Search

Start Over Subject spectroscopy Content Level Research
801. Formamide detection with ASAI-IRAM
ID:
ivo://CDS.VizieR/J/MNRAS/449/2438
Title:
Formamide detection with ASAI-IRAM
Short Name:
J/MNRAS/449/2438
Date:
21 Oct 2021
Publisher:
CDS
Description:
Formamide (NH_2_CHO) has been proposed as a pre-biotic precursor with a key role in the emergence of life on Earth. While this molecule has been observed in space, most of its detections correspond to high-mass star-forming regions. Motivated by this lack of investigation in the low-mass regime, we searched for formamide, as well as isocyanic acid (HNCO), in 10 low- and intermediate-mass pre-stellar and protostellar objects. The present work is part of the IRAM Large Programme ASAI (Astrochemical Surveys At IRAM), which makes use of unbiased broad-band spectral surveys at millimetre wavelengths. We detected HNCO in all the sources and NH_2_CHO in five of them. We derived their abundances and analysed them together with those reported in the literature for high-mass sources. For those sources with formamide detection, we found a tight and almost linear correlation between HNCO and NH_2_CHO abundances, with their ratio being roughly constant - between 3 and 10 - across 6 orders of magnitude in luminosity. This suggests the two species are chemically related. The sources without formamide detection, which are also the coldest and devoid of hot corinos, fall well off the correlation, displaying a much larger amount of HNCO relative to NH_2_CHO. Our results suggest that, while HNCO can be formed in the gas-phase during the cold stages of star formation, NH_2_CHO forms most efficiently on the mantles of dust grains at these temperatures, where it remains frozen until the temperature rises enough to sublimate the icy grain mantles. We propose hydrogenation of HNCO as a likely formation route leading to NH_2_CHO.
802. Formation of MW halo and its dwarf satellites
ID:
ivo://CDS.VizieR/J/A+A/604/A129
Title:
Formation of MW halo and its dwarf satellites
Short Name:
J/A+A/604/A129
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a homogeneous set of accurate atmospheric parameters for a complete sample of very and extremely metal-poor stars in the dwarf spheroidal galaxies (dSphs) Sculptor, Ursa Minor, Sextans, Fornax, Bootes I, Ursa Major II, and Leo IV. We also deliver a Milky Way (MW) comparison sample of giant stars covering the -4<[Fe/H]<-1.7 metallicity range. We show that, in the [Fe/H]=>-3.7 regime, the non-local thermodynamic equilibrium (NLTE) calculations with non-spectroscopic effective temperature (Teff) and surface gravity (log g) based on the photometric methods and known distance provide consistent abundances of the FeI and FeII lines. This justifies the FeI/FeII ionisation equilibrium method to determine log g for the MW halo giants with unknown distance. The atmospheric parameters of the dSphs and MW stars were checked with independent methods. In the [Fe/H]>-3.5 regime, the TiI/TiII ionisation equilibrium is fulfilled in the NLTE calculations. In the logg-Teff plane, all the stars sit on the giant branch of the evolutionary tracks corresponding to [Fe/H]=-2 to -4, in line with their metallicities. For some of the most metal-poor stars of our sample, we hardly achieve consistent NLTE abundances from the two ionisation stages for both iron and titanium. We suggest that this is a consequence of the uncertainty in the Teff-colour relation at those metallicities. The results of these work provide the base for a detailed abundance analysis presented in a companion paper.
803. FORS1 catalogue of stellar magnetic fields
ID:
ivo://CDS.VizieR/J/A+A/583/A115
Title:
FORS1 catalogue of stellar magnetic fields
Short Name:
J/A+A/583/A115
Date:
21 Oct 2021
Publisher:
CDS
Description:
The FORS1 instrument of the ESO Very Large Telescope was used to obtain low resolution circular polarized spectra of nearly a thousand of different stars, with the aim of measuring their mean longitudinal magnetic fields. Magnetic fields were measured by different authors, and using different methods and software tools. A catalogue of FORS1 magnetic measurements would provide a valuable resource with which to better understand the strengths and limitations of this instrument and of similar low-dispersion, Cassegrain spectropolarimeters. However, FORS1 data reduction has been carried out by a number of different groups using a variety of reduction and analysis techniques. Both our understanding of the instrument and our data reduction techniques have improved over time. A full re-analysis of FORS1 archive data using a consistent and fully documented algorithm would optimise the accuracy and usefulness of a catalogue of field measurements. Based on ESO FORS pipeline, we have developed a semi-automatic procedure for magnetic field determinations, which includes self-consistent checks for field detection reliability. We have applied our procedure to the full content of circular spectropolarimetric measurements of the FORS1 archive. We have produced a catalogue of spectro-polarimetric observations and magnetic field measurements for 1400 observations of 850 different objects. The spectral type of each object has been accurately classified. We have also been able to test different methods for data reduction is a systematic way. The resulting catalogue has been used to produce an estimator for an upper limit to the uncertainty in a field strength measurement of an early type star as a function of the signal-to-noise ratio of the observation. While FORS1 is not necessarily an optimal instrument for the discovery of weak magnetic fields, it is very useful for the systematic study of larger fields, such as those found in Ap/Bp stars and in white dwarfs.
