- ID:
- ivo://CDS.VizieR/J/A+A/658/A160
- Title:
- SEDIGISM survey, search for molecular outflows
- Short Name:
- J/A+A/658/A160
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The formation processes of massive stars are still unclear but a picture is emerging involving accretion disks and molecular outflows in what appears to be a scaled-up version of lower-mass star formation. A census of outflow activity towards high-mass star-forming clumps in various evolutionary stages has the potential to shed light on high-mass star formation. We conduct an outflow survey toward ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) clumps, using SEDIGISM (structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium) data and aim to obtain a large sample of clumps exhibiting outflow activity in different evolutionary stages. We identify the high-velocity wings of the ^13^CO lines, indicating outflow activity, toward ATLASGAL clumps by (1) extracting the simultaneously observed ^13^CO(2-1) and C^18^O(2-1) spectra from SEDIGISM, and (2) subtracting the scaled C^18^O (cores emission) from the ^13^CO, after considering opacity broadening. We have detected high-velocity gas towards 1192 clumps out of a total sample of 2052 corresponding to an overall detection rate of 58%. Outflow activity has been detected from the earliest (apparently) quiescent clumps (i.e., 70 microns weak), to the most evolved HII region stages (i.e., 8 micron bright with tracers of massive star formation). The detection rate increases as a function of evolution (quiescent = 51%, protostellar = 47%, YSO = 57%, UCHII regions = 76%). Our sample is the largest outflow sample identified so far. The high detection rate from this large sample is consistent with the results of similar studies reported in the literature and supports the scenario that outflows are a ubiquitous feature of high-mass star formation. The lower detection rate in early evolutionary stages could be due to the fact that outflows in the early stages are weak and difficult to detect. We obtain a statistically significant number of outflow clumps for every evolutionary stage, especially for outflow clumps in the earliest stages (i.e., 70 microns dark cloud or massive starless core).
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/620/A62
- Title:
- Serpens filament emission lines datacubes
- Short Name:
- J/A+A/620/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Serpens filament, as one of the nearest infrared dark clouds, is regarded as a pristine filament at a very early evolutionary stage of star formation. In order to study its molecular content and dynamical state, we mapped this filament in seven species including C^18^O, HCO^+^, HNC, HCN, N_2_H^+^, CS, and CH_3_OH. Among them, HCO^+^, HNC, HCN, and CS show self-absorption, while C^18^O is most sensitive to the filamentary structure. A kinematic analysis demonstrates that this filament forms a velocity-coherent (trans-)sonic structure, a large part of which is one of the most quiescent regions in the Serpens cloud. Widespread C^18^O depletion is found throughout the Serpens filament. Based on the Herschel dust-derived H_2_ column density map, the line mass of the filament is 36-41~M_{sun}_/pc, and its full width at half maximum width is 0.17+/-0.01pc, while its length is ~1.6pc. The inner radial column density profile of this filament can be well fitted with a Plummer profile with an exponent of 2.2+/-0.1, a scale radius of 0.018+/-0.003pc and a central density of (4.0+/-0.8)x10^4^cm^-3^. The Serpens filament appears to be slightly supercritical. The widespread blue-skewed HNC and CS line profiles and HCN hyperfine line anomalies across this filament indicate radial infall in parts of the Serpens filament. C^18^O velocity gradients also indicate accretion flows along the filament. The velocity and density structures suggest that such accretion flows are likely due to a longitudinal collapse parallel to the filament's long axis. Both the radial infall rate and the longitudinal accretion rate along the Serpens filament are lower than all previously reported values in other filaments. This indicates that the Serpens filament lies at an early evolutionary stage when collapse has just begun, or that thermal and non-thermal support are effective in providing support against gravity.
