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 Constraining How Star Formation Proceeds: Surveys in the Sub-mm and FIR

2009 ◽  
Vol 5 (H15) ◽  
pp. 406-407
Author(s):  
Doug Johnstone
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Mass Star ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Dense Cores ◽  
Multi Wavelength ◽  
Low Mass ◽  
High Column

AbstractCoordinated multi-wavelength surveys of molecular clouds are providing strong constraints on the physical conditions within low-mass star-forming regions. In this manner, Perseus and Ophiuchus have been exceptional laboratories for testing the earliest phases of star formation. Highlights of these results are: (1) dense cores form only in high column density regions, (2) dense cores contain only a few percent of the cloud mass, (3) the mass distribution of the dense cores is similar to the IMF, (4) the more massive cores are most likely to contain embedded protostars, and (5) the kinematics of the dense cores and the bulk gas show significant coupling.

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 ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – I. Survey description and a first look at G9.62+0.19

2020 ◽  
Vol 496 (3) ◽  
pp. 2790-2820 ◽  
Author(s):  
Tie Liu ◽  
Neal J Evans ◽  
Kee-Tae Kim ◽  
Paul F Goldsmith ◽  
Sheng-Yuan Liu ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Star Formation ◽  
Survey Data ◽  
Massive Star ◽  
High Mass ◽  
Dense Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Stellar Feedback ◽  
Dense Cores

ABSTRACT The ATOMS, standing for ALMA Three-millimeter Observations of Massive Star-forming regions, survey has observed 146 active star-forming regions with ALMA band 3, aiming to systematically investigate the spatial distribution of various dense gas tracers in a large sample of Galactic massive clumps, to study the roles of stellar feedback in star formation, and to characterize filamentary structures inside massive clumps. In this work, the observations, data analysis, and example science of the ATOMS survey are presented, using a case study for the G9.62+0.19 complex. Toward this source, some transitions, commonly assumed to trace dense gas, including CS J = 2−1, HCO+J = 1−0, and HCN J = 1−0, are found to show extended gas emission in low-density regions within the clump; less than 25 per cent of their emission is from dense cores. SO, CH3OH, H13CN, and HC3N show similar morphologies in their spatial distributions and reveal well the dense cores. Widespread narrow SiO emission is present (over ∼1 pc), which may be caused by slow shocks from large–scale colliding flows or H ii regions. Stellar feedback from an expanding H ii region has greatly reshaped the natal clump, significantly changed the spatial distribution of gas, and may also account for the sequential high-mass star formation in the G9.62+0.19 complex. The ATOMS survey data can be jointly analysed with other survey data, e.g. MALT90, Orion B, EMPIRE, ALMA_IMF, and ALMAGAL, to deepen our understandings of ‘dense gas’ star formation scaling relations and massive protocluster formation.

scholarly journals Star formation on galactic scales

2006 ◽  
Vol 2 (S237) ◽  
pp. 311-316
Author(s):  
Robert C. Kennicutt
Keyword(s):  
Star Formation ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
Multi Wavelength ◽  
Nearby Galaxies

AbstractNew multi-wavelength data on nearby galaxies are providing a much more accurate and complete observational picture of star formation on galactic scales. Here I briefly report on recent results from the Spitzer Infrared Nearby Galaxies Survey (SINGS). These provide new constraints on the frequency and lifetime of deeply obscured star-forming regions in galaxies, the measurement of dust-corrected star formation rates in galaxies, and the form of the spatially-resolved Schmidt law.

scholarly journals Continuous Mid-Infrared Star Formation Rate Indicators

2014 ◽  
Vol 10 (S309) ◽  
pp. 167-168
Author(s):  
A. J. Battisti ◽  
D. Calzetti ◽  
B. D. Johnson ◽  
D. Elbaz
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Flexible Tool ◽  
Mid Infrared ◽  
Infrared Wavelength ◽  
Star Forming ◽  
James Webb Space Telescope ◽  
Multi Wavelength ◽  
Infrared Star

