Among the 95, 57 clouds \ are found to be associated with 204 IRAS point sources which are candidates for young stellar objects. There is a significant increase of star-formation efficiency on the side facing to the H II regions; the luminosity-to-mass ratio, defined as the ratio of the stellar luminosity to the molecular cloud mass, is higher by an order of magnitude on the near side of the H II regions than that on the far side. This indicates that molecular gas facing to the H II regions is more actively forming massive s\ tars whose luminosity is ≳103L⊙. In addition, the number density of the IRAS point sources increases by a factor of 2 on the near side of the H II regions compared with on the far side. These results strongly suggest that the active formation of massive stars on the near side of the H II regions is due to the effects of the H II regions, such as the compression of molecular material by the ionization/shock fronts. For the whole Galaxy, we estimate that the present star-formation rate under such effects is at least 0.2−0.4 M⊙ yr-1, corresponding to a few 10% by mass.

scholarly journals Dense molecular clouds and associated star formation in the Magellanic Clouds

2006 ◽  
Vol 2 (S237) ◽  
pp. 40-46
Author(s):  
Mónica Rubio
Keyword(s):  
Star Formation ◽  
Uv Radiation ◽  
Molecular Clouds ◽  
Massive Star ◽  
Dust Emission ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Giant Molecular Clouds ◽  
Stellar Objects ◽  
Ir Sources

AbstractMultiwavelengths studies of massive star formation regions in the LMC and SMC reveal that a second generation of stars is being formed in dense molecular clouds located in the surroundings of the massive clusters. These dense molecular clouds have survived the action of massive star UV radiation fields and winds and they appear as compact dense H2 knots in regions of weak CO emission. Alternatively, we have found that large molecular clouds, probably remnants of the parental giant molecular clouds where the first generation of stars were formed, are suffering the interaction of the winds and UV radiation field in their surfaces in the direction of the central massive cluster or massive stars. These molecular regions show 1.2 mm continuum emission form cold dust and they show embedded IR sources as determined from deep ground base JHKs imaging. The distribution of young IR sources as determined from their Mid IR colors obtained by SPITZER concentrate in the maxima of CO and dust emission. IR spectroscopy of the embedded sources with high IR excess confirm their nature as massive young stellar objects (MYSO's). Our results are suggestive of contagious star formation where triggering and induced star formation could be taking place.

scholarly journals Gathering dust: A galaxy-wide study of dust emission from cloud complexes in NGC 300

2018 ◽  
Vol 612 ◽  
pp. A81 ◽  
Author(s):  
M. Riener ◽  
C. M. Faesi ◽  
J. Forbrich ◽  
C. J. Lada
Keyword(s):  
Molecular Clouds ◽  
Dust Emission ◽  
Hii Regions ◽  
High Mass ◽  
Stellar Disk ◽  
Mass Star ◽  
Final Size ◽  
Total Dust ◽  
Dust Mass ◽  
Cold Dust

Aims. We use multi-band observations by the Herschel Space Observatory to study the dust emission properties of the nearby spiral galaxy NGC 300. We compile a first catalogue of the population of giant dust clouds (GDCs) in NGC 300, including temperature and mass estimates, and give an estimate of the total dust mass of the galaxy. Methods. We carried out source detection with the multiwavelength source extraction algorithm getsources. We calculated physical properties, including mass and temperature, of the GDCs from five-band Herschel PACS and SPIRE observations from 100 to 500 μm; the final size and mass estimates are based on the observations at 250 μm that have an effective spatial resolution of ~170 pc. We correlated our final catalogue of GDCs to pre-existing catalogues of HII regions to infer the number of GDCs associated with high-mass star formation and determined the Hα emission of the GDCs. Results. Our final catalogue of GDCs includes 146 sources, 90 of which are associated with known HII regions. We find that the dust masses of the GDCs are completely dominated by the cold dust component and range from ~1.1 × 103 to 1.4 × 104 M⊙. The GDCs have effective temperatures of ~13–23 K and show a distinct cold dust effective temperature gradient from the centre towards the outer parts of the stellar disk. We find that the population of GDCs in our catalogue constitutes ~16% of the total dust mass of NGC 300, which we estimate to be about 5.4 × 106 M⊙. At least about 87% of our GDCs have a high enough average dust mass surface density to provide sufficient shielding to harbour molecular clouds. We compare our results to previous pointed molecular gas observations in NGC 300 and results from other nearby galaxies and also conclude that it is very likely that most of our GDCs are associated with complexes of giant molecular clouds.

scholarly journals Dark Supernova Remnants Revealed by CO-Line Bubbles in the W43 Molecular Complex along the 4-kpc Galactic Arm

