- ID:
- ivo://CDS.VizieR/J/ApJ/835/3
- Title:
- 218GHz obs. of embedded protostars in Ophiuchus
- Short Name:
- J/ApJ/835/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present APEX 218GHz observations of molecular emission in a complete sample of embedded protostars in the Ophiuchus star-forming region. To study the physical properties of the cores, we calculate H_2_CO and c-C_3_H_2_ rotational temperatures, both of which are good tracers of the kinetic temperature of the molecular gas. We find that the H_2_CO temperatures range between 16K and 124K, with the highest H_2_CO temperatures toward the hot corino source IRAS 16293-2422 (69-124K) and the sources in the {rho} Oph A cloud (23-49K) located close to the luminous Herbig Be star S1, which externally irradiates the {rho} Oph A cores. On the other hand, the c-C_3_H_2_ rotational temperature is consistently low (7-17K) in all sources. Our results indicate that the c-C_3_H_2_ emission is primarily tracing more shielded parts of the envelope whereas the H_2_CO emission (at the angular scale of the APEX beam; 3600 au in Ophiuchus) mainly traces the outer irradiated envelopes, apart from in IRAS 16293-2422, where the hot corino emission dominates. In some sources, a secondary velocity component is also seen, possibly tracing the molecular outflow.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/777/157
- Title:
- 90GHz obs. of high-mass star-forming regions
- Short Name:
- J/ApJ/777/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical changes of high-mass star-forming regions provide a potential method for classifying their evolutionary stages and, ultimately, ages. In this study, we search for correlations between molecular abundances and the evolutionary stages of dense molecular clumps associated with high-mass star formation. We use the molecular line maps from Year 1 of the Millimetre Astronomy Legacy Team 90GHz (MALT90) Survey. The survey mapped several hundred individual star-forming clumps chosen from the ATLASGAL survey to span the complete range of evolution, from prestellar to protostellar to H II regions. The evolutionary stage of each clump is classified using the Spitzer GLIMPSE/MIPSGAL mid-IR surveys. Where possible, we determine the dust temperatures and H_2_ column densities for each clump from Herschel/Hi-GAL continuum data. From MALT90 data, we measure the integrated intensities of the N_2_H^+^, HCO^+^, HCN and HNC(1-0) lines, and derive the column densities and abundances of N_2_H^+^ and HCO^+^. The Herschel dust temperatures increase as a function of the IR-based Spitzer evolutionary classification scheme, with the youngest clumps being the coldest, which gives confidence that this classification method provides a reliable way to assign evolutionary stages to clumps. Both N_2_H^+^ and HCO^+^ abundances increase as a function of evolutionary stage, whereas the N_2_H^+^(1-0) to HCO^+^(1-0) integrated intensity ratios show no discernable trend. The HCN(1-0) to HNC(1-0) integrated intensity ratios show marginal evidence of an increase as the clumps evolve.
- ID:
- ivo://CDS.VizieR/J/ApJ/750/170
- Title:
- 6.035GHz OH observations of two IRAS
- Short Name:
- J/ApJ/750/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 6.035GHz hydroxyl (OH) maser flares toward the massive star-forming region IRAS 18566+0408 (G37.55+0.20), which is the only region known to show periodic formaldehyde (4.8GHz H_2_CO) and methanol (6.7GHz CH_3_OH) maser flares. The observations were conducted between 2008 October and 2010 January with the 305m Arecibo Telescope in Puerto Rico. We detected two flare events, one in 2009 March and one in 2009 September to November. The OH maser flares are not simultaneous with the H_2_ CO flares, but may be correlated with CH_3_ OH flares from a component at corresponding velocities. A possible correlated variability of OH and CH_3_ OH masers in IRAS 18566+0408 is consistent with a common excitation mechanism (IR pumping) as predicted by theory.
- ID:
- ivo://CDS.VizieR/J/ApJ/845/44
- Title:
- 340GHz SMA obs. of 50 nearby protoplanetary disks
- Short Name:
- J/ApJ/845/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a survey at subarcsecond resolution of the 340GHz dust continuum emission from 50 nearby protoplanetary disks, based on new and archival observations with the Submillimeter Array. The observed visibility data were modeled with a simple prescription for the radial surface brightness profile. The results were used to extract intuitive, empirical estimates of the emission "size" for each disk, R_eff_, defined as the radius that encircles a fixed fraction of the total continuum luminosity, L_mm_. We find a significant correlation between the sizes and luminosities, such that R_eff_{propto}L_mm_^0.5^, providing a confirmation and quantitative characterization of a putative trend that was noted previously. This correlation suggests that these disks have roughly the same average surface brightness interior to their given effective radius, ~0.2Jy/arcsec^2^ (or 8K in brightness temperature). The same trend remains, but the 0.2dex of dispersion perpendicular to this relation essentially disappears, when we account for the irradiation environment of each disk with a crude approximation of the dust temperatures based on the stellar host luminosities. We consider two (not mutually exclusive) explanations for the origin of this size-luminosity relationship. Simple models of the growth and migration of disk solids can account for the observed trend for a reasonable range of initial conditions, but only on timescales that are much shorter than the nominal ages present in the sample. An alternative scenario invokes optically thick emission concentrated on unresolved scales, with filling factors of a few tens of percent, which is perhaps a manifestation of localized particle traps.
