- ID:
- ivo://CDS.VizieR/J/ApJS/251/29
- Title:
- Stellar bow shock nebulae spectroscopic obs.
- Short Name:
- J/ApJS/251/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Arcuate mid-infrared nebulae known as stellar bow shock nebulae (SBNe) have been previously hypothesized to be supported by the strong stellar winds and/or luminosity of massive early-type stars. We present an optical spectroscopic survey of 84 stars identified from mid-infrared images as candidate SBN-supporting stars. Eighty-one of 84 sources, 96%, are O or early-B spectral types. K-band luminosities for a larger sample of 289 stars at the centers of bow shock nebulae are overwhelmingly consistent with OB stars. This affirms both that SBNe are supported by massive stars and that arcuate mid-infrared nebulae are reliable indicators of the presence of a massive star. The radial velocity dispersions of these systems and detections of double-lined systems indicate that at least 27 of the 74 systems with multiple observations (>36%) are candidate multiple-star systems. This rate is consistent with observed multiplicity rates of field OB stars detected with similar radial velocity surveys and lower than, but not inconsistent with, the multiplicity rates of OB stars in clusters and associations.
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- ID:
- ivo://CDS.VizieR/J/A+A/618/A163
- Title:
- Stokes param. of Bok globules background stars
- Short Name:
- J/A+A/618/A163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The role of magnetic fields in the process of star formation is a matter of continuous debate. Clear observational proof of the general influence of magnetic fields on the early phase of cloud collapse is still pending. In an earlier study on Bok globules with simple structures, we find strong indications of dominant magnetic fields across large spatial scales. The aim of this study is to test the magnetic field influence across Bok globules with more complex density structures. We apply near-infrared polarimetry to trace the magnetic field structure on scales of 10^4^-10^5^au in selected Bok globules. The combination of these measurements with archival data in the optical and sub-mm wavelength range allows us to characterize the magnetic field on scales of 10^3^-10^6^au. We present polarimetric data in the near-infrared wavelength range for the three Bok globules CB34, CB56, and [OMK2002] 18, combined with archival polarimetric data in the optical wavelength range for CB34 and CB56, and in the sub millimeter wavelength range for CB34 and [OMK2002] 18. We find a strong polarization signal (P>2%) in the near-infrared for all three globules. For CB34, we detect a connection between the structure on scales of 10^4^-10^5^au to 10^5^-10^6^au. For CB56, we trace aligned polarization segments in both the near-infrared and optical data, suggesting a connection of the magnetic field structure across the whole globule. In the case of [OMK2002]18, we find ordered polarization structures on scales of 10^4^-10^5^au. We find strongly aligned polarization segments on large scales which indicate dominant magnetic fields across Bok globules with complex density structures. To reconcile our findings in globules, the lowest mass clouds known, and the results on intermediate (e.g. Taurus) and more massive (e.g. Orion) clouds, we postulate a mass dependent role of magnetic fields, whereby magnetic fields appear to be dominant on low and high mass but rather sub dominant on intermediate mass clouds.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A144
- Title:
- Strongly lensed submm galaxies CO spectra
- Short Name:
- J/A+A/608/A144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the IRAM-30m observations of multiple-J CO (J_up_ mostly from 3 up to 8) and [CI](^3^P_2_ -> ^3^P_1_) ([CI](2-1) hereafter) line emission in a sample of redshift ~2-4 submillimeter galaxies (SMGs). These SMGs are selected among the brightest lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). 47 CO lines and 7 [CI](2-1) lines have been detected in 15 lensed SMGs. A non-negligible effect of differential lensing is found for the CO emission lines, which could have caused significant underestimations of the linewidths, hence of the dynamical masses. The CO spectral line energy distributions (SLEDs), peaking around J_up_~5-7, are found to be similar to those of the local starburst-dominated ultra-luminous infrared galaxies and of the previously studied SMGs. After correcting for lensing amplification, we derived the global properties of the bulk of molecular gas in the SMGs using non-LTE radiative transfer modelling, such as the molecular gas density n_H2_~10^2.5^-10^4.1^cm^-3^ and the kinetic temperature T_k_~20-750K. The gas thermal pressure P_{th} ranging from ~10^5^K/cm^3^ to 10^6^K/cm^3^ is found to be correlated with star formation efficiency. Further decomposing the CO SLEDs