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 UCHII regions in the Antennae

2006 ◽  
Vol 2 (S237) ◽  
pp. 476-476
Author(s):  
L. Snijders ◽  
L. J. Kewley ◽  
P. P. van der Werf ◽  
B. R. Brandl
Keyword(s):  
Emission Line ◽  
Spatial Resolution ◽  
Average Density ◽  
Physical Characteristics ◽  
Stellar Clusters ◽  
Mid Infrared ◽  
Infrared Observations ◽  
Star Forming ◽  
Compact Material ◽  
Star Forming Regions

AbstractWe explore the physical characteristics of young stellar clusters in the Antennae by combining recent ground- and space-based mid-infrared observations with a newly developed set of diagnostic diagrams. Spitzer data give an overview of the star-forming regions extending over hundreds of parsecs, showing a dominant diffuse ISM component with a density of 102 cm−3 plus a small fraction of very compact material (106 cm−3). With its higher spatial resolution VISIR gives a close-up view of the latter component. Its emission line ratios suggest that these regions are fundamentally different from local star-forming regions. Instead of having small isolated UCHII regions, as in local star-forming regions, the average density of the medium of the whole region falls in the (ultra)compact regime, exceeding 104 cm−3 over tens of parsecs.

scholarly journals Drama of HII regions: Clustered and Triggered Star Formation

2015 ◽  
Vol 12 (S316) ◽  
pp. 129-130
Author(s):  
Jin-Zeng Li ◽  
Jinghua Yuan ◽  
Hong-Li Liu ◽  
Yuefang Wu ◽  
Ya-Fang Huang
Keyword(s):  
Star Formation ◽  
Hii Regions ◽  
Radio Telescopes ◽  
Physical Status ◽  
Mid Infrared ◽  
Star Forming ◽  
Star Forming Regions ◽  
Dense Cores ◽  
Compressed Gas ◽  
Multi Wavelength

AbstractIn order to understand the star formation process under the influence of H ii regions, we have carried out extensive investigations to well selected star-forming regions which all have been profoundly affected by existing massive O type stars. On the basis of multi-wavelength data from mid-infrared to millimeter collected using Spitzer, Herschel, and ground based radio telescopes, the physical status of interstellar medium and star formation in these regions have been revealed. In a relatively large infrared dust bubble, active star formation is undergoing and the shell is still expanding. Signs of compressed gas and triggered star formation have been tentatively detected in a relatively small bubble. The dense cores in the Rosette Molecular Complex detected at 1.1 mm using SMA have been speculated to have a likely triggered origin according to their spatial distribution. Although some observational results have been obtained, more efforts are necessary to reach trustworthy conclusions.

scholarly journals Dust, HII and molecules towards OH and H2O masers

2002 ◽  
Vol 206 ◽  
pp. 14-17
Author(s):  
James R. Forster
Keyword(s):  
Molecular Cloud ◽  
Hii Regions ◽  
Hii Region ◽  
Star Forming ◽  
The Core ◽  
Star Forming Regions ◽  
Early Formation ◽  
Young Object ◽  
Compact Hii Regions

Radio synthesis observations made with the BIMA interferometer at 29, 86 and 216 GHz are presented for twelve galactic fields containing multiple interstellar OH and H2O maser sites. A dusty molecular cloud was found at 20 of the 23 maser sites in the fields studied. The clouds have masses in the range 50 to 800 M⊙ and diameters between 0.1 and 0.5 pc.The data show that most masers are located near the centers of massive, dusty molecular cores. The cores appear to be centrally condensed and internally excited. These results suggest that most masers found in star-forming regions are associated with a massive young object at the center of a collapsing molecular cloud. The kinematics of the core gas, and association with ultra-compact HII regions, implies that the duration of the maser phase includes collapse, expansion and early formation of an HII region.

scholarly journals Star Formation in Virgo Intracluster Space

2004 ◽  
Vol 217 ◽  
pp. 480-485
Author(s):  
Ortwin Gerhard
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Hii Regions ◽  
Virgo Cluster ◽  
Hii Region ◽  
Star Forming ◽  
Star Forming Regions ◽  
North East ◽  
Line Region ◽  
Compact Hii Regions

A number of candidate isolated compact HII regions have been discovered on combined Hα, [OIII], and broadband images in the Virgo cluster. One point-like source was spectroscopically confirmed as an HII region; this object is powered by a small starburst with an estimated mass of ~ 400 M⊙ and age of ~ 3 Myr. The object is located in the diffuse outer halo of NGC 4388, or could possibly be in intracluster space. Several resolved HII candidates are seen in the extended (~ 35 kpc) emission line region north-east of NGC 4388, perhaps triggered by the jet from the galaxy's nucleus. Star formation can thus take place far outside the main star forming regions of galaxies. The origin of the gas, the star formation, and some implications are discussed.

scholarly journals A MULTIWAVELENGTH STUDY OF YOUNG MASSIVE STAR-FORMING REGIONS. III. MID-INFRARED EMISSION

2009 ◽  
Vol 698 (1) ◽  
pp. 488-501 ◽  
Author(s):  
Esteban F. E. Morales ◽  
Diego Mardones ◽  
Guido Garay ◽  
Kate J. Brooks ◽  
Jaime E. Pineda
Keyword(s):  
Massive Star ◽  
Infrared Emission ◽  
Mid Infrared ◽  
Star Forming ◽  
Star Forming Regions

scholarly journals A radio polarimetric study to disentangle AGN activity and star formation in Seyfert galaxies

