scholarly journals A Study of Low density Ionized Gas in the Galactic Plane

2002 ◽  
Vol 199 ◽  
pp. 335-338
Author(s):  
D. Anish Roshi ◽  
K. R. Anantharamaiah
Keyword(s):  
Radio Telescope ◽  
Radial Distribution ◽  
Angular Resolution ◽  
Galactic Plane ◽  
Hii Regions ◽  
Low Density ◽  
Ionized Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Complete Survey

A complete survey of radio recombination lines (RRLs) near 327 MHz from the galactic plane (l = 330° − 0°-89°, b = 0°) was carried out using a section of the Ooty Radio Telescope (ORT) with an angular resolution of 2° × 2°. A subset of regions in the same area was observed using the whole telescope which has a beam of 2° × 6'. Hydrogen RRLs were detected in most of the positions that were observed. The lv diagram and radial distribution computed from the observed spectra and their comparison with other species in the galactic plane indicate that the low density gas detected in the survey is distributed similar to the star forming regions. For an assumed temperature of 7000 K, we estimate that the densities and sizes of the regions are in the range 1 — 10 cm−3 and 20 — 200 pc respectively. Our data suggests that the low density ionized gas is in the form of outer envelopes of normal HII regions.

scholarly journals First Results from ATCA at Millimetre Wavelengths

2004 ◽  
Vol 221 ◽  
pp. 275-282
Author(s):  
Vincent Minier
Keyword(s):  
Star Formation ◽  
Angular Resolution ◽  
Galactic Plane ◽  
Dust Emission ◽  
Protoplanetary Disks ◽  
High Angular Resolution ◽  
Star Forming ◽  
Star Forming Regions ◽  
First Results ◽  
Excellent Tool

The newly upgraded Australia Telescope Compact Array (ATCA) at millimetre wavelengths is the first millimetre interferometer to be built in the Southern Hemisphere. The full array will be operational in 2004-2005 and will provide arcsec angular resolution at 3 mm and 12 mm. This will be a unique instrument to study at high angular resolution the interstellar chemistry and more generally the star formation process, especially in the bulk of the galactic plane and in the Magellanic Clouds. The upgraded ATCA will also be an excellent tool to detect dust emission from nearby protoplanetary disks. In this paper I will present the first results from the upgraded ATCA at 3 mm and 12 mm. The result review will cover the topics of massive star formation and hot molecular cores dust emission from star-forming regions and detection of protoplanetary disks.

scholarly journals The Youngest Star-Forming Regions in Galaxies: Giant Compact HII Regions and Protoglobular Clusters?

2001 ◽  
Vol 205 ◽  
pp. 224-227
Author(s):  
Jean L. Turner
Keyword(s):  
Dwarf Galaxy ◽  
Hii Regions ◽  
Starburst Galaxies ◽  
Mid Infrared ◽  
Infrared Observations ◽  
Star Forming ◽  
Bolometric Luminosity ◽  
Star Forming Regions ◽  
Young Clusters ◽  
Compact Hii Regions

Subarcsecond radio and infrared observations reveal a class of luminous, obscured, optically thick HII regions associated with extremely large young clusters in nearby starburst galaxies. VLA images show bright radio nebulae with ne ∼ 104 cm−3, densities characteristic of young Galactic compact HII regions. Excitation of the nebulae requires the presence of several thousand O stars within regions of 1-10 pc extent, corresponding to clusters containing 105–106 stars. The compact nebulae are also bright in the mid-infrared, and can for significant fractions of not only the total IR luminosity, but also the total bolometric luminosity, of the parent galaxies. The prototype for these “supernebulae” is the large, obscured cluster in the dwarf galaxy NGC 5253.

scholarly journals Masers as probes of proto-planetary discs

2004 ◽  
Vol 202 ◽  
pp. 362-364
Author(s):  
A.M.S. Richards ◽  
R. J. Cohen ◽  
M. Crocker ◽  
E. E. Lekht ◽  
V. Samodourov ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Radio Telescope ◽  
Keplerian Orbit ◽  
Proper Motions ◽  
Central Mass ◽  
Maser Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
Velocity Variations ◽  
Water Maser

Water maser emission from star forming regions has been monitored for several decades using the Puschino radio telescope, showing radial velocity variations consistent with material in Keplerian orbit around protostars. MERLIN and the EVN are now being used to image the 22 GHz emission on au scales and measure proper motions. This will distinguish discs from outflows, and provide an estimate of the central mass and possibly orbiting condensations.

scholarly journals Radio Recombination Lines from Starburst Galaxies: High and Low Density Ionized Gas

