- ID:
- ivo://CDS.VizieR/J/ApJ/517/282
- Title:
- Atomic carbon observations of H II regions
- Short Name:
- J/ApJ/517/282
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report observations of atomic carbon (C I [^3^P - ^3^P_0_]) for a sample of 49 southern hemisphere H II regions using the Antarctic Submillimeter Telescope and Remote Observatory. The sources are compact and isolated members of the Wilson et al. (1970) H109{alpha} radio recombination line (RRL) catalog. The fourth Galactic quadrant is well covered by the sample. Atomic carbon emission is detected toward all of the regions, with multiple C I emission components found toward most sources. The RRL velocity is used to identify the C I emission associated with the H II region. We measure the mean velocity difference between the C I and RRL emission to be 0.8{+/-}2.8 km s^-1^. Within the measurement errors this is exact agreement in velocity; we conclude that all H II regions have associated C I emission. The mean C I line temperature of these components is 2.4{+/-}1.8 K, compared with 0.7{+/-}0.7 K for the C I emission components not associated with the H II region. This suggests that C I intensity is dominated by local heating. The FWHM line width of C I gas associated with H II regions also is marginally greater than that found for unassociated gas (6.7{+/-}3.0, compared with 4.8{+/-}2.4 km s-1).
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/835/55
- Title:
- AzTEC/ASTE survey at 1.1mm toward the SMC
- Short Name:
- J/ApJ/835/55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first 1.1mm continuum survey toward the Small Magellanic Cloud (SMC) was performed using the AzTEC instrument installed on the ASTE 10m telescope. This survey covered 4.5deg^2^ of the SMC with 1{sigma} noise levels of 5-12mJy/beam, and 44 extended objects were identified. The 1.1mm extended emission has good spatial correlation with Herschel 160{mu}m, indicating that the origin of the 1.1mm extended emission is thermal emission from a cold dust component. We estimated physical properties using the 1.1mm and filtered Herschel data (100, 160, 250, 350, and 500{mu}m). The 1.1mm objects show dust temperatures of 17-45K and gas masses of 4x10^3^-3x10^5^M_{sun}_, assuming single-temperature thermal emission from the cold dust with an emissivity index, {beta}, of 1.2 and a gas-to-dust ratio of 1000. These physical properties are very similar to those of giant molecular clouds (GMCs) in our galaxy and the Large Magellanic Cloud. The 1.1mm objects also displayed good spatial correlation with the Spitzer 24{mu}m and CO emission, suggesting that the 1.1mm objects trace the dense gas regions as sites of massive star formation. The dust temperature of the 1.1mm objects also demonstrated good correlation with the 24{mu}m flux connected to massive star formation. This supports the hypothesis that the heating source of the cold dust is mainly local star-formation activity in the 1.1mm objects. The classification of the 1.1mm objects based on the existence of star-formation activity reveals the differences in the dust temperature, gas mass, and radius, which reflects the evolution sequence of GMCs.
- ID:
- ivo://CDS.VizieR/J/ApJ/727/114
- Title:
- BLAST 2005: a 10deg^2^ survey in Cygnus X
- Short Name:
- J/ApJ/727/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Cygnus X in a new multi-wavelength perspective based on an unbiased BLAST survey at 250, 350, and 500um, combined with rich data sets for this well-studied region. Our primary goal is to investigate the early stages of high-mass star formation. We have detected 184 compact sources in various stages of evolution across all three BLAST bands. From their well-constrained spectral energy distributions, we obtain the physical properties mass, surface density, bolometric luminosity, and dust temperature. Some of the bright sources reaching 40K contain well-known compact HII regions. We relate these to other sources at earlier stages of evolution via the energetics as deduced from their position in the luminosity-mass (L-M) diagram. The BLAST spectral coverage, near the peak of the spectral energy distribution of the dust, reveals fainter sources too cool (~10K) to be seen by earlier shorter-wavelength surveys like IRAS. We detect thermal emission from infrared dark clouds and investigate the phenomenon of cold "starless cores" more generally. Spitzer images of these cold sources often show stellar nurseries, but these potential sites for massive star formation are "starless" in the sense that to date there is no massive protostar in a vigorous accretion phase.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A8
- Title:
- Bubble HII region Sh2-39 (N5)
- Short Name:
