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- ID:
- ivo://CDS.VizieR/J/A+A/646/A170
- Title:
- The Serpens filament 13CO, C18O and C17O datacubes
- Short Name:
- J/A+A/646/A170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Serpens filament, a prominent elongated structure in a relatively nearby molecular cloud, is believed to be at an early evolutionary stage, so studying its physical and chemical properties can shed light on filament formation and early evolution. The main goal is to address the physical and chemical properties as well as dynamical state of the Serpens filament at a spatial resolution of ~0.07pc and a spectral resolution of ~0.1~km/s. We performed ^13^CO (1-0), C^18^O (1-0), C^17^O (1-0), ^13^CO (2-1), C^18^O (2-1), and C^17^O (2-1) imaging observations toward the Serpens filament with the IRAM-3 m and APEX telescopes. Widespread narrow ^13^CO (2-1) self-absorption is observed in this filament, causing the ^13^CO morphology to be different from the filamentary structure traced by C^18^O and C^17^O. Our excitation analysis suggests that the opacities of C^18^O transitions become higher than unity in most regions, and this analysis confirms the presence of widespread CO depletion. Further we show that the local velocity gradients have a tendency to be perpendicular to the filament's long axis in the outskirts and parallel to the large-scale magnetic field direction. The magnitudes of the local velocity gradients decrease toward the filament's crest. The observed velocity structure can be a result of gravity-driven accretion flows. The isochronic evolutionary track of the C^18^O freeze-out process indicates the filament is young with an age of <~2Myr. We propose that the Serpens filament is a newly-formed slightly-supercritical structure which appears to be actively accreting material from its ambient gas.
- ID:
- ivo://CDS.VizieR/J/A+A/401/873
- Title:
- The SMC in the Far Infrared
- Short Name:
- J/A+A/401/873
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ISOPHOT experiment onboard the ISO satellite generated a complete view of the Small Magellanic Cloud (SMC) at 170{mu}m with 1.5arcmin resolution. The map is analysed using an automated photometry program enabling accurate photometric characterization of the far infrared (FIR) emitting regions. In this paper, the sources detected at 170{mu}m are compared with those obtainable from the IRAS satellite data. For this purpose, the 12{mu}m, 25{mu}m, 60{mu}m, and 100{mu}m IRAS high resolution (HiRes) maps of the SMC are re-examined using the same method. In contrast to former studies, this provides an all-band ISO/IRAS source catalog which is no longer based on eyeball classification, but relies on an algorithm which is capable of automated, repeatable photometry, even for irregular sources. In the mid infrared IRAS bands numerous bright FIR emitting regions in the SMC are detected and classified: 73 sources are found at 12{mu}m, 135 at 25{mu}m (most of them with F{nu}<1.0Jy). All three FIR bands at 170{mu}m, 100{mu}m, and 60{mu}m reproduce the overall morphological structure of the SMC similarly well, in contrast to the 12{mu}m and 25{mu}m maps which only contain a limited number of extended sources and do not trace the main body of the SMC. 243 sources are detected in the ISO 170{mu}m map, 155 of them with F{nu}>=2.0Jy. Comparable numbers are found for the two FIR IRAS maps at 60{mu}m (384) and 100{mu}m (338) with fluxes up to 450Jy. 70 of the 243 170{mu}m sources are assigned a general SED type (cold , warm , i.e., <30K, >30K) for the first time. A comparison with earlier IRAS results suggests that many source flux densities in those studies have been under- or overestimated because of non-standardized fitting methods. Many sources with flux densities up to 40Jy listed in former catalogs cannot be identified in our data.
