- ID:
- ivo://CDS.VizieR/J/ApJS/252/1
- Title:
- OH and HI data in molecular clouds
- Short Name:
- J/ApJS/252/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a OH 18cm survey toward 141 molecular clouds in various environments, including 33 optical dark clouds, 98 Planck Galactic cold clumps (PGCCs), and 10 Spitzer dark clouds with the Arecibo telescope. The deviations from local thermal equilibrium are common for intensity ratios of both OH main lines and satellite lines. Line intensity of OH 1667MHz is found to correlate linearly with visual extinction A_V_ when A_V_ is less than 3mag. It was converted into OH column density by adopting the excitation temperature derived from Monte Carlo simulations with 1{sigma} uncertainty. The relationship between OH abundance X(OH) relative to H_2_ and A_V_ is found to follow an empirical formula, X(OH)/10^-7^=1.3_-0.4_^+0.4^+6.3_-0.5_^+0.5^*exp(-A_V_/2.9_-0.6_^+0.6^). Linear correlation is found between OH and ^13^CO intensity. Besides, nonthermal velocity dispersions of OH and ^13^CO are closely correlated. These results imply tight chemical evolution and spatial occupation between OH and ^13^CO. No obvious correlation is found between column density and nonthermal velocity dispersion of OH and HI narrow self-absorption (HINSA), indicating different chemical evolution and spatial volume occupation between OH and HINSA. Using the age information of HINSA analysis, OH abundance X(OH) is found to increase linearly with cloud age, which is consistent with previous simulations. Fourteen OH components without corresponding CO emission were detected, implying the effectiveness of OH in tracing the "CO-dark" molecular gas.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/582/A118
- Title:
- OH-streamer in SgrA at 1665 and 1667MHz
- Short Name:
- J/A+A/582/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the structure and kinematics of the OH-streamer and the +80km/s cloud and their interactions with the circumnuclear disk (CND) and with other molecular clouds in the vicinity of the Galactic centre (GC), and we map OH absorption at about 6" resolution at R<=10pc from the GC, with about 9km/s of velocity resolution. The VLA was used to map OH line absorption at the 1665 and 1667MHz lambda doublet main lines of the ^2^{PI}_3/2_ state towards the Sagittarius A complex.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A16
- Title:
- OMC 1 reduced H_2_CO(3-2) datacubes
- Short Name:
- J/A+A/609/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We mapped the kinetic temperature structure of the Orion molecular cloud 1 (OMC-1) with para-H_2_CO(J_KaKc_=3_03_-2_02_, 3_22_-2_21_, and 3_21_-2_20_) using the APEX 12m telescope. This is compared with the temperatures derived from the ratio of the NH_3_ (2,2)/(1,1) inversion lines and the dust emission. Using the RADEX non-LTE model, we derive the gas kinetic temperature modeling the measured averaged line ratios of para-H_2_CO 3_22_-2_21_/3_03_-2_02_ and 3_21_-2_20_/3_03_-2_02_. The gas kinetic temperatures derived from the para-H_2_CO line ratios are warm, ranging from 30 to >200K with an average of 62+/-2K at a spatial density of 10^5^cm^-3^. These temperatures are higher than those obtained from NH_3_ (2,2)/(1,1) and CH_3_CCH(6-5) in the OMC-1 region. The gas kinetic temperatures derived from para-H_2_CO agree with those obtained from warm dust components measured in the mid infrared (MIR), which indicates that the para-H_2_CO(3-2) ratios trace dense and warm gas. The cold dust components measured in the far infrared (FIR) are consistent with those measured with NH_3_ (2,2)/(1,1) and the CH_3_CCH(6-5) line series. With dust at MIR wavelengths and para-H_2_CO(3-2) on one side and dust at FIR wavelengths, NH_3_ (2,2)/(1,1), and CH_3_CCH(6-5) on the other, dust and gas temperatures appear to be equivalent in the dense gas (n(H_2_)>~10^4^cm^-3^) of the OMC-1 region, but provide a bimodal distribution, one more directly related to star formation than the other. The non-thermal velocity dispersions of para-H2CO are positively correlated with the gas kinetic temperatures in regions of strong non-thermal motion (Mach number >~2.5) of the OMC-1, implying that the higher temperature traced by para-H2CO is related to turbulence on a ~0.06pc scale. Combining the temperature measurements with para-H_2_CO and NH3 (2,2)/(1,1) line ratios, we find direct evidence for the dense gas along the northern part of the OMC-1 10km/s filament heated by radiation from the central Orion nebula.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A79
- Title:
- ONC stars masses from literature
- Short Name:
