- ID:
- ivo://CDS.VizieR/J/A+A/608/A146
- Title:
- Southern Hemisphere ISM FORS2 spectropolarimetry
- Short Name:
- J/A+A/608/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Polarimetric studies of light transmitted through interstellar clouds may give constraints on the properties of the interstellar dust grains. Traditionally, broadband linear polarisation (BBLP) measurements have been considered an important diagnostic tool for the study of the interstellar dust, while comparatively less attention has been paid to spectropolarimetric measurements. However, spectropolarimetry may offer stronger constraints than BBLP, for example by revealing narrowband features, and by allowing us to distinguish the contribution of dust from the contribution of interstellar gas. Therefore, we have decided to carry out a Large Interstellar Polarisation Survey (LIPS) using spectropolarimetric facilities in both hemispheres. Here we present the results obtained in the Southern Hemisphere with the FORS2 instrument of the ESO Very Large Telescope.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/897/176
- Title:
- 19 species in 14 super stars clusters in NGC 253
- Short Name:
- J/ApJ/897/176
- Date:
- 14 Mar 2022 07:03:40
- Publisher:
- CDS
- Description:
- We present submillimeter spectra of the (proto-)super star cluster (SSC) candidates in the starbursting center of the nearby galaxy NGC 253 identified by Leroy et al. The 2.5pc resolution of our Atacama Large Millimeter/submillimeter Array cycle 3 observations approaches the size of the SSCs and allows for the study of physical and chemical properties of the molecular gas in these sources. In the 14 SSC sources and in the frequency ranges 342.0-345.8GHz and 353.9-357.7GHz, we detect 55 lines belonging to 19 different chemical species. The SSCs differ significantly in chemical complexity, with the richest clusters showing 19 species and the least complex showing four species. We detect HCN isotopologues and isomers (H13CN, HC15N, H15NC), abundant HC3N, SO and S18O, SO2, and H2CS. The gas ratios CO/HCN, CO/HCO+ are low, ~1-10, implying high dense gas fractions in the SSCs. Line ratio analyses suggests chemistry consistent with photon-dominated regions and mechanical heating. None of the SSCs near the galaxy center show line ratios that imply an X-ray-dominated region, suggesting that heating by any (still unknown) active galactic nucleus does not play a major role. The gas temperatures are high in most sources, with an average rotational temperature of ~130K in SO2. The widespread existence of vibrationally excited HCN and HC3N transitions implies strong infrared radiation fields, potentially trapped by a greenhouse effect due to high continuum opacities.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A37
- Title:
- Spectral cube toward NGC 6334 I and I(N)
- Short Name:
- J/A+A/593/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HF molecule has been proposed as a sensitive tracer of diffuse interstellar gas, while at higher densities its abundance could be influenced heavily by freeze-out onto dust grains. We investigate the spatial distribution of a collection of absorbing gas clouds, some associated with the dense, massive star-forming core NGC 6334 I, and others with diffuse foreground clouds elsewhere along the line of sight. For the former category, we aim to study the dynamical properties of the clouds in order to assess their potential to feed the accreting protostellar cores. We use far-infrared spectral imaging from the Herschel SPIRE iFTS to construct a map of HF absorption at 243um in a 6'x3.5' region surrounding NGC 6334 I and I(N).
