- ID:
- ivo://CDS.VizieR/J/ApJ/732/101
- Title:
- C^18^O cores in the S140 cloud
- Short Name:
- J/ApJ/732/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of C^18^O(J=1-0) mapping observations of a 20'x18' area in the Lynds 1204 molecular cloud associated with the Sharpless 2-140 (S140) HII region. The C^18^O cube ({alpha}-{delta}-{nu}_LSR_) data show that there are three clumps of sizes ~1pc in the region. Two of these have peculiar redshifted velocity components at their edges, which can be interpreted as the results of the interaction between the cloud and the Cepheus Bubble. From the C^18^O cube data, clumpfind identified 123 C^18^O cores, which have mean radius, velocity width in FWHM, and LTE mass of 0.36+/-0.07pc, 0.37+/-0.09km/s, and 41+/-29M_{sun}_, respectively. Considering the uncertainty in the C^18^O abundance, all the cores in S140 are most likely to be gravitationally bound. We derived a C^18^O core mass function (CMF), which shows a power-law-like behavior above a turnover at 30M_{sun}_.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/760/147
- Title:
- ^13^CO cores in the Taurus molecular cloud
- Short Name:
- J/ApJ/760/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young stars form in molecular cores, which are dense condensations within molecular clouds. We have searched for molecular cores traced by ^13^CO J=1-->0 emission in the Taurus molecular cloud and studied their properties. Our data set has a spatial dynamic range (the ratio of linear map size to the pixel size) of about 1000 and spectrally resolved velocity information, which together allow a systematic examination of the distribution and dynamic state of ^13^CO cores in a large contiguous region. We use empirical fit to the CO and CO_2_ ice to correct for depletion of gas-phase CO. The ^13^CO core mass function (^13^CO CMF) can be fitted better with a log-normal function than with a power-law function. We also extract cores and calculate the ^13^CO CMF based on the integrated intensity of ^13^CO and the CMF from Two Micron All Sky Survey. We demonstrate that core blending exists, i.e., combined structures that are incoherent in velocity but continuous in column density. The core velocity dispersion (CVD), which is the variance of the core velocity difference {delta}v, exhibits a power-law behavior as a function of the apparent separation L: CVD(km/s){prop.to}L(pc)^0.7^. This is similar to Larson's law for the velocity dispersion of the gas. The peak velocities of ^13^CO cores do not deviate from the centroid velocities of the ambient ^12^CO gas by more than half of the line width. The low velocity dispersion among cores, the close similarity between CVD and Larson's law, and the small separation between core centroid velocities and the ambient gas all suggest that molecular cores condense out of the diffuse gas without additional energy from star formation or significant impact from converging flows.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A154
- Title:
- CO datacube abd spectra of UGC 10214
- Short Name:
- J/A+A/623/A154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Minor mergers play a crucial role in galaxy evolution. UGC 10214 (the Tadpole galaxy) is a prime example of this process in which a dwarf galaxy has interacted with a large spiral galaxy ~250 Myr ago and produced a perturbed disc and a giant tidal tail. We used a multi-wavelength dataset that partly consists of new observations (H{alpha}, HI, and CO) and partly of archival data to study the present and past star formation rate (SFR) and its relation to the gas and stellar mass at a spatial resolution down to 4 kpc. UGC 10214 is a high-mass (stellar mass M_*_=1.28x10^11^ M_{sun}_) galaxy with a low gas fraction (M_gas_/M_*_=0.24), a high molecular gas fraction (M_H2_/M_HI_=0.4), and a modest SFR (2-5 M_{sun}_/yr). The global SFR compared to its stellar mass places UGC 10214 on the galaxy main sequence (MS). The comparison of the molecular gas mass and current SFR gives a molecular gas depletion time of about ~2 Gyr (based on H{alpha}), comparable to those of normal spiral galaxies. Both from a comparison of the H{alpha} emission, tracing the current SFR, and far-ultraviolet (FUV) emission, tracing the recent SFR during the past tens of Myr, and also from spectral energy distribution fitting with CIGALE, we find that the SFR has increased by a factor of about 2-3 during the recent past. This increase is particularly noticeable in the centre of the galaxy where a pronounced peak of the H{alpha} emission is visible. A pixel-to-pixel comparison of the SFR, molecular gas mass, and stellar mass shows that the central region has had a depressed FUV-traced SFR compared to the molecular gas and the stellar mass, whereas the H{alpha}-traced SFR shows a normal level. The atomic and molecular gas distribution is asymmetric, but the position-velocity diagram along the major axis shows a pattern of regular rotation. We conclude that the minor merger has most likely caused variations in the SFR in the past that resulted in a moderate increase of the SFR, but it has not perturbed the gas significantly so that the molecular depletion time remains normal.
