- ID:
- ivo://CDS.VizieR/J/A+A/604/A20
- Title:
- L1157-B1 DCN (2-1) and H^13^CN (2-1) datacubes
- Short Name:
- J/A+A/604/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed high-angular-resolution observations toward L1157-B1 with the IRAM NOEMA interferometer of the DCN (2-1) and H^13^CN (2-1) lines to compute the deuterated fraction, D_frac_(HCN), and compare it with previously reported D_frac_ of other molecular species. Our aim is to observationally investigate the role of the different chemical processes at work that lead to formation of the DCN and compare it with HDCO, the two deuterated molecules imaged with an interferometer, and test the predictions of the chemical models for their formation.
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Search Results
- 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/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/497/1972
- Title:
- LEGO II. 3mm molecular line study
- Short Name:
- J/MNRAS/497/1972
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The current generation of (sub)mm-telescopes have allowed molecular line emission to become a major tool for studying the physical, kinematic, and chemical properties of extra-galactic systems, yet exploiting these observations requires a detailed understanding of where emission lines originate within the Milky Way. In this paper, we present 60" (~3pc) resolution observations of many 3mm-band molecular lines across a large map of the W49 massive star-forming region (~100pcx100pc at 11kpc), which were taken as part of the "LEGO" IRAM-30m large project. We find that the spatial extent or brightness of the molecular line transitions are not well correlated with their critical densities, highlighting abundance and optical depth must be considered when estimating line emission characteristics. We explore how the total emission and emission efficiency (i.e. line brightness per H_2_ column density) of the line emission vary as a function of molecular hydrogen column density and dust temperature. We find that there is not a single region of this parameter space responsible for the brightest and most efficiently emitting gas for all species. For example, we find that the HCN transition shows high emission efficiency at high column density (10^22^cm^-2^) and moderate temperatures (35K), whilst e.g. N_2_H^+^ emits most efficiently towards lower temperatures (10^22^cm^-2^; <20K). We determine X_CO(1-0)_~0.3x10^20^cm^-2^/(K.km/s), and {alpha}_HCN(1-0)_~30M_{sun}_/(K.(km/s)pc^2^), which both differ significantly from the commonly adopted values. In all, these results suggest caution in interpreting molecular line emission.
- ID:
- ivo://CDS.VizieR/VIII/76
- Title:
- Leiden/Argentine/Bonn (LAB) Survey of Galactic HI
- Short Name:
- VIII/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The LAB survey contains the final data release of observations of 21-cm emission from Galactic neutral hydrogen over the entire sky, merging the Leiden/Dwingeloo Survey (LDS: Hartmann & Burton 1997, Cat. VIII/54) of the sky north of -30{deg} with the Instituto Argentino de Radioastronomia Survey (IAR: Arnal et al. 2000A&AS..142...35A and Bajaja et al. 2005, Cat. VIII/75) of the sky south of -25{deg}. The angular resolution of the combined material is HPBW ~ 0.6{deg}. The LSR velocity coverage spans the interval -450 km/s to +400 km/s, at a resolution of 1.3km/s. The data were corrected for stray radiation at the Institute for Radioastronomy of the University of Bonn, refining the original correction applied to the LDS. The rms brightness-temperature noise of the merged database is 0.07-0.09 K. Residual errors in the profile wings due to defects in the correction for stray radiation are for most of the data below a level of 20-40 mK. It would be necessary to construct a telescope with a main beam efficiency of {eta}MB>99% to achieve the same accuracy. The merged and refined material entering the LAB Survey of Galactic H I is intended to be a general resource useful to a wide range of studies of the physical and structural characteristices of the Galactic interstellar environment. The LAB Survey is the most sensitive Milky Way H I survey to date, with the most extensive coverage both spatially and kinematically. The Survey is available as 3-D maps, with or without Hanning smoothing, covering the whole +/-458km/s or limited to +/-250km/s range. The resolution of the 3-D maps is 0.5{deg} in galactic longitude and latitude, and up to 1km/s in velocity. The survey exists also as (b,v) maps at longitude intervals stepped by 0.5{deg} -- these files supersedes the FITS files given in the Hartmann and Burton Atlas (Cat. VIII/54)
- ID:
- ivo://CDS.VizieR/J/A+A/632/A115
- Title:
- L1188 HCO+, 12CO and 13CO datacubes
- Short Name:
- J/A+A/632/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to search for further observational evidence of cloud-cloud collisions in one of the promising candidates, L1188, we carried out observations of multiple molecular lines toward the intersection region of the two nearly orthogonal filamentary molecular clouds in L1188. Based on these observations, we find two parallel filamentary structures, both of which have at least two velocity components being connected with broad bridging features. We also found a spatially complementary distribution between the two molecular clouds, as well as enhanced ^13^CO emission and ^12^CO self-absorption toward their abutting regions. At the most blueshifted velocities, we unveiled a 1pc-long arc ubiquitously showing ^12^CO line wings. We discovered two 22GHz water masers, which are the first maser detections in L1188. An analysis of line ratios at a linear resolution of 0.2 pc suggests that L1188 is characterised by kinetic temperatures of 13-23K and H_2_ number densities of 10^3^-10^3.6^cm^-3^. On the basis of previous theoretical predictions and simulations, we suggest that these observational features can be naturally explained by the scenario of a cloud-cloud collision in L1188, although an additional contribution of stellar feedback from low-mass young stellar objects cannot be ruled out.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A25
- Title:
- Linear and circular polarisation spectra of 2 stars
- Short Name:
- J/A+A/531/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The identification of the carriers of diffuse interstellar bands (DIBs) remains one of the long-standing mysteries in astronomy. The detection of a polarisation signal in a DIB profile can be used to distinguish between a dust or gas-phase carrier. The polarisation profile can give additional information on the grain or molecular properties of the absorber. The aim is to measure the polarisation efficiency of the carriers of the diffuse interstellar bands.
