- ID:
- ivo://CDS.VizieR/J/A+A/579/A71
- Title:
- Infrared emission of young HII regions
- Short Name:
- J/A+A/579/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Investigating the relationship between radio and infrared emission of HII regions may help shed light on the nature of the ionizing stars and the formation mechanism of early-type stars in general. We have taken advantage of recent unbiased surveys of the Galactic plane such as Herschel/Hi-GAL and VLA/CORNISH to study a bona fide sample of young HII regions located in the Galactic longitude range 10{deg}-65{deg} by comparing the mid- and far-IR continuum emission to the radio free-free emission at 5GHz. We have identified the Hi-GAL counterparts of 230 CORNISH HII regions and reconstructed the spectral energy distributions of 204 of these by complementing the Hi-GAL fluxes with ancillary data at longer and shorter wavelengths. Using literature data, we obtained a kinematical distance estimate for 200 HII regions with Hi-GAL counterparts and determined their luminosities by integrating the emission of the corresponding spectral energy distributions. We have also estimated the mass of the associated molecular clumps from the (sub)millimeter flux densities. Our main finding is that for ~1/3 of the HII regions the Lyman continuum luminosity appears to be greater than the value expected for a zero-age main-sequence star with the same bolometric luminosity. This result indicates that a considerable fraction of young, embedded early-type stars presents a "Lyman excess" possibly due to UV photons emitted from shocked material infalling onto the star itself and/or a circumstellar disk. Finally, by comparing the bolometric and Lyman continuum luminosities with the mass of the associated clump, we derive a star formation efficiency of 5%. The results obtained suggest that accretion may still be present during the early stages of the evolution of HII regions, with important effects on the production of ionizing photons and thus on the circumstellar environment. More reliable numerical models describing the accretion process onto massive stars are required to shed light on the origin of the observed Lyman excess.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/537/A1
- Title:
- Infrared fluxes of HII regions and PNe
- Short Name:
- J/A+A/537/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine infrared color criteria for distinguishing between HII regions and planetary nebulae.
- ID:
- ivo://CDS.VizieR/J/AJ/161/206
- Title:
- Infrared imaging of new born cluster H72.97-69.39
- Short Name:
- J/AJ/161/206
- Date:
- 20 Jan 2022
- Publisher:
- CDS
- Description:
- Young massive clusters and super star clusters (SSCs) represent an extreme mode of star formation. Far-infrared imaging of the Magellanic Clouds has identified one potential embedded SSC, HSO-BMHERICC-J72.971176-69.391112 (H72.97-69.39 in short), in the southwest outskirts of the Large Magellanic Cloud. We present Gemini Flamingos 2 and GSAOI near-infrared imaging of a 3'x3' region around H72.97-69.39 in order to characterize the stellar content of the cluster. The stellar content is probed down to 1.5M{sun}. We find substantial dust extinction across the cluster region, extending up to A_K_ of 3. Deeply embedded stars are associated with ALMA-detected molecular gas suggesting that star formation is ongoing. The high spatial resolution of the GSAOI data allows identification of the central massive object associated with the ^13^CO ALMA observations and detection of fainter low-mass stars around the H30{alpha} ALMA source. The morphology of the molecular gas and the nebulosity from adjacent star formation suggest they have interacted covering a region of several parsecs. The total stellar content in the cluster is estimated from the intermediate and high-mass stellar content to be at least 10000M{sun}, less than R136 with up to 100000M{sun} within 4.7pc radius, but places it in the regime of an SSC. Based on the extinction determination of individual stars we estimate a molecular gas mass in the vicinity of H72.97-69.39 of 6600M{sun}, suggesting more star formation can be expected.
- ID:
- ivo://CDS.VizieR/J/PAZh/31/332
- Title:
- Infrared Luminosities of Local Galaxies
- Short Name:
- J/PAZh/31/332
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on data from 2MASS (<II/246>) we analyzed the infrared properties of 451 Local-Volume galaxies at distances D<=10Mpc.
- ID:
- ivo://CDS.VizieR/J/A+A/528/A35
- Title:
- Infrared luminosity in GOODS fields
- Short Name:
- J/A+A/528/A35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the evolution of the infrared luminosity function (LF) over the last 4/5ths of cosmic time using deep 24um and 70um imaging of the GOODS North and South fields. We perform a stacking analysis to characterize the observed L_24_/(1+z) vs L_70_/(1+z) correlation. Then, using spectral energy distribution templates which best fit this correlation, we derive the infrared luminosity of individual sources from their 24um and 70um luminosities. We then compute the infrared LF at z=1.55+/-0.25 and z=2.05+/-0.25. The redshift evolution of the infrared LF from z=1.5 to z=2 is consistent with a luminosity evolution proportional to (1+z)^1.0+/-0.9^ combined with a density evolution proportional to (1+z)^-1.1+/-1.5^. At z=2, LIRGs are still the main contributors, at 49%, to the total comoving infrared luminosity density of the Universe while ULIRGs account for 17%.
