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- ID:
- ivo://CDS.VizieR/J/A+A/569/A20
- Title:
- Massive stars in two giant molecular clouds
- Short Name:
- J/A+A/569/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young massive stars and stellar clusters continuously form in the Galactic disk, generating new HII regions within their natal giant molecular clouds and subsequently enriching the interstellar medium via their winds and supernovae. Massive stars are among the brightest infrared stars in such regions; their identification permits the characterisation of the star formation history of the associated cloud as well as constraining the location of stellar aggregates and hence their occurrence as a function of global environment. We present a stellar spectroscopic survey in the direction of the giant molecular cloud G23.3-0.3. This complex is located at a distance of ~4-5kpc, and consists of several HII regions and supernova remnants. We discovered 11 Of_K_^+^ stars, one candidate luminous blue variable, several OB stars, and candidate red supergiants. Stars with K-band extinction from ~1.3-1.9mag appear to be associated with the GMC G23.3-0.3; O and B-types satisfying this criterion have spectrophotometric distances consistent with that of the giant molecular cloud. Combining near-IR spectroscopic and photometric data allowed us to characterize the multiple sites of star formation within it. The O-type stars have masses from ~25-45M_{sun}_, and ages of 5-8Myr. Two new red supergiants were detected with interstellar extinction typical of the cloud; along with the two RSGs within the cluster GLIMPSE9, they trace an older burst with an age of 20-30Myr. Massive stars were also detected in the core of three supernova remnants - W41, G22.7-0.2, and G22.7583-0.4917. A large population of massive stars appears associated with the GMC G23.3-0.3, with the properties inferred for them indicative of an extended history of stars formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/876/70
- Title:
- Massive YSOs in the IR dark cloud G79.3+0.3
- Short Name:
- J/ApJ/876/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- G79.3+0.3 is an infrared dark cloud in the Cygnus-X complex that is home to massive deeply embedded young stellar objects (YSOs). We have produced a Submillimeter Array (SMA) 1.3mm continuum image and ^12^CO line maps of the eastern section of G79.3+0.3 in which we detect five separate YSOs. We have estimated physical parameters for these five YSOs and others in the vicinity of G79.3+0.3 by fitting existing photometry from Spitzer, Herschel, and ground-based telescopes to spectral energy distribution models. Through these model fits we find that the most massive YSOs seen in the SMA 1.3mm continuum emission have masses in the 5-6M_{sun}_ range. One of the SMA sources was observed to power a massive collimated ^12^CO outflow extending at least 0.94pc in both directions from the protostar, with a total mass of 0.83M_{sun}_ and a dynamical timescale of 23kyr.
- ID:
- ivo://CDS.VizieR/J/AZh/84/839
- Title:
- Methanol emission of isolated maser condensations
- Short Name:
- J/AZh/84/839
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distribution of the radial velocities of class I methanol masers relative to the velocities of their parent molecular clouds is analyzed. This analysis is based on catalog data for methanol masers detected up to the present time in both the northern and southern hemispheres, together with catalog data for the CS(2-1) line, which traces dense, quiescent gas. Results for a large sample of sources show that, in contrast to class II methanol masers, which undergo Keplerian motions in protoplanetary disks, class I methanol masers retain their velocities in the local system of rest of the surrounding medium, and do not participate in the ejection of matter in bipolar out flows. They can be adequately described using a model in which matter ejected from active parts of the associated star-forming regions flows around isolated maser condensations. This compresses the maser clumps, enhancing the concentration of methanol and facilitating collisional pumping of the masers.
- ID:
- ivo://CDS.VizieR/J/AZh/79/328
- Title:
- Methanol maser condensations in W 48
- Short Name:
- J/AZh/79/328
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The methanol-line spectra in two maser condensations at velocities ~41 and ~45km/s in the star-forming region W 48 have been studied.
- ID:
- ivo://CDS.VizieR/J/AZh/79/610
- Title:
- Methyl acetylene observations of warm clouds
- Short Name:
- J/AZh/79/610
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a survey of 63 galactic star-forming region in the 6k-5k and 5k-4k methyl acetylene lines at 102.5 and 85.5GHz are presented. Fourty-three sources were detected at 102.5GHz, and twenty-five at 85.5GHz
- ID:
- ivo://CDS.VizieR/J/A+A/636/A16
- Title:
- M43, Horsehead, MonR2, M17SW [CII]158um spectra
- Short Name:
- J/A+A/636/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The [CII] 158um FIR fine-structure line is one of the most important cooling lines of the star-forming ISM. It is used as a tracer of star formation efficiency in external galaxies and to study feedback effects in parental clouds. High spectral resolution observations have shown complex structures in the line profiles of the [CII] emission. To determine whether the complex profiles observed in [^12^CII] are due to individual velocity components along the line-of-sight or due to self-absorption, one has to compare the [^12^CII] and isotopic [^13^CII] line profiles. Deep integrations with the SOFIA/upGREAT 7-pixel array receiver in the sources M43, Horsehead PDR, Monoceros R2 and M17 SW allow to detect with high S/N the optically thin [^13^CII] and simultaneously the [^12^CII] emission lines. We first derive the [^12^CII] optical depth and the [CII] column density from a single component model. However, the complex line profiles observed require a double layer model with an emitting background and an absorbing foreground. A multi-component velocity fit allows to derive the physical conditions of the [CII] gas: column density and excitation temperature. We find moderate to high [^12^CII] optical depths in all four sources, and self-absorption of [^12^CII] in Mon R2 and M17 SW. The high column density of the warm background emission corresponds to an equivalent Av of up to 41mag. The foreground absorption requires substantial column densities of cold and dense [CII] gas, with an equivalent Av ranging up to about 13mag. The column density of the warm background material requires multiple PDR surfaces stacked along the line of sight and in velocity. The substantial column density of dense and cold foreground [CII] gas detected in absorption cannot be explained with any known scenario and we can only speculate about its origin.