- ID:
- ivo://CDS.VizieR/J/ApJS/141/469
- Title:
- Linear polarization catalog toward HD 62542
- Short Name:
- J/ApJS/141/469
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained linear polarization measurements of stars along the western side of the IRAS Vela Shell toward HD 62542. From 16 CCD fields distributed along the ionization front (I-front) we have built a catalog of 856 objects with polarization signal-to-noise ratio larger than 10. We detect very significant levels of polarization and hence an appreciable magnetic field throughout the region. Composite polarization maps around the I-front are shown. In some regions the polarization vectors are parallel to the I-front, but a perpendicular trend is also evident along parts of the front. In addition, the polarization pattern seems to be affected by gas streaming inside the cloud. The observations were made using a CCD imaging polarimeter attached to the 1.5m Telescope of Cerro Tololo Inter-American Observatory (CTIO), Chile. The data were collected in 1991 December and 1992 December.
- ID:
- ivo://CDS.VizieR/J/ApJ/783/36
- Title:
- Linelists for C3H- from CALPGM
- Short Name:
- J/ApJ/783/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Pety et al. have reported the detection of eight transitions of a closed-shell, linear molecule (B11244) in observations toward the Horsehead photodissociation region (PDR), which they attribute to the l-C_3_H^+^ cation. Recent high-level ab initio calculations have called this assignment into question; the anionic C_3_H^-^ molecule has been suggested as a more likely candidate. Here, we examine observations of the Horsehead PDR, Sgr B2(N), TMC-1, and IRC+10216 in the context of both l-C_3_H^+^ and C_3_H^-^. We find no observational evidence of K_a_=1 lines, which should be present were the carrier indeed C_3_H^-^. Additionally, we find a strong anticorrelation between the presence of known molecular anions and B11244 in these regions. Finally, we discuss the formation and destruction chemistry of C_3_H^-^ in the context of the physical conditions in the regions. Based on these results, we conclude there is little evidence to support the claim that the carrier is C_3_H^-^.
- ID:
- ivo://CDS.VizieR/J/ApJ/783/77
- Title:
- Line lists of transitions for interstellar urea
- Short Name:
- J/ApJ/783/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the results of an observational search for gas phase urea [(NH_2_)_2_CO] observed toward the Sgr B2(N-LMH) region. We show data covering urea transitions from ~100GHz to 250GHz from five different observational facilities: the Berkeley-Illinois-Maryland-Association (BIMA) Array, the Combined Array for Research in Millimeter-wave Astronomy (CARMA), the NRAO 12m telescope, the IRAM 30m telescope, and the Swedish-ESO Submillimeter Telescope (SEST). The results show that the features ascribed to urea can be reproduced across the entire observed bandwidth and all facilities by best-fit column density, temperature, and source size parameters which vary by less than a factor of two between observations merely by adjusting for telescope-specific parameters. Interferometric observations show that the emission arising from these transitions is cospatial and compact, consistent with the derived source sizes and emission from a single species. Despite this evidence, the spectral complexity of both (NH_2_)_2_ CO and of Sgr B2(N) makes the definitive identification of this molecule challenging. We present observational spectra, laboratory data, and models, and discuss our results in the context of a possible molecular detection of urea.
