- ID:
- ivo://CDS.VizieR/J/ApJ/699/1153
- Title:
- Kinematic distances to GRS molecular clouds
- Short Name:
- J/ApJ/699/1153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kinematic distances to 750 molecular clouds identified in the ^13^COJ=1-0 Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey (GRS) are derived assuming the Clemens rotation curve of the Galaxy. The kinematic distance ambiguity is resolved by examining the presence of HI self-absorption toward the ^13^CO emission peak of each cloud using the Very Large Array Galactic Plane Survey. We also identify 21cm continuum sources embedded in the GRS clouds in order to use absorption features in the HI 21cm continuum to distinguish between near and far kinematic distances. The Galactic distribution of GRS clouds is consistent with a four-arm model of the Milky Way. The locations of the Scutum-Crux and Perseus arms traced by GRS clouds match star-count data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire star-count data. We conclude that molecular clouds must form in spiral arms and be short-lived (lifetimes <10^7^yr) in order to explain the absence of massive, ^13^CO bright molecular clouds in the interarm space.
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- ID:
- ivo://CDS.VizieR/J/A+A/617/A27
- Title:
- Kinematics of dense gas in L1495 filament
- Short Name:
- J/A+A/617/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nitrogen bearing species, such as NH_3_, N_2_H^+^, and their deuterated isotopolo- gues show enhanced abundances in CO-depleted gas, and thus are perfect tracers of dense and cold gas in star-forming regions. The Taurus molecular cloud contains the long L1495 filament providing an excellent opportunity to study the process of star formation in filamentary environments. We study the kinematics of the dense gas of starless and protostellar cores traced by the N_2_D^+^(2-1), N_2_H^+^(1-0), DCO^+^(2-1), and H^13^CO^+^(1-0) transitions along the L1495 filament and the kinematic links between the cores and surrounding molecular cloud. We measured velocity dispersions, local and total velocity gradients, and estimate the specific angular momenta of 13 dense cores in the four transitions using on-the-fly observations with the IRAM 30-m antenna. To study a possible connection to the filament gas, we used the C^18^O(1-0) observations.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A142
- Title:
- L1544 1.2 and 2mm emission maps
- Short Name:
- J/A+A/606/A142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In dense and cold molecular clouds dust grains are surrounded by thick icy mantles. It is however not clear if dust growth and coagulation take place before the switch-on of a protostar. This is an important issue, as the presence of large grains may affect the chemical structure of dense cloud cores, including the dynamically important ionization fraction, and the future evolution of solids in protoplanetary disks. To study this further, we focus on L1544, one of the most centrally concentrated pre-stellar cores on the verge of star formation, and with a well-known physical structure. We observed L1544 at 1.2 and 2mm using NIKA, a new receiver at the IRAM 30 m telescope, and we used data from the Herschel Space Observatory archive. We find no evidence of grain growth towards the center of L1544 at the available angular resolution. Therefore, we conclude that single dish observations do not allow us to investigate grain growth towards the pre-stellar core L1544 and high sensitivity interferometer observations are needed. We predict that dust grains can grow to 200um in size toward the central ~300au of L1544. This will imply a dust opacity change by a factor of ~2.5 at 1.2mm, which can be detected using the Atacama Large Millimeter and submillimeter Array (ALMA) at different wavelengths and with an angular resolution of 2".
- ID:
- ivo://CDS.VizieR/J/A+A/652/A77
- Title:
- Large scale [CII] emission from the OMC
- Short Name:
- J/A+A/652/A77
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The [CII] 158um far-infrared (FIR) fine-structure line is one of the dominant cooling lines of the star-forming interstellar medium (ISM). Hence [CII] emission originates in, and thus can be used to trace a range of ISM processes. Velocity resolved large scale mapping of [CII] in star forming regions provides a unique perspective on the kinematics of these regions and their interactions with the exciting source of radiation. In this paper we explore the scientific applications of large scale mapping velocity resolved [CII] observations. With [CII] observations we investigate the influence of stellar feedback on the ISM. We present the details of observation, calibration and data reduction using a heterodyne array receiver mounted on an airborne observatory. A 1.15 square degree velocity resolved map of Orion molecular cloud centred on the bar region was observed using the upGREAT heterodyne receiver flying on-board the Stratospheric Observatory for Infrared Astronomy (SOFIA). The data was acquired using the 14 pixels of the German REceiver for Astronomy at Terahertz Frequencies (upGREAT) observing in an on-the-fly mapping mode. 2.4 million spectra were taken in total. These spectra were gridded into a three dimensional cube with a spatial resolution of 14.1 arcseconds and spectral resolution of 0.3km/s.