- ID:
- ivo://CDS.VizieR/J/A+A/325/1163
- Title:
- 330-360GHz spectral lines of G 34.3+0.15. II.
- Short Name:
- J/A+A/325/1163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Tables 5 and 6 present calculated column densities (in units of molecules per cm^2^) of various species in the ultracompact core (UCC), the compact core (CC) and the halo, together with the total column density and the observed column density where available. Table 5 gives column densities at a time of 3x10^3yrs in the UCC and CC components and at 10^5yrs in the halo. Table 6 gives column densities at a time of 10^4yrs in the UCC and CC components and 10^5yrs in the halo.
- ID:
- ivo://CDS.VizieR/J/ApJ/699/1092
- Title:
- Giant molecular clouds (SRBY)
- Short Name:
- J/ApJ/699/1092
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The properties of Galactic molecular clouds tabulated by Solomon et al. (SRBY; 1987ApJ...319..730S) are re-examined using the Boston University-FCRAO Galactic Ring Survey of ^13^COJ=1-0 emission. These new data provide a lower opacity tracer of molecular clouds and improved angular and spectral resolution compared with previous surveys of molecular line emission along the Galactic Plane. We calculate giant molecular cloud (GMC) masses within the SRBY cloud boundaries assuming local thermodynamic equilibrium (LTE) conditions throughout the cloud and a constant H_2_ to ^13^CO abundance, while accounting for the variation of the ^12^C/^13^C with galactocentric radius.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A53
- Title:
- Giant molecular filament GMF54 images
- Short Name:
- J/A+A/641/A53
- Date:
- 07 Mar 2022 07:18:57
- Publisher:
- CDS
- Description:
- Recent surveys of the Galactic plane in the dust continuum and CO emission lines reveal that large (>~50pc) and massive (>~10^5^M_{sun}_) filaments, know as giant molecular filaments (GMFs), may be linked to galactic dynamics and trace the mid-plane of the gravitational potential in the Milky Way. Yet our physical understanding of GMFs is still poor. We investigate the dense gas properties of one GMF, with the ultimate goal of connecting these dense gas tracers with star formation processes in the GMF. We have imaged one entire GMF located at l~52-54{deg} longitude, GMF54 (~68pc long), in the empirical dense gas tracers using the HCN(1-0), HNC(1-0), HCO^+^(1-0) lines, and their ^13^C isotopologue transitions, as well as the N_2_H^+^1-0) line. We study the dense gas distribution, the column density probability density functions (N-PDFs) and the line ratios within the GMF. The dense gas molecular transitions follow the extended structure of the filament with area filling factors between 0.06 and 0.28 with respect to ^13^CO(1-0). We constructed the N-PDFs of H_2_ for each of the dense gas tracers based on their column densities and assumed uniform abundance. The N-PDFs of the dense gas tracers appear curved in log-log representation, and the HCO^+^ NPDF has the largest log-normal width and flattest power-law slope index. Studying the N-PDFs for sub-regions of GMF54, we found an evolutionary trend in the N-PDFs that high-mass star forming and Photon Dominated Regions (PDRs) have flatter power-law indices. The integrated intensity ratios of the molecular lines in GMF54 are comparable to those in nearby galaxies. In particular, the N_2_H^+^/^13^CO ratio, which traces the dense gas fraction, has similar values in GMF54 and all nearby galaxies except Ultraluminous Infrared Galaxies (ULIRGs). As the largest coherent cold gaseous structure in our Milky Way, GMFs, are outstanding candidates for connecting studies of star formation on Galactic and extragalactic scales. By analyzing a complete map of the dense gas in a GMF we have found that: (1) the dense gas N-PDFs appear flatter in more evolved regions and steeper in younger regions, and (2) its integrated dense gas intensity ratios are similar to those of nearby galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/634/A139
- Title:
- Giant Molecular Filament THOR datacubes
- Short Name:
