- ID:
- ivo://CDS.VizieR/J/ApJ/696/298
- Title:
- Dense cores in Perseus
- Short Name:
- J/ApJ/696/298
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the chemistry, temperature, and dynamical state of a sample of 193 dense cores or core candidates in the Perseus Molecular cloud and compare the properties of cores associated with young stars and clusters with those which are not. The combination of our NH3 and CCS observations with previous millimeter, submillimeter, and Spitzer data available for this cloud enables us both to determine core properties precisely and to accurately classify cores as starless or protostellar.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/691/1560
- Title:
- Dense core survey in the Orion B cloud
- Short Name:
- J/ApJ/691/1560
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out an H^13^CO^+^(J=1-0 at 86.75433GHz) core survey in a large area of 1deg^2^, covering most of the dense region in the Orion B molecular cloud, using the Nobeyama 45m radio telescope with the 25-BEam Array Receiver System. We cataloged 151 dense cores using the clumpfind method. The cores have mean radius, velocity width, and mass of 0.10+/-0.02pc, 0.53+/-0.15km/s, and 8.1+/-6.4M_{sun}_, respectively, which are very similar to those in the Orion A cloud. We examined the spatial relation between our H^13^CO^+^ cores and the 850um cores observed by Johnstone and colleagues in 2001 (Cat. J/ApJ/559/307) and 2006 (Cat. J/ApJ/639/259), and found that there are two types of spatial relationships: H^13^CO^+^ cores with and without the 850um cores. Since the mean density of the 850um cores is higher than that of the H^13^CO^+^ cores, we can interpret the H^13^CO^+^ cores with 850um cores as being more centrally concentrated and hence more evolved, compared with those without.
- ID:
- ivo://CDS.VizieR/J/A+A/288/601
- Title:
- Dense molecular cores
- Short Name:
- J/A+A/288/601
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+A/651/A59
- Title:
- Dense warm ionized medium in the inner Galaxy
- Short Name:
- J/A+A/651/A59
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Ionized interstellar gas is an important component of the interstellar medium and its lifecycle. The recent evidence for a widely distributed highly ionized warm interstellar gas with a density intermediate between the warm ionized medium (WIM) and compact HII regions suggests that there is a major gap in our understanding of the interstellar gas. Our goal is to investigate the properties of the dense warm ionized medium in the Milky Way using spectrally resolved SOFIA GREAT [NII] 205um fine-structure lines and Green Bank Telescope hydrogen radio recombination lines (RRL) data, supplemented by spectrally unresolved Herschel PACS [NII] 122um data, and spectrally resolved ^12^CO. We observed eight lines of sight (LOS) in the 20{deg}<l<30{deg}region in the Galactic plane. We spectrally unresolved Herschel PACS [NII] 122um data, and spectrally resolved ^12^CO. Methods. We observed eight lines of sight (LOS) in the 20{deg}<l<30{deg}region in the Galactic plane. We analyzed spectrally resolved lines of [NII] at 205um and RRL observations, along with the spectrally unresolved Herschel PACS 122um emission, using excitation and radiative transfer models to determine the physical parameters of the dense warm ionized medium. We derived the kinetic temperature, as well as the thermal and turbulent velocity dispersions from the [NII] and RRL linewidths. The regions with [NII] 205um emission are characterized by electron densities, n(e)~10-35cm^-3^, temperatures range from 3400 to 8500K, and nitrogen column densities N(N^+^)~7x10^16^ to 3x10^17^cm^-2^. The ionized hydrogen column densities range from 6x10^20^ to 1.7x10^21^cm^-2^ and the fractional nitrogen ion abundance x(N^+^)~1.1x10^-4^ to 3.0x10^-4^, implying an enhanced nitrogen abundance at a distance ~4.3kpc from the Galactic Center. The [NII] 205um emission lines coincide with CO emission, although often with an offset in velocity, which suggests that the dense warm ionized gas is located in, or near, star-forming regions, which themselves are associated with molecular gas. These dense ionized regions are found to contribute >~50% of the observed [CII] intensity along these LOS. The kinetic temperatures we derive are too low to explain the presence of N^+^ resulting from electron collisional ionization and/or proton charge transfer of atomic nitrogen. Rather, these regions most likely are ionized by extreme ultraviolet (EUV) radiation from nearby star-forming regions or as a result of EUV leakage through a clumpy and porous interstellar medium.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/217
- Title:
- Density distributions for mm-wave line ratios
- Short Name:
- J/ApJ/835/217
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the use of mm-wave emission line ratios to trace molecular gas density when observations integrate over a wide range of volume densities within a single telescope beam. For observations targeting external galaxies, this case is unavoidable. Using a framework similar to that of Krumholz & Thompson (2007ApJ...669..289K), we model emission for a set of common extragalactic lines from lognormal and power law density distributions. We consider the median density of gas that produces emission and the ability to predict density variations from observed line ratios. We emphasize line ratio variations because these do not require us to know the absolute abundance of our tracers. Patterns of line ratio variations have the potential to illuminate the high-end shape of the density distribution, and to capture changes in the dense gas fraction and median volume density. Our results with and without a high-density power law tail differ appreciably; we highlight better knowledge of the probability density function (PDF) shape as an important area. We also show the implications of sub-beam density distributions for isotopologue studies targeting dense gas tracers. Differential excitation often implies a significant correction to the naive case. We provide tabulated versions of many of our results, which can be used to interpret changes in mm-wave line ratios in terms of adjustments to the underlying density distributions.