- ID:
- ivo://CDS.VizieR/J/A+A/648/A41
- Title:
- 12CO(2-1) datacubes of 3 IR sources
- Short Name:
- J/A+A/648/A41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Lupus star-forming complex includes some of the closest low-mass star-forming regions, and together they house objects that span evolutionary stages from pre-stellar to pre-MS. By studying 7 objects in the Lupus clouds from prestellar to protostellar stages, we aim to test if a coherence exists between commonly used evolutionary tracers. We present ALMA observations of the 1.3mm continuum and molecular line emission that probe the dense gas and dust of cores (continuum, C^18^O, N_2_D^+^) and their associated molecular outflows (^12^CO). Our selection of sources in a common environment, with identical observing strategy, allows for a consistent comparison across different evolutionary stages. We complement our study with continuum and line emission from the ALMA archive in different bands. The quality of the ALMA molecular data allows us to reveal the nature of the molecular outflows in the sample by studying their morphology and kinematics, through interferometric mosaics covering their full extent. The interferometric images in IRAS 15398-3359 appear to show that it drives a precessing episodic jet-driven outflow with at least 4 ejections separated by periods of time between 50 and 80 years, while data in IRAS 16059-3857 show similarities with a wide-angle wind model also showing signs of being episodic. The outflow of J160115-41523 could be better explain with the wide-angle wind model as well, but new observations are needed to further explore its nature. We find that the most common evolutionary tracers in the literature are useful for broad evolutionary classifications, but are not consistent with each other to provide enough granularity to disentangle different evolutionary stage of sources that belong to the same Class (0, I, II, or III). The evolutionary classification revealed by our analysis coincides with those determined by previous studies for all our sources except J160115-41523. Outflow properties used as protostellar age tracers, such as mass, momentum, energy and opening angle, may suer from differences in the nature of each outflow, and therefore detailed observations are needed to refine evolutionary classifications. We found both AzTEC-lup1-2 and AzTEC-lup3-5 to be in the pre-stellar stage, with the possibility that the latter is a more evolved source. IRAS 15398-3359, IRAS 16059-3857 and J160115-41523, which have clearly detected outflows, are Class 0 sources, although we are not able to determine which is younger and which is older. Finally Sz 102 and Merin 28 are the most evolved sources in our sample and show signs of having associated flows, not as well traced by CO as for the younger sources.
- ID:
- ivo://CDS.VizieR/J/A+A/594/A117
- Title:
- CO-H2 and complex organic molecules in TMC-1C
- Short Name:
- J/A+A/594/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Almost 200 different species have been detected in the interstellar medium (ISM) during the last decades, revealing not only simple species but complex molecules with more than 6 atoms. Other exotic compounds, like the weakly-bound dimer (H_2_)_2_, have also been detected in astronomical sources like Jupiter. We aim at detecting for the first time the CO-H_2_ van der Waals complex in the ISM, which if detected can be a sensitive indicator for low temperatures. We use the IRAM30m telescope, located in Pico Veleta (Spain), to search for the CO-H_2_ complex in a cold, dense core in TMC-1C (with a temperature of 10K). All the brightest CO-H_2_ transitions in the 3mm (80-110GHz) band have been observed with a spectral resolution of 0.5-0.7km/s, reaching a rms noise level of 2mK. The simultaneous observation of a broad frequency band, 16GHz, has allowed us to conduct a serendipitous spectral line survey. No lines belonging to the CO-H_2_ complex have been detected. We have set up a new, more stringent upper limit for its abundance to be [CO-H_2_]/[CO]=5x10^-6^, while we expect the abundance of the complex to be in the range 10^-8^-10^-3^. The spectral line survey has allowed us to detect 75 lines associated with 41 different species (including isotopologues). We detect a number of complex organic species, e.g. methyl cyanide (CH_3_CN), methanol (CH_3_OH), propyne (CH_3_CCH) and ketene (CH_2_CO), associated with cold gas (excitation temperatures about 7K), confirming the presence of these complex species not only in warm objects but also in cold regimes.