into two excitation components, we find a low-excitation component with n_H2_~10^2.8^-10^4.6^cm^-3^ and T_k_~20-30K, which is less correlated with star formation, and a high-excitation one (n_H2_~10^2.7^-10^4.2^cm^-3^, T_k_~60-400K) which is tightly related to the on-going star-forming activity. Additionally, tight linear correlations between the far-infrared and CO line luminosities have been confirmed for the J_up_>=5 CO lines of these SMGs, implying that these CO lines are good tracers of star formation. The [CI](2-1) lines follow the tight linear correlation between the luminosities of the [CI](2-1) and the CO(1-0) line found in local starbursts, indicating that [CI] lines could serve as good total molecular gas mass tracers for high-redshift SMGs as well. The total mass of the molecular gas reservoir, (1-30)x10^10^M_{sun}_, derived based on the CO(3-2) fluxes and {alpha}_CO(1-0)_=0.8M_{sun}_/(K.km/s/pc^2), suggests a typical molecular gas depletion time t_dep_~20-100Myr and a gas to dust mass ratio {delta}_GDR_~30-100 with ~20%-60% uncertainty for the SMGs. The ratio between CO line luminosity and the dust mass L'_CO(1-0)_/M_{dust} appears to be slowly increasing with redshift for high-redshift SMGs, which CO need to be further confirmed by a more complete SMG sample at various redshifts. Finally, through comparing the linewidth of CO and H_2_O lines, we find that they agree well in almost all our SMGs, confirming that the emitting regions of the CO and H_2_O lines are co-spatially located.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A107
- Title:
- (Sub)millimeter RRL in high-mass star-forming clumps
- Short Name:
- J/A+A/616/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous radio recombination line (RRL) observations of dust clumps identified in the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) have led to the detection of a large number of RRLs in the 3mm range. Here, we aim to study their excitation with shorter wavelength (sub)millimeter radio recombination line (submm-RRL) observations. We made observations of submm-RRLs with low principal quantum numbers (n<=30) using the APEX 12m telescope, toward 104 HII regions associated with massive dust clumps from ATLASGAL. The observations covered the H25{alpha}, H28{alpha}, and H35{beta} transitions. Toward a small subsample the H26{alpha}, H27{alpha}, H29{alpha}, and H30{alpha} lines were observed to avoid contamination by molecular lines at adjacent frequencies. We have detected submm-RRLs (signal-to-noise >=3{sigma}) from compact HII regions embedded within 93 clumps. The submm-RRLs are approximately a factor of two brighter than the mm-RRLs and consistent with optically thin emission in local thermodynamic equilibrium (LTE). The average ratio (0.31) of the measured H35{beta}/H28{alpha} fluxes is close to the LTE value of 0.28. No indication of RRL maser emission has been found. The Lyman photon flux, bolometric, and submm-RRL luminosities toward the submm-RRL detected sources present significant correlations. The trends of dust temperature and the ratio of bolometric luminosity to clump mass, L_bol_/M_clump_, indicate that the HII regions are related to L_bol_/M_clump_, indicate that the HII regions are related to the most massive and luminous clumps. By estimating the production rate of ionizing photons, Q, from the submm-RRL flux, we find that the Q(H28{alpha}) measurements provide estimates of the Lyman continuum photon flux consistent with those determined from 5GHz radio continuum emission. Six RRL sources show line profiles that are a combination of a narrow and a broad Gaussian feature. The broad features are likely associated with high-velocity ionized flows. We have detected submm-RRLs toward 93 ATLASGAL clumps. Six RRL sources have high-velocity RRL components likely driven by high-velocity ionized flows. Their observed properties are consistent with thermal emission that correlates well with the Lyman continuum flux of the HII regions. The sample of HII regions with mm/submm-RRL detections probes, in our Galaxy, luminous clumps (L_bol_>10^4^L_{sun}_) with high L_bol_/M_clump_. We also provide suitable candidates for further studies of the morphology and kinematics of embedded, compact HII regions with the Atacama Large Millimeter/submillimeter Array (ALMA).
- ID:
- ivo://CDS.VizieR/J/A+A/543/A46
- Title:
- Submillimeter spectrum of HCOOCD_2_H
- Short Name:
- J/A+A/543/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Astronomical surveys of interstellar molecules, such as those that will be available with the very sensitive ALMA telescope, require preliminary laboratory investigations of the microwave and submillimeter-wave spectra of new molecular species to identify these in the interstellar media. We build a linelist that should allow us to detect HCOOCD_2_H, provided it is present in the interstellar media in a suitable concentration.