- ID:
- ivo://CDS.VizieR/J/ApJS/192/15
- Title:
- Seven-year WMAP catalog
- Short Name:
- J/ApJS/192/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present updated estimates of Galactic foreground emission using seven years of WMAP data. Using the power spectrum of differences between multi-frequency template-cleaned maps, we find no evidence for foreground contamination outside of the updated (KQ85y7) foreground mask. We place a 15uK upper bound on rms foreground contamination in the cleaned maps used for cosmological analysis. Further, the cleaning process requires only three power-law foregrounds outside of the mask. We find no evidence for polarized foregrounds beyond those from soft (steep-spectrum) synchrotron and thermal dust emission; in particular we find no indication in the polarization data of an extra "haze" of hard synchrotron emission from energetic electrons near the Galactic center. We provide an updated map of the cosmic microwave background (CMB) using the internal linear combination method, updated foreground masks, and updates to point source catalogs using two different techniques. With additional years of data, we now detect 471 point sources using a five-band technique and 417 sources using a three-band CMB-free technique. In total there are 62 newly detected point sources, a 12% increase over the five-year release.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A6
- Title:
- SgrB2 ALMA continuum and spectral index
- Short Name:
- J/A+A/604/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The two hot molecular cores SgrB2(M) and SgrB2(N), which are located at the center of the giant molecular cloud complex Sagittarius B2, have been the targets of numerous spectral line surveys, revealing a rich and complex chemistry. We seek to characterize the physical and chemical structure of the two high-mass star-forming sites SgrB2(M) and SgrB2(N) using high-angular resolution observations at millimeter wavelengths, reaching spatial scales of about 4000au. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to perform an unbiased spectral line survey of both regions in the ALMA band 6 with a frequency coverage from 211GHz to 275GHz. The achieved angular resolution is 0.4-arcsec, which probes spatial scales of about 4000au, i.e., able to resolve different cores and fragments. In order to determine the continuum emission in these line-rich sources, we used a new statistical method, STATCONT, which has been applied successfully to this and other ALMA datasets and to synthetic observations. We detect 27 continuum sources in SgrB2(M) and 20 sources in SgrB2(N). We study the continuum emission variation across the ALMA band 6 (i.e., spectral index) and compare the ALMA 1.3mm continuum emission with previous SMA 345GHz and VLA 40GHz observations to study the nature of the sources detected. The brightest sources are dominated by (partially optically thick) dust emission, while there is an important degree of contamination from ionized gas free-free emission in weaker sources. While the total mass in SgrB2(M) is distributed in many fragments, most of the mass in SgrB2(N) arises from a single object, with filamentary-like structures converging toward the center. There seems to be a lack of low-mass dense cores in both regions. We determine H2 volume densities for the cores of about 10^7^-10^9^cm^-3^ (or 10^5^-10^7^M_{sun}_/pc^3^), i.e., one to two orders of magnitude higher than the stellar densities of super star clusters. We perform a statistical study of the chemical content of the identified sources. In general, SgrB2(N) is chemically richer than SgrB2(M). The chemically richest sources have about 100 lines per GHz and the fraction of luminosity contained in spectral lines at millimeter wavelengths with respect to the total luminosity is about 20%-40%. There seems to be a correlation between the chemical richness and the mass of the fragments, where more massive clumps are more chemically rich. Both SgrB2(N) and SgrB2(M) harbor a cluster of hot molecular cores. We compare the continuum images with predictions from a detailed 3D radiative transfer model that reproduces the structure of SgrB2 from 45pc down to 100au. This ALMA dataset, together with other ongoing observational projects in the range 5GHz to 200GHz, better constrain the 3D structure of SgrB2 and allow us to understand its physical and chemical structure.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A32
- Title:
- Sgr B2 Herschel/SPIRE-FTS and IRAM 30m maps
- Short Name:
- J/A+A/649/A32
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present 168 arcmin^2^ spectral images of the Sgr B2 complex taken with Herschel/SPIRE-FTS. We detect ubiquitous emission from CO (up to J=12-11), H2O 2_1,1_-2_0,2_, [CI]492, 809GHz, and [NII] 205um lines. We also present maps of the SiO, N_2_H^+^, HCN, and HCO^+^ emission obtained with the IRAM30m telescope. The cloud environment dominates the emitted FIR (80%), H_2_O 752GHz (60%) mid-J CO (91%), and [CI] (93%) luminosity. The region shows very extended [NII] emission (spatially correlated with the 24 and 70um dust emission). The observed FIR luminosities imply G_0_~10^3^. The extended [CI] emission arises from a pervasive component of neutral gas with n_H_~10^3cm^-3^. The high ionization rates, produced by enhanced cosmic-ray (CR) fluxes, drive the gas heating to T_k_~40-60K. The mid-J CO emission arises from a similarly extended but more pressurized gas component (P_th_/k~10^7^K/cm^3^). Specific regions of enhanced SiO emission and high CO-to-FIR intensity ratios (>10^-3^) show mid-J CO emission