- ID:
- ivo://CDS.VizieR/J/ApJS/181/255
- Title:
- CO in Galactic HII regions
- Short Name:
- J/ApJS/181/255
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the molecular properties for a sample of 301 Galactic HII regions including 123 ultra compact (UC), 105 compact, and 73 diffuse nebulae. We analyze all sources within the BU-FCRAO Galactic Ring Survey (GRS) of ^13^CO emission known to be HII regions based upon the presence of radio continuum and cm-wavelength radio recombination line emission. Unlike all previous large area coverage ^13^CO surveys, the GRS is fully sampled in angle and yet covers ~75deg^2^ of the Inner Galaxy. The angular resolution of the GRS (46") allows us to associate molecular gas with HII regions without ambiguity and to investigate the physical properties of this molecular gas. We find clear CO/HII morphological associations in position and velocity for ~80% of the nebular sample. Compact HII region molecular gas clouds are on average larger than UC clouds: 2.2' compared to 1.7'.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/174
- Title:
- CO in Protostars (COPS): Herschel spectroscopy
- Short Name:
- J/ApJ/860/174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present full spectral scans from 200 to 670{mu}m of 26 Class 0+I protostellar sources obtained with Herschel-SPIRE as part of the "COPS-SPIRE" Open Time program, complementary to the DIGIT and WISH Key Programs. Based on our nearly continuous, line-free spectra from 200 to 670{mu}m, the calculated bolometric luminosities (Lbol) increase by 50% on average, and the bolometric temperatures (Tbol) decrease by 10% on average, in comparison with the measurements without Herschel. Fifteen protostars have the same class using Tbol and Lbol/Lsmm. We identify rotational transitions of CO lines from J=4->3 to J=13->12, along with emission lines of ^13^CO, HCO^+^, H_2_O, and [CI]. The ratios of ^12^CO to ^13^CO indicate that ^12^CO emission remains optically thick for J_up_<13. We fit up to four components of temperature from the rotational diagram with flexible break points to separate the components. The distribution of rotational temperatures shows a primary population around 100K with a secondary population at ~350K. We quantify the correlations of each line pair found in our data set and find that the strength of the correlation of CO lines decreases as the difference between J levels between two CO lines increases. The multiple origins of CO emission previously revealed by velocity-resolved profiles are consistent with this smooth distribution if each physical component contributes to a wide range of CO lines with significant overlap in the CO ladder. We investigate the spatial extent of CO emission and find that the morphology is more centrally peaked and less bipolar at high-J lines. We find the CO emission observed with SPIRE related to outflows, which consists of two components, the entrained gas and shocked gas, as revealed by our rotational diagram analysis, as well as the studies with velocity-resolved CO emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/49
- Title:
- CO large-field observations around l=150{deg}
- Short Name:
- J/ApJ/838/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present large-field (4.25x3.75deg^2^) mapping observations toward the Galactic region centered at l=150{deg},b=3.5{deg} in the J=1-0 emission line of CO isotopologues (^12^CO, ^13^CO, and C^18^O), using the 13.7m millimeter-wavelength telescope of the Purple Mountain Observatory. Based on the ^13^CO observations, we reveal a filamentary cloud in the Local Arm at a velocity range of -0.5 to 6.5km/s. This molecular cloud contains 1 main filament and 11 sub-filaments, showing the so-called "ridge-nest" structure. The main filament and three sub-filaments are also detected in the C^18^O line. The velocity structures of most identified filaments display continuous distribution with slight velocity gradients. The measured median excitation temperature, line width, length, width, and linear mass of the filaments are ~9.28K, 0.85km/s, 7.30pc, 0.79pc, and 17.92M_{sun}_/pc, respectively, assuming a distance of 400pc. We find that the four filaments detected in the C^18^O line are thermally supercritical, and two of them are in the virialized state, and thus tend to be gravitationally bound. We identify in total 146 ^13^CO clumps in the cloud, about 77% of the clumps are distributed along the filaments. About 56% of the virialized clumps are found to be associated with the supercritical filaments. Three young stellar object candidates are also identified in the supercritical filaments, based on the complementary infrared data. These results indicate that the supercritical filaments, especially the virialized filaments, may contain star-forming activities.
139. Cold galaxies
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/2050
- Title:
- Cold galaxies
- Short Name:
- J/MNRAS/453/2050
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use 350 {mu}m angular diameter estimates from Planck to test the idea that some galaxies contain exceptionally cold (10-13 K) dust, since colder dust implies a lower surface brightness radiation field illuminating the dust, and hence a greater physical extent for a given luminosity. The galaxies identified from their spectral energy distributions as containing cold dust do indeed show the expected larger 350 {mu}m diameters. For a few cold dust galaxies where Herschel data are available, we are able to use submillimetre maps or surface brightness profiles to locate the cold dust, which as expected generally lies outside the optical galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/639/A26
- Title:
- Cold HI, H2 and total H column density FITS maps
- Short Name:
- J/A+A/639/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There are significant amounts of H_2_ in the Milky Way. Due to its symmetry H_2_ does not radiate at radio frequencies. CO is thought to be a tracer for H_2_, however CO is formed at significantly higher opacities than H_2_. Thus, toward high Galactic latitudes significant amounts of H_2_ are hidden and called CO-dark. We demonstrate that the dust-to-gas ratio is a tool to identify locations and column densities of CO-dark H_2_. We adopt the hypothesis of a constant E(B-V)/NH ratio, independent of phase transitions from HI to H_2_. We investigate the Doppler temperatures T_D_, from a Gaussian decomposition of HI4PI data, to study temperature dependencies of E(B-V)/NHI. The E(B-V)/NHI ratio in the cold HI gas phase is high in comparison to the warmer one. We consider this as evidence that cold HI gas toward high Galactic latitudes is associated with H_2_. Beyond CO-bright regions we find for T_D_<1165K a correlation (NHI+2NH_2_)/NHI{prop.to}-log T_D_. In combination with a factor XCO=4.0x10^20^cm^-2^(K.km/s)^-1^ this yields for the full-sky NH/E(B-V)~5.1 to 6.7 10^21^cm^-2^mag^-1^, compatible with X-ray scattering and UV absorption line observations. Cold HI with T_D_<1165K contains on average 46% CO-dark H_2_. Prominent filaments have T_D_<220K and typical excitation temperatures Tex~50K. With a molecular gas fraction of >61% they are dominated dynamically by H_2_.