- ID:
- ivo://CDS.VizieR/J/A+A/558/A94
- Title:
- L1157 blue lobe SiO, H2CO, and CH3OH maps
- Short Name:
- J/A+A/558/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the Submillimeter Array at 1.4mm to observe the blue lobe of the L1157 outflow at high spatial resolution (~3"). We detected SiO, H_2_CO, and CH_3_OH lines from several molecular clumps that constitute the outflow. All three molecules were detected along the wall of the inner cavity that is thought to be related to the later ejection event. On the other hand, no emission was detected toward positions related to an old ejection episode, which is very likely due to space filtering from the interferometer. The H_2_CO and CH_3_OH emission is detected only at velocities close to the systemic velocity. The spatial distributions of the H_2_CO and CH_3_OH are similar. These emission lines trace the U-shaped structure seen in the mid-infrared image. In contrast, the SiO emission is detected in a wider velocity range with a peak at ~14km/s blueshifted from the systemic velocity. The SiO emission is brightest at the B1 position, which corresponds to the apex of the U-shaped structure. There are two compact SiO clumps along the faint arc-like feature to the east of the U-shaped structure. At the B1 position, there are two velocity components; one is a compact clump with a size of ~1500AU seen at high velocity, the other is an extended component with lower velocities. The kinematic structure at the B1 position is different from that expected in a single bow shock. Most likely the high-velocity SiO clump at the B1 position is kinetically independent of the low-velocity gas. The line ratio between SiO (5-4) and SiO (2-1) suggests that the high-velocity SiO clumps consist of high-density gas of n~10^5^-10^6^cm^-3^, which is similar to the density of the bullets in extremely high velocity (EHV) jets. The high-velocity SiO clumps in L1157 probably have the same origin as the EHV bullets.
- ID:
- ivo://CDS.VizieR/J/ApJ/793/126
- Title:
- L204 - Cloud 3 polarimetry and photometry
- Short Name:
- J/ApJ/793/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The L204 dark cloud complex is a nearby filamentary structure in Ophiuchus North that has no signs of active star formation. Past studies show that L204 is interacting with the nearby runaway O star, {zeta} Oph, and hosts a magnetic field that is coherent across parsec-length scales. Near-infrared H-band (1.6 {mu}m) linear polarization measurements were obtained for 3896 background stars across a 1{deg}x1.5{deg} region centered on the dense Cloud 3 in L204, using the Mimir near-infrared instrument on the 1.8 m Perkins Telescope. Analysis of these observations reveals both large-scale properties and small-scale changes in the magnetic field direction in Cloud 3. In the northern and western {zeta} Oph facing regions of the cloud, the magnetic field appears to be pushed up against the face of the cloud. This may indicate that the UV flux from {zeta} Oph has compressed the magnetic field on the western edge of L204. The plane-of-sky magnetic field strength is estimated to be ~11-26 {mu}G using the Chandrasekhar-Fermi method. The polarimetry data also reveal that the polarization efficiency (PE {equiv} P_H_/A_V_) steadily decreases with distance from {zeta} Oph (-0.09%+/-0.03%/mag/pc). Additionally, power-law fits of PE versus A_V_ for localized samples of probe stars show steeper negative indices with distance from {zeta} Oph. Both findings highlight the importance of external illumination, here from {zeta} Oph, in aligning dust grains to embedded magnetic fields.