compatible with shock models. A major difference compared to more quiescent star-forming clouds in the disk of our Galaxy is the extended nature of the SiO and N_2_H^+^ emission in Sgr B2. This can be explained by the presence of cloud-scale shocks, induced by cloud-cloud collisions and stellar feedback, and the much higher CR ionization rate (>10^-15^s^-1^) leading to overabundant H_3_^+^ and N_2_H^+^. Hence, Sgr B2 hosts a more extreme environment than star-forming regions in the disk of the Galaxy. As a usual template for extra- galactic comparisons, Sgr B2 shows more similarities to ultra luminous infrared galaxies such as Arp 220, including a "deficit" in the [CI]/FIR and [NII]/FIR intensity ratios, than to pure starburst galaxies such as M82. However, it is the extended cloud environment, rather than the cores, that serves as a useful template when telescopes do not resolve such extended regions in galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A10
- Title:
- Sgr B2 los molecular absorption line spectra
- Short Name:
- J/A+A/610/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 1-50 GHz PRebiotic Interstellar MOlecular Survey (PRIMOS) contains >50 molecular absorption lines observed in clouds located in the line-of-sight to Sgr B2(N). The line-of- sight material is associated with diffuse and translucent clouds located in the Galactic Center, Bar, and spiral arms in the disk. We measure the column densities and estimate abundances, relative to H_2_, of 11 molecules and additional isotopologues observed in this material. We use absorption by optically thin transitions of c-C_3_H_2_ to estimate the molecular hydrogen columns, and argue that this method is preferable to more commonly used methods. We discuss the kinematic structure and abundance patterns of small molecules including the sulfur-bearing species CS, SO, CCS, H_2_CS, and HCS+; oxygen-bearing molecules OH, SiO, and H_2_CO; and simple hydrocarbon molecules c-C_3_H_2_, l-C_3_H, and l-C_3_H^+^. Finally, we discuss the implications of the observed chemistry for the structure of the gas and dust in the ISM. Highlighted results include the following. First, whereas gas in the disk has a molecular hydrogen fraction of 0.65, clouds on the outer edge of the Galactic Bar and in or near the Galactic Center have molecular fractions of 0.85 and >0.9, respectively. Second, we observe trends in isotope ratios with Galactocentric distance; while carbon and silicon show enhancement of the rare isotopes at low Galactocentric distances, sulfur exhibits no trend with Galactocentric distance. We also determine that the ratio of c-C_3_H_2_/c-H^13^CCCH provides a good estimate of the ^12^C/^13^C ratio, whereas H_2_CO/H_2_(^13^C)O exhibits fractionation. Third, we report the presence of l-C_3_H^+^ in diffuse clouds for the first time. Finally, we suggest that CS has an enhanced abundance within higher density clumps of material in the disk, and therefore may be diagnostic of cloud conditions. If this holds, the diffuse clouds in the Galactic disk contain multiple embedded hyperdensities in a clumpy structure, and the density profile is not a simple function of A_V_.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A120
- Title:
- SgrB2(M) ^13^CCC and C^13^CC spectra
- Short Name:
- J/A+A/633/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon molecules and their ^13^C-isotopologues can be used to determine the ^12^C/^13^C abundance ratios in stellar and interstellar objects. C3 is a pure carbon chain molecule found in star forming regions and in stellar shells of carbon-rich late-type stars. Latest laboratory data of ^13^C-isotopologues of C3 allow a selective search for the mono-substituted species ^13^CCC and C^13^CC based on accurate ro-vibrational frequencies. Our aim was to provide the first detection of the ^13^C-isotopologues ^13CCC and C^13^CC in space and to derive the ^12^C/ ^13^C ratio of interstellar gas in the massive star-forming region SgrB2(M) near the Galactic Center. We used the heterodyne receivers GREAT and upGREAT on board SOFIA to search for the ro-vibrational transitions Q(2) and Q(4) of ^13^CCC and C^13^CC at 1.9THz along the line of sight towards SgrB2(M). In addition, to determine the local excitation temperature we analyzed data from nine ro-vibrational transitions of the main isotopologue CCC in the frequency range between 1.6-1.9THz which were taken from the Herschel Science Data Archive. We report the first detection of the isotopologues ^13^CCC and C^13^CC. For both species the ro-vibrational absorption lines Q(2) and Q(4) have been identified, primarily arising from the warm gas physically associated with the strong continuum source SgrB2(M). From the available CCC ro-vibrational transitions we derived a gas excitation temperature of Tex=44.4^+4.7^_-3.9_K and a total column density of N(CCC)=3.88^+0.39^_-0.35_x10^15^cm^-2.. Assuming the excitation temperatures of C^13^CC and ^13^CCC to be the same as for CCC, we obtained column densities of the ^13^C-isotopologues of N(C^13^CC)=2.1^+0.9^_-0.6^_x10^14^cm^-2^ and N(^13^CCC)=2.4^+1.2^_-0.8_x10^14^cm^-2^. The derived ^12^C/^13^C abundance ratio in the C3 molecules is 20.5+/-4.2, which is in agreement with the elemental ratio of 20, typically observed in SgrB2(M). However, we find the N(^13^CCC)/N(C^13^CC) ratio to be 1.2+/-0.1, which is shifted from the statistically expected value of 2. We propose that the discrepant abundance ratio arises due to the the lower zero-point energy of C^13^CC which makes position- exchange reaction converting C^13^CC to C^13^CC energetically favorable.