- J/A+A/634/A139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Molecular clouds form from the atomic phase of the interstellar medium. However, characterizing the transition between the atomic and the molecular interstellar medium (ISM) is a complex observational task. Here we address cloud formation processes by combining HI self absorption (HISA) with molecular line data. Column density probability density functions (N-PDFs) are a common tool for examining molecular clouds. One scenario proposed by numerical simulations is that the N-PDF evolves from a log-normal shape at early times to a power-law-like shape at later times. To date, investigations of N-PDFs have been mostly limited to the molecular component of the cloud. In this paper, we study the cold atomic component of the giant molecular filament GMF38.1-32.4a (GMF38a, distance=3.4kpc, length~230pc), calculate its N-PDFs, and study its kinematics. We identify an extended HISA feature, which is partly correlated with the ^13^CO emission. The peak velocities of the HISA and 13CO observations agree well on the eastern side of the filament, whereas a velocity offset of approximately 4km/s is found on the western side. The sonic Mach number we derive from the linewidth measurements shows that a large fraction of the HISA, which is ascribed to the cold neutral medium (CNM), is at subsonic and transonic velocities. The column density of the CNM part is on the order of 10^20^ to 10^21^cm^-2^. The column density of molecular hydrogen, traced by ^13^CO, is an order of magnitude higher. The N-PDFs from HISA (CNM), HI emission (the warm and cold neutral medium), and 13CO (molecular component) are well described by log-normal functions, which is in agreement with turbulent motions being the main driver of cloud dynamics. The N-PDF of the molecular component also shows a power law in the high column-density region, indicating self-gravity. We suggest that we are witnessing two different evolutionary stages within the filament. The eastern subregion seems to be forming a molecular cloud out of the atomic gas, whereas the western subregion already shows high column density peaks, active star formation, and evidence of related feedback processes.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A14
- Title:
- GIBS sources equivalent widths
- Short Name:
- J/A+A/645/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We developed a set of procedures to automatically detect and measure the DIB around 8620{AA} (the Gaia DIB) for a wide range of temperatures. The method was tested on about 5000 spectra from the Giraffe Inner Bulge Survey (GIBS; Zoccali et al., 2014A&A...562A..66Z), and 4194 reasonable fitting results were got. We made use of the reddenings, E(J-Ks), from the extinction map developed by Surot et al. (2020arXiv201002723S). A linear correlation between the equivalent width (EW) and E(J-Ks) was derived as E(J-Ks)/EW = 1.875, according to E(B-V)/EW = 2.721, which is highly consistent with previous results toward similar sightlines. After a correction based on the Vista Variables in the Via Lactea (VVV; Minniti et al., 2010NewA...15..433M) database for both EW and E(J-Ks), the coefficient derived from individual GIBS fields, E(J-Ks)/EW=1.884, is also in perfect agreement with literature values. Based on a subsample of 1015 stars toward the Galactic center, we determined a rest-frame wavelength of the Gaia DIB as 8620.55{AA}. A Gaussian profile is proved to be a proper and stable assumption for the Gaia DIB as no intrinsic asymmetry is found.
- ID:
- ivo://CDS.VizieR/J/ApJ/793/92
- Title:
- Global properties of z=1~2 GMASS galaxies
- Short Name:
- J/ApJ/793/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a study of the 2300-2600 {AA} Fe II/Fe II* multiplets in the rest-UV spectra of star-forming galaxies at 1.0<z<2.6 as probes of galactic-scale outflows. We extracted a mass-limited sample of 97 galaxies at z~1.0-2.6 from ultra-deep spectra obtained during the GMASS spectroscopic survey in the GOODS South field with the Very Large Telescope and FORS2. We obtain robust measures of the rest equivalent width of the Fe II absorption lines down to a limit of W_r_>1.5 {AA} and of the Fe II* emission lines to W_r_>0.5 {AA}. Whenever we can measure the systemic redshift of the galaxies from the [O II] emission line, we find that both the Fe II and Mg II absorption lines are blueshifted, indicating that both species trace gaseous outflows. We also find, however, that the Fe II gas has generally lower outflow velocity relative to that of Mg II. We investigate the variation of Fe II line profiles as a function of the radiative transfer properties of the lines, and find that transitions with higher oscillator strengths are more blueshifted in terms of both line centroids and line wings. We discuss the possibility that Fe II lines are suppressed by stellar absorptions. The lower velocities of the Fe II lines relative to the Mg II doublet, as well as the absence of spatially extended Fe II* emission in two-dimensional stacked spectra, suggest that most clouds responsible for Fe II absorption lie close (3~4 kpc) to the disks of galaxies. We show that the Fe II/Fe II* multiplets offer unique probes of the kinematic structure of galactic outflows.