2020 ◽  
Vol 499 (1) ◽  
pp. 334-354
Author(s):  
Biny Sebastian ◽  
P Kharb ◽  
C P O’Dea ◽  
J F Gallimore ◽  
S A Baum
Keyword(s):  
Star Formation ◽  
Radio Emission ◽  
Seyfert Galaxies ◽  
Starburst Galaxies ◽  
Shock Acceleration ◽  
Very Large Array ◽  
Star Forming ◽  
Array Configuration ◽  
Star Forming Regions ◽  
Tentative Evidence

ABSTRACT To understand the origin of radio emission in radio-quiet active galactic nucleus (AGN) and differentiate between the contributions from star formation, AGN accretion, and jets, we have observed a nearby sample of Seyfert galaxies along with a comparison sample of starburst galaxies using the Expanded Very Large Array (EVLA) in full-polarization mode in the B-array configuration. The radio morphologies of the Seyfert galaxies show lobe/bubble-like features or prominent cores in radio emission, whereas the starburst galaxies show radio emission spatially coincident with the star-forming regions seen in optical images. There is tentative evidence that Seyferts tend to show more polarized structures than starburst galaxies at the resolution of our observations. We find that unlike a sample of Seyfert galaxies hosting kilo-parsec scale radio (KSR) emission, starburst galaxies with superwinds do not show radio-excess compared to the radio–FIR correlation. This suggests that shock acceleration is not adequate to explain the excess radio emission seen in Seyferts and hence most likely have a jet-related origin. We also find that the [O iii] luminosity of the Seyferts is correlated with the off-nuclear radio emission from the lobes, whereas it is not well correlated with the total emission which also includes the core. This suggests strong jet–medium interaction, which in turn limits the jet/lobe extents in Seyferts. We find that the power contribution of AGN jet, AGN accretion, and star formation is more or less comparable in our sample of Seyfert galaxies. We also find indications of episodic AGN activity in many of our Seyfert galaxies.

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.

Erratum - Optical Radio and Infrared Observations of Compact HII Regions - Part Five - the Hourglass in M8

1986 ◽  
Vol 92 ◽  
pp. 682
Author(s):  
C. E. Woodward ◽  
J. L. Pipher ◽  
H. L. Helfer ◽  
S. Sharpless ◽  
A. Moneti ◽  
...  
Keyword(s):  
Hii Regions ◽  
Infrared Observations ◽  
Compact Hii Regions

scholarly journals Searching for intergalactic star forming regions in Stephan’s Quintet with SITELLE

2019 ◽  
Vol 629 ◽  
pp. A102 ◽  
Author(s):  
S. Duarte Puertas ◽  
J. Iglesias-Páramo ◽  
J. M. Vilchez ◽  
L. Drissen ◽  
C. Kehrig ◽  
...  
Keyword(s):  
Large Scale ◽  
Dwarf Galaxy ◽  
Three Dimensional ◽  
Large Field ◽  
North West ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
The North ◽  
Spectral Ranges

Stephan’s Quintet (SQ), the prototypical compact group of galaxies in the local Universe, has been observed with the imaging Fourier transform spectrometer SITELLE, attached to the Canada-France-Hawaii-Telescope, to perform a deep search for intergalactic star-forming emission. In this paper we present the extended ionised gaseous structures detected and analyse their kinematical properties. The large field of view (11′ × 11′) and the spectral ranges of SITELLE have allowed a thorough study of the entire galaxy system, its interaction history and the main properties of the ionised gas. The observations have revealed complex three-dimensional strands in SQ seen for the first time, as well as the spatially resolved velocity field for a new SQ dwarf galaxy (M 82-like) and the detailed spectral map of NGC 7320c, confirming its AGN nature. A total of 175 SQ Hα emission regions have been found, 22 of which present line profiles with at least two kinematical components. We studied 12 zones and 28 sub-zones in the SQ system in order to define plausible physical spatial connections between its different parts in the light of the kinematical information gathered. In this respect we have found five velocity systems in SQ: (i) v = [5600−5900] km s−1 associated with the new intruder and the southern debris region; (ii) v = [5900−6100] km s−1, associated with the north starburst A and south starburst A and the strands connected to these zones; (iii) v = [6100−6600] km s−1, associated with the strands from the large-scale shock region (LSSR); (iv) v = [6600−6800] km s−1, associated with the young tidal tail, the starburst A (SQA), NGC 7319, and the NGC 7319 north lobe; and (v) v = [6800−7000] km s−1, associated with the strands seen connecting LSSR with SQA. We fail to detect ionised gas emission in the old tail, neither in the vicinity of NGC 7318A nor in NGC 7317, and the connection between NGC 7319 north lobe and SQA cannot be confirmed. Conversely, a clear gaseous bridge has been confirmed both spatially and kinematically between the LSSR zone and the NGC 7319 AGN nucleus. Finally, a larger scale, outer rim winding the NGC 7318B/A system clockwise north-west to south-east has been highlighted in continuum and in Hα. This structure may be reminiscent of a sequence of a previously proposed scenario for SQ a sequence of individual interactions.

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