Galaxies ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 13
Author(s):  
Yoshiaki Sofue
Keyword(s):  
Molecular Clouds ◽  
Supernova Remnants ◽  
Dust Emission ◽  
Radio Continuum ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Giant Molecular Clouds ◽  
Turbulent Structures ◽  
Stellar Objects ◽  
Receiver System

Fine structure of the density distribution in giant molecular clouds (GMCs) around W43 (G31+00+90 km s−1at ∼5.5 kpc) was analyzed using the FUGIN* CO-line survey at high-angular (20”∼0.5 pc) and velocity (1.3 km s−1) resolutions (*Four-receiver-system Unbiased Galactic Imaging survey with the Nobeyama 45-m telescope). The GMCs show highly turbulent structures, and the eddies are found to exhibit spherical bubble morphology appearing in narrow ranges of velocity channels. The bubbles are dark in radio continuum emission, unlike usual supernova remnants (SNR) or HII regions, and in infrared dust emission, unlike molecular bubbles around young stellar objects. The CO bubbles are interpreted as due to fully evolved buried SNRs in molecular clouds after rapid exhaustion of the released energy in dense molecular clouds. Then, the CO bubbles may be a direct evidence for exciting and maintaining the turbulence in GMCs by SN origin. Search for CO bubbles as “dark SNRs” (dSNR) will have implication to estimate the supernova rate more accurately, and hence the star formation activity in the Milky Way.

scholarly journals Determining thermal dust emission from Planck HFI data using a sparse, parametric technique

2019 ◽  
Vol 623 ◽  
pp. A21 ◽  
Author(s):  
Melis O. Irfan ◽  
Jérôme Bobin ◽  
Marc-Antoine Miville-Deschênes ◽  
Isabelle Grenier
Keyword(s):  
Parametric Method ◽  
Dust Emission ◽  
Black Body ◽  
Point Sources ◽  
Parameter Estimates ◽  
Model Parameters ◽  
Parameter Recovery ◽  
Intensity Measurements ◽  
Full Resolution ◽  
Infrared Background

Context. The Planck data releases have provided the community with submillimetre and full-sky radio observations at unprecedented resolutions. We make use of the Planck 353, 545, and 857 GHz maps alongside the IRAS 3000 GHz map. These maps contain information on the cosmic microwave background (CMB), cosmic infrared background (CIB), extragalactic point sources, and diffuse thermal dust emission. Aims. We aim to determine the modified black-body (MBB) model parameters of thermal dust emission in total intensity and produce all-sky maps of pure thermal dust, having separated this Galactic component from the CMB and CIB. Methods. This separation is completed using a new, sparsity-based, parametric method, Parameter Recovery Exploiting Model Informed Sparse Estimates (premise). The method is comprised of three main stages: 1) filtering the raw data to reduce the effect of the CIB on the MBB fit; 2) fitting an MBB model to the filtered data across super-pixels of various sizes determined by the algorithm itself; and 3) refining these super-pixel estimates into full-resolution maps of the MBB parameters. Results. We present our maps of MBB temperature, spectral index, and optical depth at 5 arcmin resolution and compare our estimates to those of GNILC and to the two-step MBB fit presented by the Planck Collaboration in 2013. Conclusions. By exploiting sparsity we avoid the need for smoothing, enabling us to produce the first full-resolution MBB parameter maps from intensity measurements of thermal dust emission. We consider the premise parameter estimates to be competitive with the existing state-of-the-art solutions, outperforming these methods within low signal-to-noise regions as we account for the CIB without removing thermal dust emission through oversmoothing.

scholarly journals Observations of Interstellar CH at 9 cm Wavelength

1976 ◽  
Vol 29 (3) ◽  
pp. 211 ◽  
Author(s):  
FF Gardner ◽  
BJ Robinson ◽  
MW Sinclair
Keyword(s):  
Transition Temperature ◽  
Ground State ◽  
Molecular Clouds ◽  
Hii Regions ◽  
The Galaxy ◽  
Galactic Sources

The 9 cm ground-state lines of CH have been observed in southern galactic sources, mainly HII regions. The F = 0-1 transition at 3264 MHz has been detected in emission in 16 sources; the F = 1-1 transition at 3335 MHz has been seen in absorption in 5 sources and in emission in 2 others. Where the F = 1-1 transition is in absorption the transition temperature is positive and below about 100 K. The F = 0-1 transition is generally inverted, with a transition temperature between -10 and 0 K. The column densities of CH are in the vicinity of lO'4 cm-2, slightly below those for OH but many times those for H2CO. There is no correlation between apparent optical depths of CH and those for OH or H2CO absorption. There is also no enhancement of CH in the dense molecular clouds near the centre of the Galaxy.

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