- ID:
- ivo://CDS.VizieR/J/ApJ/702/1507
- Title:
- Mid-IR photometry in IC 1396A
- Short Name:
- J/ApJ/702/1507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used Spitzer/Infrared Array Camera (IRAC) to conduct a photometric monitoring program of the IC1396A dark globule in order to study the mid-IR (3.6-8um) variability of the heavily embedded young stellar objects (YSOs) present in that area. We obtained light curves covering a 14 day timespan with a twice daily cadence for 69 YSOs, and continuous light curves with approximately 12s cadence over 7hr for 38 YSOs. Typical accuracies for our relative photometry were 1%-2% for the long timespan data and a few millimagnitude, corresponding to less than 0.5%, for the 7hr continuous "staring-mode" data. More than half of the YSOs showed detectable variability, with amplitudes from ~0.05mag to ~0.2mag. One star, IC1396A-47, shows a 3.5hr periodic light curve; this object may be a PMS Delta Scuti star.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A135
- Title:
- Mid-J CO emission of Top100 clumps
- Short Name:
- J/A+A/622/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-mass stars are formed within massive molecular clumps, where a large number of stars form close together. The evolution of the clumps with different masses and luminosities is mainly regulated by their high-mass stellar content and the formation of such objects is still not well understood. In this work, we characterise the mid-J CO emission in a statistical sample of 99 clumps (TOP100) selected from the ATLASGAL survey that are representative of the Galactic proto-cluster population. High-spatial resolution APEX-CHAMP+ maps of the CO (6-5) and CO (7-6) transitions were obtained and combined with additional single-pointing APEX-FLASH+ spectra of the CO (4-3) line. The data were convolved to a common angular resolution of 13.4". We analysed the line profiles by fitting the spectra with up to three Gaussian components, classified as narrow or broad, and computed CO line luminosities for each transition. Additionally, we defined a distance-limited sample of 72 sources within 5kpc to check the robustness of our analysis against beam dilution effects. We have studied the correlations of the line luminosities and profiles for the three CO transitions with the clump properties and investigate if and how they change as a function of the evolution. All sources were detected above 3-{sigma} in all three CO transitions and most of the sources exhibit broad CO emission likely associated with molecular outflows. We find that the extension of the mid-J CO emission is correlated with the size of the dust emission traced by the Herschel-PACS 70um maps. The CO line luminosity (LCO) is correlated with the luminosity and mass of the clumps. However, it does not correlate with the luminosity-to-mass ratio. The dependency of the CO luminosity with the properties of the clumps is steeper for higher-J transitions. Our data seem to exclude that this trend is biased by self-absorption features in the CO emission, but rather suggest that different J transitions arise from different regions of the inner envelope. Moreover, high-mass clumps show similar trends in CO luminosity as lower mass clumps, but are systematically offset towards larger values, suggesting that higher column density and (or) temperature (of unresolved) CO emitters are found inside high-mass clumps.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A96
- Title:
- Mid-J CO shock tracing observations of IRDCs II
- Short Name:
- J/A+A/587/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Infrared dark clouds are kinematically complex molecular structures in the interstellar medium that can host sites of massive star formation. We present maps measuring 4 square arcminutes of the ^12^CO, ^13^CO, and C^18^O J=3 to 2 lines from selected locations within the C and F (G028.37+00.07 and G034.43+00.24) infrared dark clouds (IRDCs), as well as single pointing observations of the ^13^CO and C^18^O J=2 to 1 lines towards three cores within these clouds. We derive CO gas temperatures throughout the maps and find that CO is significantly frozen out within these IRDCs. We find that the CO depletion tends to be the highest near column density peaks with maximum depletion factors between 5 and 9 in IRDC F and between 16 and 31 in IRDC C. We also detect multiple velocity components and complex kinematic structure in both IRDCs. Therefore, the kinematics of IRDCs seem to point to dynamically evolving structures yielding dense cores with considerable depletion factors.