- ID:
- ivo://CDS.VizieR/J/AJ/150/40
- Title:
- The Spitzer c2d survey of clouds. XII. Perseus
- Short Name:
- J/AJ/150/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Spitzer Space Telescope mapped the Perseus molecular cloud complex with the Infrared Array Camera (IRAC) and the Multi-Band Imaging Photometer for Spitzer (MIPS) as part of the c2d Spitzer Legacy project. This paper combines the observations from both instruments giving an overview of low-mass star formation across Perseus from 3.6 to 70{mu}m. We provide an updated list of young stellar objects (YSOs) with new classifications and source fluxes from previous works, identifying 369 YSOs in Perseus with the Spitzer data set. By synthesizing the IRAC and MIPS maps of Perseus and building on the work of previous papers in this series, we present a current census of star formation across the cloud and within smaller regions. Sixty-seven percent of the YSOs are associated with the young clusters NGC 1333 and IC 348. The majority of the star formation activity in Perseus occurs in the regions around the clusters to the eastern and western ends of the cloud complex. The middle of the cloud is nearly empty of YSOs despite containing regions of high visual extinction. The western half of Perseus contains three-quarters of the total number of embedded YSOs (Class 0+I and Flat spectral energy distribution sources) in the cloud and nearly as many embedded YSOs as Class II and III sources. Class II and III objects greatly outnumber Class 0+I objects in eastern Perseus and IC 348. These results are consistent with previous age estimates for the clusters. Across the cloud, 56% of YSOs and 91% of the Class 0+I and Flat sources are in areas where A_v_>=5mag, indicating a possible extinction threshold for star formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/741/79
- Title:
- The Spitzer-SDSS-GALEX Spectroscopic Survey
- Short Name:
- J/ApJ/741/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS) provides a new sample of 101 star-forming galaxies at z<0.2 with unprecedented multi-wavelength coverage. New mid- to far-infrared spectroscopy from the Spitzer Space Telescope is added to a rich suite of previous imaging and spectroscopy, including ROSAT, Galaxy Evolution Explorer, Sloan Digital Sky Survey, Two Micron All Sky Survey, and Spitzer/SWIRE. Sample selection ensures an even coverage of the full range of normal galaxy properties, spanning two orders of magnitude in stellar mass, color, and dust attenuation. In this paper we present the SSGSS data set, describe the science drivers, and detail the sample selection, observations, data reduction, and quality assessment.
- ID:
- ivo://CDS.VizieR/J/MNRAS/404/1321
- Title:
- TiII in Milky way and Magellanic clouds
- Short Name:
- J/MNRAS/404/1321
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss several sets of TiII absorption-line data, which probe a variety of interstellar environments in our Galaxy and in the Magellanic Clouds. Comparisons of high-resolution [full width at half-maximum (FWHM)~1.3-1.5km/s] TiII spectra of Galactic targets with corresponding high-resolution spectra of NaI, KI and CaII reveal both similarities and differences in the detailed structure of the absorption-line profiles - reflecting component-to-component differences in the ionization and depletion behaviour of those species. Moderate-resolution (FWHM~3.4-4.5km/s) spectra of more heavily reddened Galactic stars provide more extensive information on the titanium depletion in colder, denser clouds - where more than 99.9 per cent of the Ti may be in the dust phase. Moderate-resolution (FWHM~4.5-8.7km/s) spectra of stars in the Magellanic Clouds suggest that the titanium depletion is generally much less severe in the Large and Small Magellanic Clouds than in our Galaxy [for a given N(Htot), E(B-V), or molecular fraction f(H2)]- providing additional evidence for differences in depletion patterns in those two lower-metallicity galaxies. We briefly discuss possible implications of these results for the interpretation of gas-phase abundances in quasi-stellar object absorption-line systems and of variations in the D/H ratio in the local Galactic interstellar medium.
- ID:
- ivo://CDS.VizieR/J/A+A/558/A44
- Title:
- TMC-1N mapping in JHK bands
- Short Name:
- J/A+A/558/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mapping of the near-infrared (NIR) scattered light is a recent method for the study of interstellar clouds, complementing other, more commonly used methods, like dust emission and extinction. Our goal is to study the usability of this method on larger scale, and compare the properties of a filamentary structure using infrared scattering and other methods. We also study the radiation field and differences in grain emissivity between diffuse and dense areas. We have used scattered NIR J, H, and K band surface brightness observations with WFCAM instrument to map a filament TMC-1N in Taurus Molecular Cloud, covering an area of 1{deg}x1{deg} corresponding to ~(2.44pc). We have converted the data into an optical depth map and compared the results with NIR extinction and Herschel observations of sub-mm dust emission. We have also modelled the filament with 3D radiative transfer calculations of scattered light.
