- ID:
- ivo://CDS.VizieR/J/A+A/627/A37
- Title:
- Class I disk Oph-IRS 67
- Short Name:
- J/A+A/627/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent results suggest that the first steps towards planet formation may be already taking place in protoplanetary discs during the first 100000yr after stars form. It is therefore crucial to unravel the physical and chemical structures of such discs in their earliest stages while they are still embedded in their natal envelopes and compare them with more evolved systems. The purpose of this paper is to explore the structure of a line-rich Class I protobinary source, Oph-IRS 67, and analyse the differences and similarities with Class 0 and Class II sources. We present a systematic molecular line study of IRS 67 with the Submillimeter Array (SMA) on 1-2" (150-300AU) scales. The wide instantaneous band-width of the SMA observations (~30GHz) provide detections of a range of molecular transitions that trace different physics, such as CO isotopologues, sulphur-bearing species, deuterated species, and carbon-chain molecules. We see significant differences between different groups of species. For example, the CO isotopologues and sulphur-bearing species show a rotational profile and are tracing the larger-scale circumbinary disc structure, while CN, DCN, and carbon-chain molecules peak at the southern edge of the disc at blue-shifted velocities. In addition, the cold gas tracer DCO^+^ is seen beyond the extent of the circumbinary disc. The detected molecular transitions can be grouped into three main components: cold regions far from the system, the circumbinary disc, and a UV-irradiated region likely associated with the surface layers of the disc that are reached by the UV radiation from the sources. The different components are consistent with the temperature structure derived from the ratio of two H_2_CO transitions, that is, warm temperatures are seen towards the outflow direction, lukewarm temperatures are associated with the UV-radiated region, and cold temperatures are related with the circumbinary disc structure. The chemistry towards IRS 67 shares similarities with both Class 0 and Class II sources, possibly due to the high gas column density and the strong UV radiation arising from the binary system. IRS 67 is, therefore, highlighting the intermediate chemistry between deeply embedded sources and T-Tauri discs.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/830/127
- Title:
- CLASSy: CARMA obs. in L1451 region of Perseus
- Short Name:
- J/ApJ/830/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a 3mm spectral line and continuum survey of L1451 in the Perseus Molecular Cloud. These observations are from the CARMA Large Area Star Formation Survey (CLASSy), which also imaged Barnard 1, NGC1333, Serpens Main, and Serpens South. L1451 is the survey region with the lowest level of star formation activity-it contains no confirmed protostars. HCO^+^, HCN, and N_2_H^+^ (J=1->0) are all detected throughout the region, with HCO^+^ being the most spatially widespread, and molecular emission seen toward 90% of the area above N(H_2_) column densities of 1.9x10^21^cm^-2^. HCO^+^ has the broadest velocity dispersion, near 0.3km/s on average, compared with ~0.15km/s for the other molecules, thus representing a range of subsonic to supersonic gas motions. Our non-binary dendrogram analysis reveals that the dense gas traced by each molecule has a similar hierarchical structure, and that gas surrounding the candidate first hydrostatic core (FHSC), L1451-mm, and other previously detected single-dish continuum clumps has similar hierarchical structure; this suggests that different subregions of L1451 are fragmenting on the pathway to forming young stars. We determined that the three-dimensional morphology of the largest detectable dense-gas structures was relatively ellipsoidal compared with other CLASSy regions, which appeared more flattened at the largest scales. A virial analysis shows that the most centrally condensed dust structures are likely unstable against collapse. Additionally, we identify a new spherical, centrally condensed N_2_H^+^ feature that could be a new FHSC candidate. The overall results suggest that L1451 is a young region starting to form its generation of stars within turbulent, hierarchical structures.
- ID:
- ivo://CDS.VizieR/J/ApJ/625/891
- Title:
- Clumps in NGC 7538 at 450 and 850{mu}m
- Short Name:
- J/ApJ/625/891
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present submillimeter continuum maps at 450 and 850{mu}m of a 12'x8' region of the NGC 7538 high-mass star-forming region, made using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. We used an automated clump-finding algorithm to identify 67 clumps in the 450{mu}m image and 77 in the 850{mu}m image.