- J/A+A/626/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- ALMA observations of the Serpens South star-forming region suggest that stellar protoclusters may be completely mass segregated at birth. Independent observations also suggest that embedded clusters form segregated by mass. As the primordial mass segregation seems to be lost over time, we aim to study on which timescale an initially perfectly mass-segregated star cluster becomes indistinguishable from an initially not mass-segregated cluster. As an example, the Orion Nebula Cluster (ONC) is also discussed. We used N-body simulations of star clusters with various masses and two different degrees of primordial mass segregation. We analysed their energy redistribution through two-body relaxation to quantify the time when the models agree in terms of mass segregation, which sets in only dynamically in the models that are primordially not mass segregated. A comprehensive cross-matched catalogue combining optical, infrared, and X-ray surveys of ONC members was also compiled and made available. The models evolve to a similar radial distribution of high-mass stars after the core collapse (about half a median two-body relaxation time, t_rh_) and become observationally indistinguishable from the point of view of mass segregation at time tau_v_~3.3t_rh_. In the case of the ONC, using the distribution of high-mass stars, we may not rule out either evolutionary scenario (regardless of whether they are initially mass segregated). When we account for extinction and elongation of the ONC, as reported elsewhere, an initially perfectly mass-segregated state seems to be more consistent with the observed cluster.
- ID:
- ivo://CDS.VizieR/J/MNRAS/447/1996
- Title:
- Ophiuchus molecular cloud CO observations
- Short Name:
- J/MNRAS/447/1996
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CO, ^13^CO, and C^18^O J=3-2 observations are presented of the Ophiuchus molecular cloud. The ^13^CO and C^18^O emission is dominated by the Oph A clump, and the Oph B1, B2, C, E, F, and J regions. The optically thin(ner) C18O line is used as a column density tracer, from which the gravitational binding energy is estimated to be 4.5x10^39^J (2282M_{sun}_km^2^/s^2^). The turbulent kinetic energy is 6.3x10^38^J (320M_{sun}_km^2^/s^2^), or seven times less than this, and therefore the Oph cloud as a whole is gravitationally bound. 30 protostars were searched for high-velocity gas, with 8 showing outflows, and 20 more having evidence of high-velocity gas along their lines of sight. The total outflow kinetic energy is 1.3x10^38^J (67M_{sun}_km^2^/s^2^), corresponding to 21 percent of the cloud's turbulent kinetic energy. Although turbulent injection by outflows is significant, but does not appear to be the dominant source of turbulence in the cloud. 10^5^ dense molecular clumplets were identified, which had radii ~0.01-0.05pc, virial masses ~0.1-12M_{sun}_, luminosities ~0.001-0.1K.km/s/pc^2^, and excitation temperatures ~10^-50^K. These are consistent with the standard Giant Molecular Cloud (GMC) based size-linewidth relationships, showing that the scaling laws extend down to size scales of hundredths of a parsec, and to subsolar-mass condensations. There is however no compelling evidence that the majority of clumplets are undergoing free-fall collapse, nor that they are pressure confined.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A29
- Title:
- Optical and near-infrared photometry in Orion A
- Short Name:
- J/A+A/564/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Following the recent discovery a large population of young stars in front of the Orion Nebula we carried out an observational campaign with the DECam wide-field camera covering approximately 10 square degrees centered on NGC 1980 to confirm, probe the extent, and characterize this foreground population of pre-main sequence stars. We used multi-wavelength wide field images and catalogs to identify potential foreground pre-main sequence stars using a novel probabilistic technique based on a careful selection of colors and luminosities. We confirmed the presence of a large foreground population towards the Orion A cloud. This population contains several distinct sub-groups including NGC 1980 and NGC 1981 and stretches over several degrees in front of the Orion A cloud. By comparing the location of their sequence in various color-magnitude diagrams to other clusters, we found a distance and an age of 380pc and 5 to 10Myr, in good agreement with previous estimates. Our final sample includes 2123 candidate members and is complete from below the hydrogen burning limit to about 0.3M_{sun}_ where the data starts to be limited by saturation. Extrapolating the mass function to the high masses, we estimated a total number of ~2600 members in the surveyed region.