2002 ◽  
Vol 199 ◽  
pp. 243-244
Author(s):  
N.R. Mohan ◽  
K.R. Anantharamaiah ◽  
W.M. Goss
Keyword(s):  
Flux Density ◽  
Hii Regions ◽  
Starburst Galaxies ◽  
High Density ◽  
The Other ◽  
Low Density ◽  
Ionized Gas ◽  
Density Measurements ◽  
Radio Recombination Lines ◽  
Upper Limits

Radio recombination lines (RRL) at 8 GHz and 15 GHz detected from four starburst galaxies are shown to arise in compact high density HII regions, which are undetectable below ∼4 GHz. Detection of an RRL at 1.4 GHz towards one galaxy and upper limits in the other three are consistent with the presence of an equal amount of low density diffuse gas. Continuum flux density measurements using the GMRT will be important in constraining the properties of the diffuse gas.

scholarly journals IONIZED GAS TOWARD MOLECULAR CLUMPS: PHYSICAL PROPERTIES OF MASSIVE STAR-FORMING REGIONS

2009 ◽  
Vol 707 (1) ◽  
pp. 283-309 ◽  
Author(s):  
Katharine G. Johnston ◽  
Debra S. Shepherd ◽  
James E. Aguirre ◽  
Miranda K. Dunham ◽  
Erik Rosolowsky ◽  
...  
Keyword(s):  
Physical Properties ◽  
Massive Star ◽  
Ionized Gas ◽  
Star Forming ◽  
Star Forming Regions

Sardinia Radio Telescope (SRT) observations of Local Group dwarf galaxies

2017 ◽  
Vol 13 (S336) ◽  
pp. 109-112
Author(s):  
A. Tarchi ◽  
P. Castangia ◽  
G. Surcis ◽  
A. Brunthaler ◽  
K. M. Menten ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Radio Continuum ◽  
Maser Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
First Results ◽  
Ngc 6822 ◽  
Almost All

AbstractThe dwarf galaxies in the Local Group (LG) reveal a surprising amount of spatial structuring. In particular, almost all non-satellite dwarfs belong to one of two planes that show a very pronounced symmetry. In order to determine if these structures in the LG are dynamically stable or, alternatively, if they only represent transient alignments, proper motion measurements of these galaxies are required. A viable method to derive proper motions is offered by VLBI studies of 22-GHz water (and 6.7-GHz methanol) maser lines in star-forming regions.In 2016, in the framework of the Early Science Program of the Sardinia Radio Telescope (SRT), we have conducted an extensive observational campaign to map the entire optical body of all the LG dwarf galaxies that belong to the two planes, at C and K band, in a search for methanol and water maser emission.Here, we outline the project and present its first results on 3 targets, NGC 6822, IC 1613, and WLM. While no luminous maser emission has been detected in these galaxies, a number of interesting weaker detections has been obtained, associated with particularly active star forming regions. In addition, we have produced deep radio continuum maps for these galaxies, aimed at investigating their star forming activity and providing an improved assessment of star formation rates in these galaxies.

scholarly journals NGC 7469 as seen by MEGARA: new results from high-resolution IFU spectroscopy

2020 ◽  
Vol 493 (3) ◽  
pp. 3656-3675 ◽  
Author(s):  
S Cazzoli ◽  
A Gil de Paz ◽  
I Márquez ◽  
J Masegosa ◽  
J Iglesias ◽  
...  
Keyword(s):  
High Resolution ◽  
Spatial Scales ◽  
High Signal ◽  
Ionized Gas ◽  
Narrow Component ◽  
Star Forming ◽  
Star Forming Regions ◽  
Solar Metallicity ◽  
Field Unit ◽  
Ngc 7469

ABSTRACT We present our analysis of high-resolution (R ∼ 20 000) GTC/MEGARA integral-field unit spectroscopic observations, obtained during the commissioning run, in the inner region (12.5 arcsec × 11.3 arcsec) of the active galaxy NGC 7469, at spatial scales of 0.62 arcsec. We explore the kinematics, dynamics, ionization mechanisms, and oxygen abundances of the ionized gas, by modelling the H α-[N ii] emission lines at high signal-to-noise (> 15) with multiple Gaussian components. MEGARA observations reveal, for the first time for NGC 7469, the presence of a very thin (20 pc) ionized gas disc supported by rotation (V/σ = 4.3), embedded in a thicker (222 pc), dynamically hotter (V/σ  =  1.3) one. These discs nearly corotate with similar peak-to-peak velocities (163  versus  137 km s−1), but with different average velocity dispersion (38 ± 1 versus 108 ± 4 km s−1). The kinematics of both discs could be possibly perturbed by star-forming regions. We interpret the morphology and the kinematics of a third (broader) component (σ > 250 km s−1) as suggestive of the presence of non-rotational turbulent motions possibly associated either to an outflow or to the lense. For the narrow component, the [N ii]/H α ratios point to the star-formation as the dominant mechanism of ionization, being consistent with ionization from shocks in the case of the intermediate component. All components have roughly solar metallicity. In the nuclear region of NGC 7469, at r ≤ 1.85 arcsec, a very broad (FWHM  =  2590 km s−1) H α component is contributing (41 per cent) to the global H α-[N ii] profile, being originated in the (unresolved) broad line region of the Seyfert 1.5 nucleus of NGC 7469.