- ID:
- ivo://CDS.VizieR/J/AJ/136/2083
- Title:
- Clumps in NGC 6334 from 450/850um observations
- Short Name:
- J/AJ/136/2083
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6334 is a galactic star-forming region in Scorpius, heavily obscured by intervening dust. The region consists of several major sites of star formation known previously from far-infrared (IR) and radio-wavelength observations. We present images of NGC 6334 obtained at wavelengths of 850 and 450um with the Submillimeter Common-User Bolometric Array at the James Clerk Maxwell Telescope. These data highlight the distribution of dense cold dust, a particularly striking feature of which is a narrow ridge of emission passing between most of the star-forming centers. We use a clump-finding technique to quantify the distribution of dust emission throughout the region, and we obtain estimates of the sizes, masses, and temperatures of the clump ensemble under simple assumptions.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A131
- Title:
- Clumps in the giant molecular cloud G345.5+1.0
- Short Name:
- J/A+A/534/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive condensations in giant molecular clouds (GMCs) are linked to the formation of high mass stars, which are the principal source of heavy elements and UV radiation, playing an important role in the evolution of galaxies. We attemp to make a complete census of massive-star formation within all of GMC G345.5+1.0. This cloud is located one degree above the Galactic plane and at 1.8kpc from the Sun, thus there is little superposition of dust along the line-of-sight, minimizing confusion effects in identifying individual clumps. GMC G345.5+1.0 is located approximately between 344.5{deg} and 346.5{deg} in Galactic longitude, and between 0.2{deg} and 2.0{deg} in Galactic latitude.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A26
- Title:
- Clumps in W31 from CO and 875um observations
- Short Name:
- J/A+A/531/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-mass star formation has been a very active field over the past decade; however, most studies have targeted regions of luminosities between 10^4^ and 10^5^L_{sun}_. In contrast to that, the highest mass stars reside in clusters exceeding 10^5^ or even 10^6^L_{sun}_. We want to study the physical conditions associated with the formation of the highest mass stars. To do this, we selected the W31 star-forming complex with a total luminosity of ~6x10^6^L_{sun}_ (comprised of at least two subregions) for a multiwavelength spectral line and continuum study covering wavelengths from the near- and midinfrared via (sub)mm wavelength observations to radio data in the cm regime.
- ID:
- ivo://CDS.VizieR/J/ApJS/236/49
- Title:
- CO and 850um obs. of Planck Galactic cold clumps
- Short Name:
- J/ApJS/236/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to understand the initial conditions and early evolution of star formation in a wide range of Galactic environments, we carried out an investigation of 64 Planck Galactic cold clumps (PGCCs) in the second quadrant of the Milky Way. Using the ^13^CO and C^18^O J=1-0 lines and 850{mu}m continuum observations, we investigated cloud fragmentation and evolution associated with star formation. We extracted 468 clumps and 117 cores from the ^13^CO line and 850{mu}m continuum maps, respectively. We made use of the Bayesian distance calculator and derived the distances of all 64 PGCCs. We found that in general, the mass-size plane follows a relation of m~r^1.67^. At a given scale, the masses of our objects are around 1/10 of that of typical Galactic massive star-forming regions. Analysis of the clump and core masses, virial parameters, densities, and mass-size relation suggests that the PGCCs in our sample have a low core formation efficiency (~3.0%), and most PGCCs are likely low-mass star-forming candidates. Statistical study indicates that the 850{mu}m cores are more turbulent, more optically thick, and denser than the ^13^CO clumps for star formation candidates, suggesting that the 850{mu}m cores are likely more appropriate future star formation candidates than the ^13^CO clumps.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A124
- Title:
- CO-CAVITY pilot survey. CO spectra
- Short Name:
- J/A+A/658/A124
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Voids are the most under-dense large-scale regions in the Universe. Galaxies inhabiting voids are one of the keys to understand the intrinsic processes of galaxy evolution, as external factors such as multiple galaxy mergers or a dense self-collapsing environment are negligible. We present the first molecular gas mass survey of void galaxies. We compare these new data, together with data for the atomic gas mass (MHI) and star formation rate (SFR) from the literature to those of galaxies in filaments and walls in order to better understand how molecular gas and star formation are related to the large-scale environment. We observed at the IRAM 30-m telescope the CO(1-0) and CO(2-1) emission of 20 void galaxies selected from the VoidGalaxy Survey (VGS), with a stellar mass range from 108.5to 1010.3M. We detected 15 objects in at least one CO line. We compare the molecular gas mass (MH2), the star formation efficiency (SFE=SFR/MH2), the atomic gas mass, the molecular-to-atomic gas-mass ratio, and the specific star formation rate (sSFR) of the void galaxies with two control samples of galaxies in filaments and walls,selected from xCOLD GASS and EDGE-CALIFA, for different stellar mass bins and taking the star formation activity into account. In general, we do not find any significant differences between void galaxies and the control sample. In particular, we do not find any evidence for a difference in the molecular gas mass or molecular gas mass fraction. Also for the other parameters (SFE,atomic gas mass, molecular-to-atomic gas mass ratio, and sSFR) we find similar (within the errors) mean values between void, and filament and wall galaxies when limiting the sample to star-forming galaxies. We find no evidence for an enhanced sSFR in void galaxies. Some tentative differences emerge when studying trends with stellar mass: The SFE of void galaxies might be lower than in filament and wall galaxies for low stellar masses, and there might be a trend of increasing deficiency in the HI content in void galaxies compared to galaxies in filaments and walls for higher stellar masses, accompanied by an increase in the molecular-to-atomic gas-mass ratio. However, all trends with stellar mass are based on a low number of galaxies and need to be confirmed for a larger sample. The results for the molecular gas mass for a sample of 20 voids galaxies allowed us, for the first time, to make a statistical comparison to galaxies in filaments and walls. We do not find any significant differences of the molecular gas properties and the SFE, but we note that a larger sample is necessary to confirm this and be sensitive to subtle trends.