- ID:
- ivo://CDS.VizieR/J/ApJ/644/990
- Title:
- Sub-mm clumps at 450 and 850{mu}m in M17
- Short Name:
- J/ApJ/644/990
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have mapped a 5.5x5.5pc portion of the M17 massive star-forming region in both 850 and 450{mu}m dust continuum emission using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). The maps reveal more than 100 dusty clumps with deconvolved linear sizes of ~0.05-0.2pc and masses of ~0.8-120M_{sun}_, most of which are not associated with known mid-infrared point sources. Fitting the clump mass function with a double power law gives a mean power-law exponent of {alpha}high=-2.4+/-0.3 for the high-mass power law, consistent with the exponent of the Salpeter stellar mass function. We show that a lognormal clump mass distribution with a peak at 4M_{sun}_ produces as good a fit to the clump mass function as does a double power law. This 4M_{sun}_ peak mass is well above the peak masses of both the stellar initial mass function and the mass function of clumps in low-mass star-forming regions. Despite the difference in intrinsic mass scale, the shape of the M17 clump mass function appears to be consistent with the shape of the core mass function in low-mass star-forming regions. Thus, we suggest that the clump mass function in high-mass star-forming regions may be a scaled up version of that in low-mass regions, instead of its extension to higher masses.
- ID:
- ivo://CDS.VizieR/J/ApJ/639/259
- Title:
- Sub-mm clumps in Orion B South molecular cloud
- Short Name:
- J/ApJ/639/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a survey of a 1300arcmin^2^ region of the Orion B South molecular cloud, including NGC 2024, NGC 2023, and the Horsehead Nebula (B33), obtained using the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). Submillimeter continuum observations at 450 and 850{mu}m are discussed. Using an automated algorithm, 57 discrete emission features ("clumps") are identified in the 850{mu}m map.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A32
- Title:
- Sub-mm images of SSTB213 J041757.75+274105.5
- Short Name:
- J/A+A/564/A32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed the proto brown dwarf candidate SSTB213 J041757 with the Submillimeter Array to search for CO molecular outflow emission from the source. Our CO maps do not show any outflow emission from the proto brown dwarf candidate. The non-detection implies that the molecular outflows from the source are weak; deeper observations are therefore needed to probe the outflows from the source.
- ID:
- ivo://CDS.VizieR/J/ApJ/559/307
- Title:
- Sub-mm mapping in Orion B molecular cloud
- Short Name:
- J/ApJ/559/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a survey of a 900 arcmin^2^ region of the Orion B molecular cloud, including NGC 2068, NGC 2071, and HH 24/25/26, at 850{mu}m using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. Following the techniques developed by Johnstone et al. (2000ApJ...545..327J), we identify 75 independent objects and compute size, flux, and degree of central concentration. Comparison with isothermal, pressure-confined, self-gravitating Bonnor-Ebert spheres implies that the clumps have internal temperatures of 20-40K and surface pressures 5.5<log(P/k)[CGS]<6.5. The clump masses span 0.2-12.3M_{sun}_ assuming typical dust temperatures and a dust emissivity {kappa}_850_=0.01cm^2^/g.
- ID:
- ivo://CDS.VizieR/J/A+A/481/411
- Title:
- submm point sources from the Archeops experiment
- Short Name:
- J/A+A/481/411
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Archeops is a balloon-borne experiment, mainly designed to measure the Cosmic Microwave Background (CMB) temperature anisotropies at high angular resolution (~12 arcminutes). By-products of the mission are shallow sensitivity maps over a large fraction of the sky (about 30 %) in the millimetre and submillimetre range at 143, 217, 353 and 545GHz. From these maps, we produce a catalog of bright submillimetre point sources. We present in this paper the processing and analysis of the Archeops point sources. Redundancy across detectors is the key factor allowing us to distinguish glitches from genuine point sources in the 20 independent maps. We look at the properties of the most reliable point sources, totalling 304. Fluxes range from 1 to 10000Jy (at the frequencies covering 143 to 545GHz). All sources are either planets (2) or of galactic origin. The longitude range is from 75 to 198-degrees. Some of the sources are associated with the well-known Lynds Nebulae and HII compact regions in the galactic plane. A large fraction of the sources have an IRAS counterpart. Except for Jupiter, Saturn, the Crab and Cas A, all sources show a dust-emission-like modified blackbody emission spectrum. Temperatures cover a range from 7 to 27K. For the coldest sources (T<10K), a steep nu^beta^ emissivity law is found with a surprising beta~3 to 4. An inverse relationship between T and beta is observed. The number density of sources at 353GHz with flux brighter than 100Jy is of the order of 1 per degree of Galactic longitude. These sources will provide a strong check for the calibration of the Planck HFI focal plane geometry as a complement to planets. These very cold sources observed by Archeops should be prime targets for mapping observations by the Akari and Herschel space missions and ground-based observatories.