scholarly journals A multifrequency study of the active star forming region NGC 6357

2006 ◽  
Vol 2 (S237) ◽  
pp. 400-400
Author(s):  
C. E. Cappa ◽  
R. H. Barbá ◽  
M. Arnal ◽  
N. Duronea ◽  
E. Fernández Lajús ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Massive Stars ◽  
Radio Continuum ◽  
Large Array ◽  
Schmidt Telescope ◽  
Ionized Gas ◽  
Very Large Array ◽  
Active Star ◽  
Star Forming ◽  
Spiral Arm

To investigate the interaction of the massive stars with the gas and dust in the active star forming region NGC 6357, located in the Sagittarius spiral arm at a distance of 1.7-2.6 kpc (Massey et al. 2001), we analyzed the distribution of the neutral and ionized gas, and that of the dust, based on Hα, [OIII] and [SII] images obtained with the Curtis-Schmidt telescope at CTIO, radio continuum observations at 1.465 MHz obtained with the Very Large Array (NRAO) in the DnC configuration (synthesized beam = 38″), Hi data from the Parkes survey (angular resolution = 15′), CO(1-0) observations obtained with the Nanten radiotelescope at Las Campanas Observatory (angular resolution = 2.7′), and IR images in the four MSX bands (angular resolution = 18.3″).

scholarly journals Ammonia towards dust clumps in the giant molecular cloud associated with RCW 106

2012 ◽  
Vol 8 (S292) ◽  
pp. 50-50
Author(s):  
Vicki Lowe ◽  
Maria R. Cunningham ◽  
James S. Urquhart ◽  
Shinji Horiuchi
Keyword(s):  
Star Formation ◽  
Radio Telescope ◽  
Molecular Cloud ◽  
Galactic Plane ◽  
High Mass ◽  
Mass Star ◽  
Giant Molecular Clouds ◽  
Molecular Line ◽  
Star Forming ◽  
Star Formation Regions

AbstractHigh-mass stars are known to be born within giant molecular clouds (GMCs); However, the exact processes involved in forming a high-mass star are still not well understood. It is clear that high-mass stars do not form in isolation, and that the processes surrounding high-mass star formation may affect the environment of the entire molecular cloud. We are studying the GMC associated with RCW 106 (G333), which is one of the most active massive-star formation regions in the Galactic plane. This GMC, located at l = 333° b = − 0.5°, has been mapped in over 20 molecular line transitions with the Mopra radio telescope (83-110 GHz), in Australia, and with the Swedish-ESO Submillimeter Telescope (SEST) in the 1.2 mm cool dust continuum. The region is also within the Spitzer GLIMPSE infrared survey (3.6, 4.5, 5.8, and 8.0 μm) area. We have decomposed the dust continuum using a clump-finding algorithm (CLUMPFIND), and are using the multiple molecular line traditions from the Mopra radio telescope to classify the type and stage of star formation taking place therein. Having accurate physical temperatures of the star forming clumps is essential to constrain other parameters to within useful limits. To achieve this, we have obtained pointed NH3 observations from the Tidbinbilla 70-m radio telescope, in Australia, towards these clumps.

scholarly journals Image Digitisation of Outflows and the AAO/UKST Hα Survey

1998 ◽  
Vol 15 (1) ◽  
pp. 165-166
Author(s):  
W. J. Zealey ◽  
S. L. Mader
Keyword(s):  
High Resolution ◽  
Emission Line ◽  
Galactic Plane ◽  
Star Forming ◽  
Star Forming Regions ◽  
Sky Survey ◽  
High Resolution Images ◽  
Line Survey

AbstractThe Hα emission-line survey of the Southern Sky to be carried out by the AAO/UKST will provide deep, high resolution images of Galactic Plane sources allowing the detection of new and existing filamentary sources such as Herbig–Haro objects. Used in conjunction with the existing ESO/SERC Southern Sky Survey Plates, the Hα plates will provide us with the opportunity to study the morphology and environment of new and existing star forming regions.

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