- ID:
- ivo://CDS.VizieR/J/AJ/104/1349
- Title:
- Infrared-luminous giants in M32
- Short Name:
- J/AJ/104/1349
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A previously unknown population of very luminous, red, asymptotic-giant-branch stars has been identified as a result of near-infrared (JHK) imaging in the dwarf elliptical galaxy M32. Situated above the tip of the normal first red giant branch, these stars are intrinsically brighter than the most luminous normal giants in old Galactic globular clusters by approximately 2 bolometric magnitudes. Moreover, they are a full bolometric magnitude brighter than the brightest giants observed in our own Galactic bulge. Several possible explanations for this population are examined, including old long-period variables, binary mergers, supermetallicity, and intermediate-age stars. It is suggested that the simplest explanation at present, is that M32 had a star formation episode less than about 5 billion years ago. These stars would then be the evolved extended asymptotic giant branch population resulting from that event (similar to those stars observed in the intermediate-age clusters in the Magellanic Clouds). This population may be similar to that in the M31 bulge, recently observed by Rich and Mould. The detection of a young component in M32 is of particular interest because historically, M32 has been a fiducial galaxy for population synthesis techniques. An understanding of M32 remains crucial for our understanding of distant and more luminous elliptical galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A100
- Title:
- Infrared massive stellar content of M83
- Short Name:
- J/A+A/578/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of point sources in the field of M83. Sources were first cataloged that were found in both Spitzer IRAC 3.6-micron and 4.5-micron images. These were then supplemented with 5.8 and 8.0-micron photometry. Ground-based near-IR photometry in J and Ks-bands were extracted from imaging from the FourStar camera on the Baade Magellan Telescope at Las Campanas Observatory. Optical photometry was extracted from Hubble Space Telescope Wide Field Camera 3 observations of seven fields covering much of the bright disk region of M83.
- ID:
- ivo://CDS.VizieR/J/AJ/133/1528
- Title:
- Infrared nebulae around young stellar objects
- Short Name:
- J/AJ/133/1528
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a K-band atlas of 106 reflection nebulae, 41 of which are new discoveries. We observed these nebulae with the University of Hawaii 2.2m telescope in the course of an imaging survey of 197 objects that were selected as nearby young Class I sources. K-band images and flux-calibrated surface brightness contour plots of each nebula are presented.
- ID:
- ivo://CDS.VizieR/J/other/NewA/44.1
- Title:
- Infrared photometric study of Herbig Ae/Be stars
- Short Name:
- J/other/NewA/44.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we collected almost all HAeBe stars known so far (253 sources in total) to photometrically study their infrared properties. The 2MASS, WISE, IRAS and AKARI data are employed to make analyses. It is shown from several two-color diagrams that from 1um to 60um infrared radiations from circumstellar disks with the power law distribution play a very important role for infrared excesses which are much larger than that for ordinary Be stars. In the WISE two-color diagram, (W2-W3) vs. (W1-W2), some sources show thermal emissions probably due to dust surrounded and enhanced PAH features at 3.3 and 11.3um. In the wavelength longer than 60um infrared radiations are not so influenced by the circumstellar disk, but mainly from the ISM surrounded.
- ID:
- ivo://CDS.VizieR/J/AJ/155/17
- Title:
- Infrared photometric study of Wolf-Rayet galaxies
- Short Name:
- J/AJ/155/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We collected observational data on 781 Wolf-Rayet (WR) galaxies from the literature to photometrically study their infrared properties measured by the 2MASS, WISE, IRAS, AKARI, and Herschel missions. It is found that in the 1-5 {mu}m range the radiations of WR galaxies are dominated by the free-free emissions from the stellar winds and the circumstellar dust from the late-type stars in the host galaxy. In the 5-22 {mu}m range, the radiation of WR galaxies is dominated by the free-free emissions and the synchrotron radiation from the central active galactic nucleus (AGN; but not always present). In the 22-140 {mu}m range, the radiations of WR galaxies are dominated by the free-free emissions and the star formation/starburst activities. In the 250-500 {mu}m range, the radiation of WR galaxies is dominated by the free-free emissions. In addition, the comparison with the non-WR galaxies is made. It is shown that some star formation WR galaxies have redder near-infrared colors than non-WR star-forming galaxies probably due to the gas emission in the near-infrared. In the 2-5 {mu}m region WR galaxies have redder colors due to the thermal emission from circumstellar dust of late-type stars and the enhanced gas emission. In the 5-22 {mu}m region, both WR galaxies and non-WR galaxies have similar behavior, indicative of having similar free-free emission as the dominant radiation. In the 25-140 {mu}m region, both types of galaxies also have similar behavior, indicative of having free-free emission from the stellar winds or the thermal radiation from the starburst/star formation as the dominant radiation.