AbstractWe present continuous, monochromatic star formation rate (SFR) indicators over the mid-infrared wavelength range of 6–70 μm. We use a sample of 58 star forming galaxies (SFGs) in the Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS) at z<0.2, for which there is a rich suite of multi-wavelength photometry and spectroscopy from the ultraviolet through to the infrared. The data from the Spitzer infrared spectrograph (IRS) of these galaxies, which spans 5–40 μm, is anchored to their photometric counterparts. The spectral region between 40-70 μm is interpolated using dust model fits to the IRS spectrum anchored by Spitzer 70 and 160 μm photometry. Since there are no sharp spectral features in this region, we expect these interpolations to be robust. This spectral range is calibrated as a SFR diagnostic using several reference SFR indicators to mitigate potential bias. Our band-specific continuous SFR indicators are found to be consistent with monochromatic calibrations in the local universe, as derived from Spitzer, WISE, and Herschel photometry. Additionally, in the era of the James Webb Space Telescope this will become a flexible tool, applicable to any SFG up to z∼3.

scholarly journals Probing Individual Star Forming Regions Within Strongly Lensed Galaxies at z > 1

2014 ◽  
Vol 10 (S309) ◽  
pp. 251-254
Author(s):  
Matthew B. Bayliss ◽  
Jane R. Rigby ◽  
Keren Sharon ◽  
Michael D. Gladders ◽  
Eva Wuyts
Keyword(s):  
Star Formation ◽  
Gravitational Lensing ◽  
Velocity Structure ◽  
Spectroscopic Studies ◽  
Uv Spectra ◽  
Star Forming ◽  
Star Forming Regions ◽  
Wide Range ◽  
Individual Star ◽  
Multi Wavelength

AbstractStar formation occurs on physical scales corresponding to individual star forming regions, typically of order ∼100 parsecs in size, but current observational facilities cannot resolve these scales within field galaxies beyond the local universe. However, the magnification from strong gravitational lensing allows us to measure the properties of these discrete star forming regions within galaxies in the distant universe. New results from multi-wavelength spectroscopic studies of a sample of extremely bright, highly magnified lensed galaxies are revealing the complexity of star formation on sub-galaxy scales during the era of peak star formation in the universe. We find a wide range of properties in the rest-frame UV spectra of individual galaxies, as well as in spectra that originate from different star forming regions within the same galaxy. Large variations in the strengths and velocity structure of Lyman-alpha and strong P Cygni lines such as C IV, and MgII provide new insights into the astrophysical relationships between extremely massive stars, the elemental abundances and physical properties of the nebular gas those stars ionize, and the galactic-scale outflows they power.

scholarly journals Star formation activity and the spatial distribution and mass segregation of dense cores in the early phases of star formation

2019 ◽  
Vol 629 ◽  
pp. A135 ◽  
Author(s):  
Sami Dib ◽  
Thomas Henning
Keyword(s):  
Spatial Distribution ◽  
Star Formation ◽  
Large Scale ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Dense Cores ◽  
Star Formation Activity ◽  
Mass Segregation ◽  
Massive Cores

We examine the spatial distribution and mass segregation of dense molecular cloud cores in a number of nearby star forming regions (the region L1495 in Taurus, Aquila, Corona Australis, and W43) that span about four orders of magnitude in star formation activity. We used an approach based on the calculation of the minimum spanning tree, and for each region, we calculated the structure parameter 𝒬 and the mass segregation ratio ΛMSR measured for various numbers of the most massive cores. Our results indicate that the distribution of dense cores in young star forming regions is very substructured and that it is very likely that this substructure will be imprinted onto the nascent clusters that will emerge out of these clouds. With the exception of Taurus in which there is nearly no mass segregation, we observe mild-to-significant levels of mass segregation for the ensemble of the 6, 10, and 14 most massive cores in Aquila, Corona Australis, and W43, respectively. Our results suggest that the clouds’ star formation activity are linked to their structure, as traced by their population of dense cores. We also find that the fraction of massive cores that are the most mass segregated in each region correlates with the surface density of star formation in the clouds. The Taurus region with low star forming activity is associated with a highly hierarchical spatial distribution of the cores (low 𝒬 value) and the cores show no sign of being mass segregated. On the other extreme, the mini-starburst region W43-MM1 has a higher 𝒬 that is suggestive of a more centrally condensed structure. Additionally, it possesses a higher fraction of massive cores that are segregated by mass. While some limited evolutionary effects might be present, we largely attribute the correlation between the star formation activity of the clouds and their structure to a dependence on the physical conditions that have been imprinted on them by the large scale environment at the time they started to assemble.

