- ID:
- ivo://CDS.VizieR/J/ApJ/891/81
- Title:
- Deep optical and infrared photometry of Sh2-305
- Short Name:
- J/ApJ/891/81
- Date:
- 17 Jan 2022 00:38:10
- Publisher:
- CDS
- Description:
- Using our deep optical and near-infrared photometry along with multiwavelength archival data, we here present a detailed study of the Galactic HII region Sh 2-305 to understand the star/star-cluster formation. On the basis of excess infrared emission, we have identified 116 young stellar objects (YSOs) within a field of view of ~18.5'x18.5' around Sh 2-305. The average age, mass, and extinction (AV) for this sample of YSOs are 1.8Myr, 2.9M_{sun}_, and 7.1mag, respectively. The density distribution of stellar sources along with minimal spanning tree calculations on the location of YSOs reveals at least three stellar subclusterings in Sh 2-305. One cluster is seen toward the center (i.e., Mayer 3), while the other two are distributed toward the north and south directions. Two massive O-type stars (VM2 and VM4; ages ~5Myr) are located at the center of the Sh 2-305 HII region. The analysis of the infrared and radio maps traces the photon-dominant regions (PDRs) in Sh 2-305. The association of the younger generation of stars with the PDRs is also investigated in Sh2-305. This result suggests that these two massive stars might have influenced the star formation history in Sh 2-305. This argument is also supported by the calculation of various pressures driven by massive stars, the slope of the mass function/K-band luminosity function, star formation efficiency, fraction of Class I sources, and mass of the dense gas toward the subclusterings in Sh 2-305.
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- ID:
- ivo://CDS.VizieR/J/A+A/574/A104
- Title:
- Dense cores in L1495/B213 complex
- Short Name:
- J/A+A/574/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cloud fragmentation into dense cores is a critical step in the process of star formation. A number of recent observations show that it is connected to the filamentary structure of the gas, but the processes responsible for core formation remain mysterious. We studied the kinematics and spatial distribution of the dense gas in the L1495/B213 filamentary region of the Taurus molecular cloud with the goal of understanding the mechanism of core formation. We mapped the densest regions of L1495/B213 in N_2_H^+^(1-0) and C_18_O(2-1) with the IRAM 30m telescope, and complemented these data with archival dust-continuum observations from the Herschel Space Observatory.
- 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.
- 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/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/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.
- ID:
- ivo://CDS.VizieR/J/A+A/591/A20
- Title:
- DIB and NaD spectra of 3 nearby stars
- Short Name:
- J/A+A/591/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Diffuse interstellar absorption bands (DIBs) of largely unknown chemical origin are regularly observed primarily in distant early-type stars. More recently, detections in nearby late-type stars have also been claimed. These stars' spectra are dominated by stellar absorption lines. Specifically, strong interstellar atomic and DIB absorption has been reported in tau Boo. We test these claims by studying the strength of interstellar absorption in high-resolution TIGRE spectra of the nearby stars tau Boo, HD 33608, and alpha CrB. We focus our analysis on a strong DIB located at 5780.61{AA} and on the absorption of interstellar Na. First, we carry out a differential analysis by comparing the spectra of the highly similar F-stars, tau Boo and HD 33608, whose light, however, samples different lines of sight. To obtain absolute values for the DIB absorption, we compare the observed spectra of tau Boo, HD 33608, and alpha CrB to PHOENIX models and carry out basic spectral modeling based on Voigt line profiles.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A108
- Title:
- DIB in VLT-FLAMES Tarantula Survey
- Short Name:
- J/A+A/550/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Tarantula Nebula (a.k.a. 30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud (LMC), seen through gas in the Galactic disc and halo. Diffuse interstellar bands (DIBs) offer a unique probe of the diffuse, cool-warm gas in these regions. The aim is to use DIBs as diagnostics of the local interstellar conditions, whilst at the same time deriving properties of the yet-unknown carriers of these enigmatic spectral features. Spectra of over 800 early-type stars from the Very Large Telescope Flames Tarantula Survey (VFTS) were analysed. Maps were created, separately, for the Galactic and LMC absorption in the DIBs at 4428 and 6614{AA} and - in a smaller region near the central cluster R 136 - neutral sodium (the NaI D doublet); we also measured the DIBs at 5780 and 5797{AA}.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/151
- Title:
- DIB Measurements in 25 atlas sightlines
- Short Name:
- J/ApJ/878/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Aiming for a new and more comprehensive DIB catalog between 4000 and 9000{AA}, we revisited the Atlas Catalog based on the observations of HD 183143 and HD 204827. Twenty-five medium to highly reddened sight lines were selected, sampling a variety of spectral types of the background star and the interstellar environments. The median signal-to-noise ratio (S/N) of these spectra is ~1300 around 6400{AA}. Compared to the Atlas Catalog, 22 new DIBs were found, and the boundaries of 27 (sets of) DIBs were adjusted, resulting in an updated catalog containing 559 DIBs that we refer to as the Apache Point Observatory Catalog of Optical Diffuse Interstellar Bands. Measurements were then made based on this catalog. We found our survey most sensitive between 5500 and 7000{AA}, due largely to the local S/N of the spectra, the relative absence of interfering stellar lines, and the weakness of telluric residuals. For our data sample, the number of DIBs detected in a given sight line is mostly dependent on E_B-V_ and less on the spectral type of the background star. Some dependence on the molecular fraction f_H2_ is observed, but it is less well determined owing to the limited size of the data sample. The variations of the wavelengths of each DIB in different sight lines are generally larger than those of the known interstellar lines CH^+^, CH, and KI. Those variations could be due to the inherent error in the measurement, or to differences in the velocity components among sight lines.