- ID:
- ivo://CDS.VizieR/J/ApJS/117/427
- Title:
- Sgr B2 spectral survey
- Short Name:
- J/ApJS/117/427
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have surveyed the frequency band 218.30-263.55GHz toward the core positions N and M and the quiescent cloud position NW in the Sgr B2 molecular cloud using the Swedish-ESO Submillimetre Telescope. In total 1730, 660, and 110 lines were detected in N, M, and NW, respectively, and 42 different molecular species were identified. The number of unidentified lines are 337, 51, and eight. Toward the N source, spectral line emission constitutes 22% of the total detected flux in the observed band, and complex organic molecules are the main contributors. Toward M, 14% of the broadband flux is caused by lines, and SO2 is here the dominant source of emission. NW is relatively poor in spectral lines and continuum. In this paper we present the spectra together with tables of suggested line identifications.
- ID:
- ivo://CDS.VizieR/J/AJ/151/143
- Title:
- Silicon depletion in the interstellar medium
- Short Name:
- J/AJ/151/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report interstellar silicon (Si) depletion and dust-phase column densities of Si along 131 Galactic sight lines using archival observations. The data were corrected for differences in the assumed oscillator strength. This is a much larger sample than previous studies but confirms the majority of results, which state that the depletion of Si is correlated with the average density of hydrogen along the line of sight (<n(H)>) as well as the fraction of hydrogen in molecular form (f(H_2_)). We also find that the linear part of the extinction curve is independent of Si depletion. Si depletion is correlated with the bump strength (c_3_/R_V_) and the FUV curvature (c_4_/R_V_) suggesting that silicon plays a significant role in both the 2175{AA} bump and the FUV rise.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A16
- Title:
- Silicon K-edge dust absorption cross sections
- Short Name:
- J/A+A/627/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The composition and properties of interstellar silicate dust are not well understood. Inthe X-rays, interstellar dust can be studied in detail, by making use of the fine structure features inthe Si K-edge. The features in the Si K-edge offer a range of possibilities to study silicon-bearingdust, such as investigating the crystallinity, abundance and the chemical composition along a given line of sight. We present newly acquired laboratory measurements of the silicon K-edge of several silicate-compounds which complement our measurements from our earlier pilot study. The resulting dust extinction profiles serve as templates for the interstellar extinction that we observe. The extinction profiles were used to model the interstellar dust in the dense environments of the Galaxy. The laboratory measurements, taken at the Soleil synchrotron facility in Paris, were adapted for astrophysical data analysis and implemented in the SPEX spectral fitting program. The models were used to fit the spectra of nine low-mass X-ray binaries located in the Galactic center neighborhood in order to determine the dust properties along those lines of sight. In most lines of sight can be well fitted by amorphous olivine. We also established upper limits on the amount of crystalline material that the modeling allows. We obtained values of the total silicon abundance, silicon dust abundance and depletion along each of the sightlines. We find a possible gradient of 0.06+/-0.02dex/kpc for the total silicon abundance versus the Galactocentric distance. We do not find a relation between the depletion and the extinction along the line of sight.