- ID:
- ivo://CDS.VizieR/J/A+A/611/A9
- Title:
- LDN 183 and LDN 169 Vilnius photometry
- Short Name:
- J/A+A/611/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interstellar extinction is investigated in a 2x2deg area containing the dust and molecular clouds LDN 183 (MBM 37) and LDN 169, centered at RA=15h54m, DEC=-3{deg}. The study is based on photometric classification in spectral and luminosity classes of 782 stars selected from the catalogs of 1299 stars down to V=20mag observed in the Vilnius seven-color system. For control, the MK types for 18 brightest stars with V between 8.5 and 12.8mag were determined spectroscopically. For 14 stars, located closer than 200pc, distances were calculated from trigonometric parallaxes taken from the Gaia Data Release 1. For about 70% of the observed stars, two-dimensional spectral types, interstellar extinctions Av and distances were determined. Using 57 stars closer than 200pc we estimate that the front edge of the clouds begins at 105+/-8pc. The extinction layer in the vicinities of the clouds can be about 20pc thick. In the outer parts of the clouds and between the clouds the extinction is 2.0-2.5mag. Behind the Serpens/Libra clouds the extinction range does not increase; this means that the dust layer at 105pc is a single extinction source.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A65
- Title:
- LDN 1570 BV(RI)c polarisation and photometry
- Short Name:
- J/A+A/556/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We wish to map the magnetic field geometry and to study the dust properties of the starless cloud, L1570, using multiwavelength optical polarimetry and photometry of the stars projected on the cloud. We made R-band imaging polarimetry of the stars projected on a cloud, L1570, to trace the magnetic field orientation. We also made multi-wavelength polarimetric and photometric observations to constrain the properties of dust in L1570. We estimated a distance of 394+/-70pc to the cloud using 2MASS JHKs colours. Using the values of the Serkowskiparameters namely {sigma}_1_, {overline}{epsilon}, {lambda}_max_ and the position of the stars on near infrared color-color diagram, we identified 13 stars that could possibly have intrinsic polarization and/or rotation in their polarization angles. One star, 2MASS J06075075+1934177, which is a B4Ve spectral type, show the presence of diffuse interstellar bands in the spectrum apart from showing H_{alpha} line in emission. There is an indication for the presence of slightly bigger dust grains towards L1570 on the basis of the dust grain size-indicators such as {lambda}_max_ and R_V_ values. The magnetic field lines are found to be parallel to the cloud structures seen in the 250um images (also in 8um and 12um shadow images) of L1570. Based on the magnetic field geometry, the cloud structure and the complex velocity structure, we believe that L1570 is in the process of formation due to the converging flow material mediated by the magnetic field lines. Structure function analysis showed that in the L1570 cloud region the large scale magnetic fields are stronger when compared with the turbulent component of magnetic fields. The estimated magnetic field strengths suggest that the L1570 cloud region is sub-critical and hence could be strongly supported by the magnetic field lines.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/1008
- Title:
- LDN 1495 SCUBA-2 and Herschel data
- Short Name:
- J/MNRAS/463/1008
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comparison of Submillimetre Common User Bolometer Array-2 (SCUBA-2) 850-{mu}m and Herschel 70-500-{mu}m observations of the L1495 filament in the Taurus Molecular Cloud with the goal of characterizing the SCUBA-2 Gould Belt Survey (GBS) data set. We identify and characterize starless cores in three data sets: SCUBA-2 850-{mu}m, Herschel 250-{mu}m, and Herschel 250-{mu}m spatially filtered to mimic the SCUBA-2 data. SCUBA-2 detects only the highest-surface-brightness sources, principally detecting protostellar sources and starless cores embedded in filaments, while Herschel is sensitive to most of the cloud structure, including extended low-surface-brightness emission. Herschel detects considerably more sources than SCUBA-2 even after spatial filtering. We investigate which properties of a starless core detected by Herschel determine its detectability by SCUBA-2, and find that they are the core's temperature and column density (for given dust properties). For similar-temperature cores, such as those seen in L1495, the surface brightnesses of the cores are determined by their column densities, with the highest-column-density cores being detected by SCUBA-2. For roughly spherical geometries, column density corresponds to volume density, and so SCUBA-2 selects the densest cores from a population at a given temperature. This selection effect, which we quantify as a function of distance, makes SCUBA-2 ideal for identifying those cores in Herschel catalogues that are closest to forming stars. Our results can now be used by anyone wishing to use the SCUBA-2 GBS data set.
- ID:
- ivo://CDS.VizieR/J/A+A/547/A12
- Title:
- Leading arm Magellanic Cloud Catalog
- Short Name:
- J/A+A/547/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Magellanic Cloud system (MCS) interacts via tidal and drag forces with the Milky Way galaxy. Using the Parkes Galactic All-Sky Survey (GASS) of atomic hydrogen we explore the role of drag on the evolution of the so-called Leading Arm (LA).