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/3842
- Title:
- Spectral line survey of two LOSs
- Short Name:
- J/MNRAS/446/3842
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of two Mopra 3-mm spectral line surveys of the lines of sight (LOS) towards the Galactic Centre (GC) molecular complexes Sgr B2 (LOS+0.693) and Sgr A (LOS-0.11). The spectra covered the frequency ranges of ~77-93 GHz and ~105-113 GHz. We have detected 38 molecular species and 25 isotopologues. The isotopic ratios derived from column density ratios are consistent with the canonical values, indicating that chemical isotopic fractionation and/or selective photodissociation can be considered negligible (<10 percent) for the GC physical conditions. The derived abundances and rotational temperatures are very similar for both LOSs, indicating very similar chemical and excitation conditions for the molecular gas in the GC. The excitation conditions are also very similar to those found for the nucleus of the starburst galaxy NGC 253. We report for the first time the detection of HCO and HOC^+^ emission in LOS+0.693. Our comparison of the abundance ratios between CS, HCO, HOC^+^ and HCO^+^ found in the two LOSs with those in typical Galactic photodissociation regions (PDRs) and starbursts galaxies does not show any clear trend to distinguish between ultraviolet- and X-ray-induced chemistries. We propose that the CS/HOC^+^ ratio could be used as a tracer of the PDR components in the molecular clouds in the nuclei of galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/232/3
- Title:
- Spectral line surveys of 30 regions
- Short Name:
- J/ApJS/232/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectral line surveys are an indispensable tool for exploring the physical and chemical evolution of astrophysical environments due to the vast amount of data that can be obtained in a relatively short amount of time. We present deep, broadband spectral line surveys of 30 interstellar clouds using two broadband {lambda}=1.3mm receivers at the Caltech Submillimeter Observatory. This information can be used to probe the influence of physical environment on molecular complexity. We observed a wide variety of sources to examine the relative abundances of organic molecules as they relate to the physical properties of the source (i.e., temperature, density, dynamics, etc.). The spectra are highly sensitive, with noise levels <=25mK at a velocity resolution of ~0.35km/s. In the initial analysis presented here, column densities and rotational temperatures have been determined for the molecular species that contribute significantly to the spectral line density in this wavelength regime. We present these results and discuss their implications for complex molecule formation in the interstellar medium.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A127
- Title:
- Spectroscopy of CD_3_OH
- Short Name:
- J/A+A/658/A127
- Date:
- 20 Mar 2022 08:37:11
- Publisher:
- CDS
- Description:
- Solar-type protostars have been shown to harbor highly deuterated complex organics as for example witnessed by the high relative abundances of doubly and triply deuterated isotopologs. While this degree of deuteration may provide important clues to the formation of these species, spectroscopic information on multiply deuterated isotopologs is often insufficient. In particular, searches for triply deuterated methanol, CD_3_OH, are hampered to a large extent by the lack of intensity information from a spectroscopic model. The aim of the present study is to develop a spectroscopic model of CD_3_OH in low-lying torsional states sufficiently accurate to facilitate further searches for CD_3_OH in space. We have performed a new measurement campaign for CD_3_OH involving three spectroscopic laboratories which covers the 34GHz-1.1THz and the 20-900cm^-1^ ranges. The analysis was perfomed using the rho-axis-method torsion- rotation Hamiltonian model. We determined a model that describes the ground and first excited torsional states of CD_3_OH up to quantum numbers J<=55 and K<=23, and derived a line list for radio-astronomical observations. The resulting line list is accurate up to at least 1.1THz and should be sufficient for all types of radio-astronomical searches for this methanol isotopolog. This line list was used to search for CD_3_OH in data from the Protostellar Interferometric Line Survey of IRAS 16293-2422 using the Atacama Large Millimeter/submillimeter Array. CD_3_OH is securely detected in the data with a large number of clearly separated and well-reproduced lines. We detected not only lines belonging to the ground torsional state, but also several belonging to the first excited torsional state. The derived column density of CD_3_OH and abundance relative to non-deuterated isotopolog confirm the significant enhancement of this multiply deuterated variant. This is in line with other observations of multiply deuterated complex organic molecules and may serve as an important constraint on models for their formation.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A162
- Title:
- Spectroscopy of CH2(CN)2 and CNCH2CN
- Short Name:
- J/A+A/623/A162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nitriles constitute almost 20% of the molecules observed in the interstellar medium, whereas only one dinitrile and one isocyanonitrile compound have been detected up to now. The lack of detections of such compounds may be partially explained by the lack of accurate spectroscopic data on their rotational spectra. Two small seven-atom dinitriles, malononitrile NCCH_2_CN and isocyanoacetonitrile NCCH_2_NC, were chosen as target species for this study. For malononitrile the goal of the study is to systematize all the previous measurements, and to extend the measurements to the sub-millimeter wavelength range. The spectrum of isocyanoacetonitrile has not been studied before. The rotational spectra of the two molecules was measured in the frequency range 150-660GHz using the Lille fast-scan spectrometer. The spectroscopic study was supported by high-level theoretical calculations on the structure of these molecules and their harmonic force field. Accurate frequency predictions for malononitrile and isocyanoacetonitrile were calculated on the basis of the analysis of their rotational spectra. The influence of the spin statistics on the intensities of the lines of malononitrile was taken into account. The provided line lists and sets of molecular parameters meet the needs of astrophysical searches for the two molecules.