- ID:
- ivo://CDS.VizieR/J/ApJ/792/43
- Title:
- Detected sources in the region of Magellanic Stream
- Short Name:
- J/ApJ/792/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the discrete clouds and filaments in the Magellanic Stream using a new high-resolution survey of neutral hydrogen (H I) conducted with the H75 array of the Australia Telescope Compact Array, complemented by single-dish data from the Parkes Galactic All-Sky Survey. From the individual and combined data sets, we have compiled a catalog of 251 clouds and listed their basic parameters, including a morphological description useful for identifying cloud interactions. We find an unexpectedly large number of head-tail clouds in the region. The implication for the formation mechanism and evolution is discussed. The filaments appear to originate entirely from the Small Magellanic Cloud and extend into the northern end of the Magellanic Bridge.
- ID:
- ivo://CDS.VizieR/J/ApJ/688/L83
- Title:
- Detection of C_5_N^-^ in IRC +10216
- Short Name:
- J/ApJ/688/L83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection in the envelope of the C-rich star IRC+10216 of four series of lines with harmonically related frequencies: B1389, B1390, B1394, and B1401. The four series must arise from linear molecules with mass and size close to those of C_6_H and C_5_N. Three of the series have half-integer rotational quantum numbers; we assign them to the ^2^{Delta} and ^2^{Sigma}^-^ vibronic states of C_6_H in its lowest ({nu}_11_) bending mode. The fourth series, B1389, has integer J with no evidence of fine or hyperfine structure; it has a rotational constant of 1388.860(2)MHz and a centrifugal distortion constant of 33(1)Hz; it is almost certainly the C_5_N^-^ anion.
- ID:
- ivo://CDS.VizieR/J/ApJS/158/188
- Title:
- Detection of glycolaldehyde toward Sgr B2
- Short Name:
- J/ApJS/158/188
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Glycolaldehyde (CHOCH_2_OH), the simplest two-carbon {alpha}-hydroxy aldehyde, has become of great interest in the field of astrochemistry due to its recent detection toward the Sagittarius B2 (N-LMH) molecular cloud. The original interstellar identification was based on an extrapolation of prior microwave rotational spectroscopy of glycolaldehyde. The millimeter and submillimeter spectra of this molecule from 128 to 354GHz were subsequently measured after the interstellar detection. We present here the millimeter spectrum of this molecule from 72 to 122.5GHz along with a combined millimeter and submillimeter pure rotational analysis of the ground and the first three vibrationally excited states of glycolaldehyde that enables a more complete molecular partition function to be determined.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A87
- Title:
- Deuteration in massive star formation process
- Short Name:
- J/A+A/575/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An ever growing number of observational and theoretical evidence suggests that the deuterated fraction (column density ratio between a species containing D and its hydrogenated counterpart, Dfrac) is an evolutionary indicator both in the low- and the high-mass star formation process. However, the role of surface chemistry in these studies has not been quantified from an observational point of view. In order to compare how the deuterated fractions of species formed only in the gas and partially or uniquely on grain surfaces evolve with time, we observed rotational transitions of CH_3_OH, ^13^CH_3_OH, CH_2_DOH, CH_3_OD at 3 and 1.3mm, and of NH_2_D at 3mm with the IRAM-30m telescope, and the inversion transitions (1,1) and (2,2) of NH_3_ with the GBT, towards most of the cores already observed by Fontani et al. (2011A&A...529L...7F, 2014MNRAS.440..448F) in N_2_H^+^, N_2_D^+^, HNC, DNC. NH_2_D is detected in all but two cores, regardless of the evolutionary stage. Dfrac(NH_3_) is on average above 0.1, and does not change significantly from the earliest to the most evolved phases, although the highest average value is found in the protostellar phase (~0.3). Few lines of CH_2_DOH and CH_3_OD are clearly detected, and only towards protostellar cores or externally heated starless cores. This work clearly confirms an expected different evolutionary trend of the species formed exclusively in the gas (N_2_D^+^ and N_2_H^+^) and those formed partially (NH_2_D and NH_3_) or totally (CH_2_DOH and CH_3_OH) on grain mantles. The study also reinforces the idea that Dfrac(N_2_H^+^) is the best tracer of massive starless cores, while high values of Dfrac(CH_3_OH) seem rather good tracers of the early protostellar phases, at which the evaporation/sputtering of the grain mantles is most efficient.
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/2907
- Title:
- 3D extinction map of northern Galactic plane
- Short Name:
- J/MNRAS/443/2907
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a three dimensional map of extinction in the Northern Galactic Plane derived using photometry from the IPHAS survey. We construct the map using a method based on a hierarchical Bayesian model as previously described by Sale (2012MNRAS.427.2119S). In addition to mean extinction, we also measure differential extinction, which arises from the fractal nature of the ISM. The method applied also furnishes us with photometric estimates of the distance, extinction, effective temperature, surface gravity, and mass for ~38 million stars. Further details about the data as well as additional formats and data products are available via http://www.iphas.org/extinction.