- J/A+A/606/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Aiming at studying the physical properties of Galactic IR bubbles and to explore their impact in triggering massive star formation, we perform a multiwavelength analysis of the bubble HII region Sh2-39 (N5) and its environs. To analyze the molecular gas we use CO(3-2) and HCO^+^(4-3) line data obtained with the on-the-fly technique from the ASTE telescope. To study the distribution and physical characteristics of the dust, we make use of archival data from ATLASGAL, Herschel, and MSX, while the ionized gas was studied making use of an NVSS image. We use public WISE, Spitzer, and MSX point source catalogs to search for infrared candidate YSOs in the region. To investigate the stellar cluster [BDS2003] 6 we use IR spectroscopic data obtained with the ARCoIRIS spectrograph, mounted on Blanco 4-m Telescope at CTIO, and new available IR Ks band observations from the VVVeXtended ESO Public Survey (VVVX). The new ASTE observations allowed the molecular gas component in the velocity range from 30km/s to 46km/s, associated with Sh2-39, to be studied in detail. The morphology of the molecular gas suggests that the ionized gas is expanding against its parental cloud. We have identified four molecular clumps, that were likely formed by the expansion of the ionization front, and determined some of their physical and dynamical properties. Clumps having HCO^+^ and 870um counterparts show evidence of gravitational collapse. We identified several candidate YSOs across the molecular component. Their spatial distribution, as well as the fragmentation time derived for the collected layers of the molecular gas, suggest that massive star formation might have been triggered by the expansion of the nebula via the collect and collapse mechanism. The spectroscopical distance obtained for the stellar cluster [BDS2003] 6, placed over one of the collapsing clumps in the border of the HII region, reveals that this cluster is physically associated with the nebula and gives more support to the triggered massive star formation scenario. A radio continuum data analysis indicates that the nebula is older and expands at lower velocity than typical IR Galactic bubbles.
- ID:
- ivo://CDS.VizieR/J/ApJ/649/759
- Title:
- Bubbles in the galactic disk
- Short Name:
- J/ApJ/649/759
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A visual examination of the images from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) has revealed 322 partial and closed rings that we propose represent partially or fully enclosed three-dimensional bubbles. We argue that the bubbles are primarily formed by hot young stars in massive star formation regions. We have found an average of about 1.5 bubbles per square degree. About 25% of the bubbles coincide with known radio HII regions, and about 13% enclose known star clusters. It appears that B4B9 stars (too cool to produce detectable radio HII regions) probably produce about three-quarters of the bubbles in our sample, and the remainder are produced by young OB3 stars that produce detectable radio HII regions.
- ID:
- ivo://CDS.VizieR/J/ApJ/670/428
- Title:
- Bubbles in the galactic disk. II.
- Short Name:
- J/ApJ/670/428
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report 269 mid-infrared bubbles within 10{deg} of the Galactic center from visual inspection of the Spitzer GLIMPSE II Legacy Science program images. The surface density of bubbles is ~5deg^-2^ or about 3 times that detected in longitudes |l|=10{deg}-65{deg}, because the inner 10{deg} of longitude were more thoroughly searched for small bubbles. There is a gradient in the number of bubbles with longitude with an increase of about a factor of 2 from 2{deg} to 10{deg}; this is probably the result of several factors, including decreasing diffuse background brightness, confusion, and opacity with longitude. Bubble eccentricities are typically between 0.6 and 0.8, and >50% show evidence for blowouts, which we suggest result from local density fluctuations of the ISM and/or anisotropic stellar winds and radiation fields.
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/1202
- Title:
- BVI photometry in W5E HII region
- Short Name:
- J/MNRAS/415/1202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this paper is to present the results of photometric investigations of the central cluster of the W5 E HII region as well as a follow-up study of the triggered star formation in and around bright-rimmed clouds (BRCs). We have carried out wide-field UBVIc and deep VIc photometry of the W5 E HII region. A distance of ~2.1kpc and a mean age of ~1.3Myr have been obtained for the central cluster. The young stellar objects (YSOs) associated with the region are identified on the basis of near-infrared and mid-infrared observations.