- ID:
- ivo://CDS.VizieR/J/ApJ/829/93
- Title:
- CO, [CI] and [NII] lines from Herschel spectra
- Short Name:
- J/ApJ/829/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of all CO (J=4-3 through J=13-12), [CI], and [NII] lines available from extragalactic spectra from the Herschel SPIRE Fourier Transform Spectrometer (FTS) archive combined with observations of the low-J CO lines from the literature and from the Arizona Radio Observatory. This work examines the relationships between L_FIR_, L'_CO_, and L_CO_/L_CO,1-0_. We also present a new method for estimating probability distribution functions from marginal signal-to-noise ratio Herschel FTS spectra, which takes into account the instrumental "ringing" and the resulting highly correlated nature of the spectra. The slopes of log(L_FIR_) versus log(L'_CO_) are linear for all mid- to high-J CO lines and slightly sublinear if restricted to (ultra)luminous infrared galaxies ((U)LIRGs). The mid- to high-J CO luminosity relative to CO J=1-0 increases with increasing L_FIR_, indicating higher excitement of the molecular gas, although these ratios do not exceed ~180. For a given bin in L_FIR_, the luminosities relative to CO J=1-0 remain relatively flat from J=6-5 through J=13-12, across three orders of magnitude of L_FIR_. A single component theoretical photodissociation region (PDR) model cannot match these flat SLED shapes, although combinations of PDR models with mechanical heating added qualitatively match the shapes, indicating the need for further comprehensive modeling of the excitation processes of warm molecular gas in nearby galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A144
- Title:
- 13CO (1-0) data molecular cloud catalogue
- Short Name:
- J/A+A/654/A144
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- New-generation spectroscopic surveys of the Milky Way plane have been revealing the structure of the interstellar medium, allowing the simultaneous study of dense structures from single star-forming objects or systems to entire spiral arms. The good sensitivity of the new surveys and the development of dedicated algorithms now enable building extensive catalogues of molecular clouds and deriving good estimates of their physical properties. This allows studying the behaviour of these properties across the Galaxy. We present the catalogue of molecular clouds extracted from the ^13^CO (1-0) data cubes of the Forgotten Quadrant Survey, which mapped the Galactic plane in the range 220{deg}<l<240{deg}, and -2.5{deg}<b<0{deg} in ^12^CO (1-0) and ^13^CO (1-0). We compared the properties of the clouds of our catalogue with those of other catalogues. The catalogue contains 87 molecular clouds for which the main physical parameters such as area, mass, distance, velocity dispersion, and virial parameter were derived. These structures are overall less extended and less massive than the molecular clouds identified in the ^12^CO (1-0) data-set because they trace the brightest and densest part of the ^12^CO (1-0) clouds. Conversely, the distribution of aspect ratio, equivalent spherical radius, velocity dispersion, and virial parameter in the two catalogues are similar. The mean value of the mass surface density of molecular clouds is 87+/-55M_{sun}_/pc^2^ and is almost constant across the galactocentric radius, indicating that this parameter, which is a proxy of star formation, is mostly affected by local conditions. In data of the Forgotten Quadrant Survey, we find a good agreement between the total mass and velocity dispersion of the clouds derived from ^12^CO (1-0) and ^13^CO (1-0). This is likely because in the surveyed portion of the Galactic plane, the H_2_ column density is not particularly high, leading to a CO emission with a not very high optical depth. This mitigates the effects of the different line opacities between the two tracers on the derived physical parameters. This is a common feature in the outer Galaxy, but our result cannot be readily generalised to the entire Milky Way because regions with higher particle density could show a different behaviour.