- ID:
- ivo://CDS.VizieR/J/A+A/653/A87
- Title:
- TOPGot sample, SEDs and CH3CN analysis
- Short Name:
- J/A+A/653/A87
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The TOPGot project targets a sample of 86 high-mass star-forming regions in different evolutionary stages from starless cores to ultra compact HII regions. The aim of the survey is to analyze different molecular species in a statistically significant sample to study the chemical evolution in high-mass star-forming regions, and identify chemical tracers of the different phases. In the first paper we present the sample and analyze the spectral energy distributions (SEDs) of the TOPGot sources to derive physical parameters. We also use the MADCUBA software to analyze the emission of methyl cyanide (CH_3_CN), a well-known tracer of high-mass star formation. The emission of the CH_3_CN(5K-4K) K-transitions has been detected towards 73 sources (85% of the sample). The emission of CH_3_CN has been detected towards all evolutionary stages, with the mean abundances showing a clear increase of an order of magnitude from high-mass starless-cores to later evolutionary stages. We found a conservative abundance upper limit for high-mass starless cores of X_CH_3_CN_<4.0x10^-11^, and a range in abundance of 4.0x10^-11^<X_CH_3_CN_<7.0x10^-11^ for those sources that are likely high-mass starless cores or very early high-mass protostellar objects. In fact, in this range of abundance we have identified five sources previously not classified as being in a very early evolutionary stage. The abundance of CH_3_CN can thus be used to identify high-mass star-forming regions in early phases of star-formation.
669. UBV photometry in W3
- ID:
- ivo://CDS.VizieR/J/AJ/129/393
- Title:
- UBV photometry in W3
- Short Name:
- J/AJ/129/393
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is generally believed that expanding superbubbles and mechanical feedback from massive stars trigger star formation, because there are numerous examples of superbubbles showing secondary star formation at their edges. However, although these systems show an age sequence, they do not provide strong evidence of a causal relationship. The W3/W4 Galactic star-forming complex suggests a three-generation hierarchy: the supergiant shell structures correspond to the oldest generation; these triggered the formation of IC 1795 in W3, the progenitor of a molecular superbubble that in turn triggered the current star-forming episodes in the embedded regions W3-North, W3-Main, and W3-OH. We present UBV photometry and spectroscopic classifications for IC 1795, which show an age of 3-5 Myr. This age is intermediate between the reported 6-20 Myr age of the supergiant shell system and the extremely young ages (10^4^-10^5^yr) for the embedded knots of the ultracompact HII regions, W3-North, W3-Main, and W3-OH. Thus, an age sequence is indeed confirmed for the entire W3/W4 hierarchical system. This therefore provides some of the first convincing evidence that superbubble action and mechanical feedback are indeed a triggering mechanism for star formation.
- ID:
- ivo://CDS.VizieR/J/ApJS/245/14
- Title:
- 8um cores in the spiral arms of nearby galaxies
- Short Name:
- J/ApJS/245/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spitzer Space Telescope observations of 15 spiral galaxies show numerous dense cores at 8{mu}m that are revealed primarily in unsharp mask images. The cores are generally invisible in optical bands because of extinction, and they are also indistinct at 8{mu}m alone because of contamination by more widespread diffuse emission. Several hundred core positions, magnitudes, and colors from the four InfraRed Array Camera bands are measured and tabulated for each galaxy. The larger galaxies, which tend to have longer and more regular spiral arms, often have their infrared cores aligned along these arms, with additional cores in spiral arm spurs. Galaxies without regular spirals have their cores in more irregular spiral-like filaments, with typically only one or two cores per filament. Nearly every elongated emission feature has 8{mu}m cores strung out along its length. The occurrence of dense cores in long and thin filaments is reminiscent of filamentary star formation in the solar neighborhood, although on a scale 100 times larger in galaxies. The cores most likely form by gravitational instabilities and cloud agglomeration in the filaments. The simultaneous occurrence of several cores with regular spacings in some spiral arms suggests that in these cases, all of the cores formed at about the same time and the corresponding filaments are young. Total star formation rates for the galaxies correlate with the total embedded stellar masses in the cores with an average ratio corresponding to a possible age between 0.2 and 2Myr. This suggests that the identified cores are the earliest phase for most star formation.