- ID:
- ivo://CDS.VizieR/J/ApJ/680/1295
- Title:
- Optical spectroscopy of Cha-II PMS stars
- Short Name:
- J/ApJ/680/1295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the results of the optical spectroscopic follow-up of pre-main-sequence (PMS) objects and candidates selected in the Chamaeleon II dark cloud based on data from the Spitzer Legacy survey "From Molecular Cores to Planet Forming Disks" (c2d) and from previous surveys. Our sample includes both objects with infrared excess selected according to c2d criteria and referred to as young stellar objects and other cloud members and candidates selected from complementary optical and near-infrared data. We characterize the sample of objects by deriving their physical parameters.
- ID:
- ivo://CDS.VizieR/J/ApJ/844/138
- Title:
- Optical spectroscopy toward Orion B fields
- Short Name:
- J/ApJ/844/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from high-resolution optical spectra toward 66 young stars in the Orion B molecular cloud to study their kinematics and other properties. Observations of the H{alpha} and Li I 6707{AA} lines are used to check membership and accretion properties. While the stellar radial velocities of NGC 2068 and L1622 are in good agreement with that of the molecular gas, many of the stars in NGC 2024 show a considerable offset. This could be a signature of either the expansion of the cluster, the high degree of the ejection of the stars from the cluster through dynamical interaction, or the acceleration of the gas due to stellar feedback.
- ID:
- ivo://CDS.VizieR/J/A+A/455/971
- Title:
- Organic molecules in the Galactic center
- Short Name:
- J/A+A/455/971
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out a systematic study of the complex organic molecules CH_3_OH, C_2_H_5_OH, (CH_3_)_2_O, HCOOCH_3_, HCOOH, CH_3_COOH, H_2_CO, and CS toward 40 GC molecular clouds. Using the LTE approximation, we derived the physical properties of GC molecular clouds and the abundances of the complex molecules.The abundances of complex organic molecules in the GC are compared with those measured in hot cores and hot corinos, in which these complex molecules are also abundant.
- ID:
- ivo://CDS.VizieR/J/ApJS/217/7
- Title:
- Orion A dense cores based on 1.1mm and C^18^O
- Short Name:
- J/ApJS/217/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Orion A giant molecular cloud core catalogs, which are based on a 1.1mm map with an angular resolution of 36" (~0.07pc) and C^18^O (J=1-0) data with an angular resolution of 26.4" (~0.05pc). We have cataloged 619 dust cores in the 1.1mm map using the Clumpfind method. The ranges of the radius, mass, and density of these cores are estimated to be 0.01-0.20pc, 0.6-1.2x10^2^M_{sun}_ , and 0.3x10^4^-9.2x10^6^cm^-3^, respectively. We have identified 235 cores from the C^18^O data. The ranges of the radius, velocity width, LTE mass, and density are 0.13-0.34pc, 0.31-1.31km/s, 1.0-61.8M_{sun}_ , and (0.8-17.5)x10^3^cm^-3^, respectively. From the comparison of the spatial distributions between the dust and C^18^O cores, four types of spatial relations were revealed: (1) the peak positions of the dust and C^18^O cores agree with each other (32.4% of the C^18^O cores), (2) two or more C^18^O cores are distributed around the peak position of one dust core (10.8% of the C^18^O cores), (3) 56.8% of the C^18^O cores are not associated with any dust cores, and (4) 69.3% of the dust cores are not associated with any C^18^O cores.