- ID:
- ivo://CDS.VizieR/J/AJ/149/79
- Title:
- Spectroscopy of 299 galaxies from NewHa survey
- Short Name:
- J/AJ/149/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a sample of 299 H{alpha}-selected galaxies at z~~0.8, we study the relationship between galaxy stellar mass, gas-phase metallicity, and star formation rate (SFR), and compare to previous results. We use deep optical spectra obtained with the IMACS spectrograph at the Magellan telescope to measure strong oxygen lines. We combine these spectra and metallicities with (1) rest-frame UV-to-optical imaging, which allows us to determine stellar masses and dust attenuation corrections, and (2) H{alpha} narrowband imaging, which provides a robust measurement of the instantaneous SFR. Our sample spans stellar masses of ~10^9^-6x10^11^M_{sun}_, SFRs of 0.4-270M_{sun}_/yr, and metal abundances of 12+log(O/H)~~8.3-9.1(~~0.4-2.6Z_{sun}_). The correlations that we find between the H{alpha}-based SFR and stellar mass (i.e., the star-forming "main sequence") and between the stellar mass and metallicity are both consistent with previous z~1 studies of star-forming galaxies. We then study the relationship between the three properties using various plane-fitting techniques and a curve-fitting projection. In all cases, we exclude strong dependence of the M_{star}_-Z relation on SFR, but are unable to distinguish between moderate and no dependence. Our results are consistent with previous mass-metallicity-SFR studies. We check whether data set limitations may obscure a strong dependence on the SFR by using mock samples drawn from the Sloan Digital Sky Survey. These experiments reveal that the adopted signal-to-noise ratio cuts may have a significant effect on the measured dependence. Further work is needed to investigate these results, and to test whether a "fundamental metallicity relation" or a "fundamental plane" describes star-forming galaxies across cosmic time.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A53
- Title:
- Spectroscopy of Herschel Dwarf Galaxy Survey
- Short Name:
- J/A+A/578/A53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Herschel PACS spectroscopic observations of the [CII] 157um, [OI] 63 and 145um, [OIII] 88um, [NII] 122 and 205um, and [NIII] 57um fine-structure cooling lines in a sample of 48 low-metallicity star-forming galaxies of the guaranteed time key program Dwarf Galaxy Survey. We correlate PACS line ratios and line-to-LTIR ratios with LTIR, LTIR/LB, metallicity, and FIR color, and interpret the observed trends in terms of ISM conditions and phase filling factors with Cloudy radiative transfer models. We find that the ISM of low-metallicity dwarf galaxies has a more porous structure than that of metal-rich galaxies. The radiation fields are harder and the the ionized gas/PDR filling factor is larger in the dwarfs.
- ID:
- ivo://CDS.VizieR/J/AJ/130/1707
- Title:
- Spectroscopy of the LV2 proplyd in Orion
- Short Name:
- J/AJ/130/1707
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high spatial resolution spectroscopic observations of the proplyd 167-317 (LV2) near the Trapezium cluster in the Orion Nebula, obtained during the system verification run of the Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU) at the Gemini South Observatory. We have detected 38 forbidden and permitted emission lines associated with the proplyd and its redshifted jet.