- ID:
- ivo://CDS.VizieR/J/A+A/436/117
- Title:
- BVR photometry in N214C
- Short Name:
- J/A+A/436/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the Large Magellanic Cloud HII region N 214C using imaging and spectroscopy obtained at the ESO New Technology Telescope. On the basis of the highest resolution images so far obtained of the OB association LH 110, we show that the main exciting source of the HII region, Sk -71 51, is in fact a tight cluster of massive stars consisting of at least 6 components in an area ~4" wide. Spectroscopic observations allow us to revise the spectral type of the main component (#17) to O2V((f*))+OB, a very rare, hot type. We also classify several other stars associated with N 214C and study the extinction and excitation characteristics of the HII region. Moreover, we obtain BVR photometry and astrometry of 2365 stars and from the corresponding color-magnitude diagram study the stellar content of N 214C and the surrounding LH 110. Furthermore, we discover a striking compact blob of ionized gas in the outer northern part of N 214C. A spherical structure of ~5", in radius (~1.3pc), it is split into two lobes by absorbing dust running diametrically through its center. We discuss the possible nature of this object.
- ID:
- ivo://CDS.VizieR/J/MNRAS/440/1080
- Title:
- Calibration of H{alpha} fluxes in SHS
- Short Name:
- J/MNRAS/440/1080
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The AAO/UKST SuperCOSMOS H{alpha} Survey (SHS) was, when completed in 2003, a powerful addition to extant wide-field surveys. The combination of areal coverage, spatial resolution and sensitivity in a narrow imaging band, still marks it out today as an excellent resource for the astronomical community. The 233 separate fields are available online in digital form, with each field covering 25deg^2^. The SHS has been the motivation for equivalent surveys in the north, and new digital H{alpha} surveys now beginning in the south such as VPHAS+. It has been the foundation of many important discovery projects with the Macquarie/AAO/Strasbourg H{alpha} planetary nebula project being a particularly successful example. However, the full potential of the SHS has been hampered by lack of a clear route to acceptable flux calibration from the base photographic data. We have determined the calibration factors for 170 individual SHS fields, and present a direct pathway to the measurement of integrated H{alpha} fluxes and surface brightnesses for resolved nebulae detected in the SHS. We also include a catalogue of integrated H{alpha} fluxes for >100 planetary and other nebulae measured from the SHS, and use these data to show that fluxes, accurate to +/-0.10-0.14dex (~25-35%), can be obtained from these fields. For the remaining 63 fields, a mean calibration factor of 12.0 counts/pixel/R can be used, allowing the determination of reasonable integrated fluxes accurate to better than +/-0.2dex (~50%). We outline the procedures involved and the caveats that need to be appreciated in achieving such flux measurements. This paper forms a handy reference source that will significantly increase the scientific utility of the SHS.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/61
- Title:
- Candidate X-ray OB stars in MYStIX regions
- Short Name:
- J/ApJ/838/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive O-type and early B-type (OB) stars in the nearby Galaxy remain incompletely cataloged due to high extinction, bright visible and infrared nebular emission in H II regions, and high field star contamination. These difficulties are alleviated by restricting the search to stars with X-ray emission. Using the X-ray point sources from the Massive Young Star-forming Complex Study in Infrared and X-Rays (MYStIX) survey of OB-dominated regions, we identify 98 MYStIX candidate OB (MOBc) stars by fitting their 1-8{mu}m spectral energy distributions (SEDs) with reddened stellar atmosphere models. We identify 27 additional MOBc stars based on JHK_S_ photometry of X-ray stars lacking SED fitting. These candidate OB stars indicate that the current census of stars earlier than B1, taken across the 18 MYStIX regions studied, is less than 50% complete. We also fit the SEDs of 239 previously published OB stars to measure interstellar extinction and bolometric luminosities, revealing six candidate massive binary systems and five candidate O-type (super)giants. As expected, candidate OB stars have systematically higher extinction than previously published OB stars. Notable results for individual regions include identification of the OB population of a recently discovered massive cluster in NGC 6357, an older OB association in the M17 complex, and new massive luminous O stars near the Trifid Nebula. In several relatively poorly studied regions (RCW 38, NGC 6334, NGC 6357, Trifid, and NGC 3576), the OB populations may increase by factors of 2.