scholarly journals Low-Mass Versus High-Mass Star Formation

1997 ◽  
Vol 182 ◽  
pp. 537-549
Author(s):  
T. W. Hartquist ◽  
J. E. Dyson
Keyword(s):  
Star Formation ◽  
Young Stars ◽  
High Mass ◽  
Mass Star ◽  
Low Mass Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Dense Cores ◽  
Global Properties ◽  
Low Mass

Structures like the clumps identified in the CO maps of the Rosette Molecular Cloud and the dense cores such as those in B5, a cluster of cores and young low-mass stars, are key to considerations of star formation. Whether star formation is a self-inducing process or one that causes itself to turn off depends greatly on whether the responses of the interclump and intercore media to young stars cause the collapse of clumps or cores to be faster than their ablation. We present a naive introduction to the lengthscales over which such responses are significant, mention ways in which the responses might induce collapse, review some of the little that is known of how flows of media around clumps and cores ablate them, and then return to the issue of the lengthscales over which such responses are significant by considering the global properties of mass-loaded flows in clumpy star forming regions.

scholarly journals Galaxy evolution and radiative properties in the early universe: Multi-wavelength analysis in cosmological simulations

2019 ◽  
Vol 15 (S352) ◽  
pp. 55-59
Author(s):  
Shohei Arata ◽  
Hidenobu Yajima ◽  
Kentaro Nagamine ◽  
Yuexing Li ◽  
Sadegh Khochfar
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Radiative Properties ◽  
Star Formation History ◽  
Star Forming ◽  
Bolometric Luminosity ◽  
Star Forming Regions ◽  
Neutral Gas ◽  
Multi Wavelength ◽  
First Galaxies

AbstractRecent observations have successfully detected UV or infrared flux from galaxies at the epoch of reionization. However, the origin of their radiative properties has not been fully understood yet. Combining cosmological hydrodynamic simulations and radiative transfer calculations, we present theoretical predictions of multi-wavelength radiative properties of the first galaxies at z = 6–15. We find that most of the gas and dust are ejected from star-forming regions due to supernova (SN) feedback, which allows UV photons to escape. We show that the peak of SED rapidly shifts between UV and infrared wavelengths on a timescale of 100 Myr due to intermittent star formation and feedback. When dusty gas covers the star-forming regions, the galaxies become bright in the observed-frame sub-millimeter wavelengths. In addition, we find that the escape fraction of ionizing photons also changes between 1–40% at z > 10. The mass fraction of H ii region changes with star formation history, resulting in fluctuations of metal lines and Lyman-α line luminosities. In the starbursting phase of galaxies with a halo mass ∼1011Mȯ (1012Mȯ), the simulated galaxy has L[OIII] ∼ 1042 (1043) erg s−1, which is consistent with the observed star-forming galaxies at z > 7. Our simulations suggest that deep [Cii] observation with ALMA can trace the distribution of neutral gas extending over ∼20 physical kpc. We also find that the luminosity ratio L[OIII]/L[CII] decreases with bolometric luminosity due to metal enrichment. Our simulations show that the combination of multi-wavelength observations by ALMA and JWST will be able to reveal the multi-phase ISM structure and the transition from starbursting to outflowing phases of high-z galaxies.

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.

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