804. FORS spectroscopy of HDFS galaxies
ID:
ivo://CDS.VizieR/J/A+A/440/61
Title:
FORS spectroscopy of HDFS galaxies
Short Name:
J/A+A/440/61
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present low resolution multi-object spectroscopy of an I-band magnitude limited (I_AB_~23-23.5) sample of galaxies located in an area centered on the Hubble Deep Field-South (HDFS). The observations were obtained using the Focal Reducer/low dispersion Spectrograph (FORS) on the ESO Very Large Telescope. Thirty-two primary spectroscopic targets in the HST-WFPC2 HDFS were supplemented with galaxies detected in the Infrared Space Observatory's survey of the HDFS and the ESO Imaging Deep Survey to comprise a sample of 100 galaxies for spectroscopic observations. Based on detections of several emission lines, such as [OII]3727, H{beta} and [OIII]5007, or of other spectroscopic features, we measured accurate redshifts for 50 objects in the central HDFS and flanking fields. The redshift range of the current sample of galaxies is 0.6-1.2, with a median redshift of 1.13 (at I~23.5 not corrected for completeness). The sample is dominated by starburst galaxies with only a small fraction of ellipticals (~10%). For the emission line objects, the extinction corrected [OII]3727 line strengths yield estimates of star formation rates in the range 0.5-30M_{sun}_/yr. We used the present data to derive the [OII]3727 luminosity function up to redshift of 1.2. When combined with [OII]3727 luminosity densities for the local and high redshift Universe, our results confirm the steep rise in the star formation rate (SFR) to z~1.3.
805. FORS2 transmission spectroscopy of WASP-17b
ID:
ivo://CDS.VizieR/J/A+A/596/A47
Title:
FORS2 transmission spectroscopy of WASP-17b
Short Name:
J/A+A/596/A47
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present FORS2 (attached to ESO's Very Large Telescope) observations of the exoplanet WASP-17b during its primary transit, for the purpose of differential spectrophotometry analysis. We use the instrument in its Mask eXchange Unit (MXU) mode to simultaneously obtain low resolution spectra of the planet hosting star, as well as several reference stars in the field of view. The integration of these spectra within broadband and smaller 100{AA} bins provides us with 'white' and spectrophotometric light curves, from 5700 to 8000{AA}. Through modelling the white light curve, we obtain refined bulk and transit parameters of the planet, as well as wavelength-dependent variations of the planetary radius from smaller spectral bins through which the transmission spectrum is obtained. The inference of transit parameters, as well as the noise statistics, is performed using a Gaussian Process model. We achieve a typical precision in the transit depth of a few hundred parts per million from various transit light curves. From the transmission spectra we rule out a flat spectrum at >3{sigma} and detect marginal presence of the pressure-broadened sodium wings. Furthermore, we detect the wing of the potassium absorption line in the upper atmosphere of the planet with 3-{sigma} confidence, both facts pointing to a relatively shallow temperature gradient in the atmosphere. These conclusions are mostly consistent with previous studies of this exo-atmosphere, although previous potassium measurements have been inconclusive.
806. Fourier transform emission spectroscopy of ^13^C^14^N
ID:
ivo://CDS.VizieR/J/ApJS/194/34
Title:
Fourier transform emission spectroscopy of ^13^C^14^N
Short Name:
J/ApJS/194/34
Date:
21 Oct 2021
Publisher:
CDS
Description:
Emission spectra of the B^2^{Sigma}^+^-X^2^{Sigma}^+^ transition of ^13^C^14^N have been observed at high resolution using the Fourier transform spectrometer associated with the McMath-Pierce Solar Telescope of the National Solar Observatory. The spectra have been measured in the 21000-30000cm^-1^ region and a total of 52 vibrational bands involving vibrational levels up to {nu}=15 of the ground and excited states have been rotationally analyzed to provide a much improved set of spectroscopic constants. An experimental line list and calculated term values are provided. The results of the present analysis should prove useful in the identification of additional ^13^C^14^N lines in comets and cool stars, and will help in the determination of the ^12^C/^13^C abundance ratio.
807. Frequency analysis of HD 49434
ID:
ivo://CDS.VizieR/J/A+A/525/A23
Title:
Frequency analysis of HD 49434
Short Name:
J/A+A/525/A23
Date:
21 Oct 2021
Publisher:
CDS
Description:
HD 49434 is a bright (V=5.75mag) and multiperiodic gamma Dor-type pulsator that has been selected for the asteroseismic core programme of the CoRoT satellite. An extensive and detailed study has been carried out to investigate the pulsational content of this object on the basis of the 136.9d (331291 useful datapoints) time series collected by the CoRoT satellite during the long-run LRa01 (October 2007-March 2008).
808. Fried Egg Nebula AMBER and GRAVITY observations
ID:
ivo://CDS.VizieR/J/A+A/635/A183
Title:
Fried Egg Nebula AMBER and GRAVITY observations
Short Name:
J/A+A/635/A183
Date:
21 Oct 2021
Publisher:
CDS
Description:
The objective of this work is to study in detail the nature (i.e., geometry, rates) of the mass-loss episodes associated with the yellow hypergiant IRAS 17163-3907. We analysed a large set of optical/near-infrared data, in spectroscopic, photometric, spectropolarimetric, and interferometric modes. We use the optical observations to determine its spectral type and we present the first model independent reconstructed images of IRAS 17163-3907 at 2 micron tracing milli-arcsecond scales. Lastly, we apply a 2D radiative transfer model to fit the dereddened photometry and the radial profiles of published diffraction limited VISIR images at 8.59um, 11.85um and 12.81um simultaneously, adopting a revised distance determination using the new Gaia measurements (DR2).
809. FTS high resolution of CoIII
ID:
ivo://CDS.VizieR/J/ApJS/223/12
Title:
FTS high resolution of CoIII
Short Name:
J/ApJS/223/12
Date:
21 Oct 2021
Publisher:
CDS
Description:
The spectrum of CoIII has been recorded in the region 1562-2564{AA} (64000cm^-1^-39000cm^-1^) by Fourier transform (FT) spectroscopy, and in the region 1317-2500{AA} (164000cm^-1^-40000cm^-1^) using a 10.7m grating spectrograph with phosphor image plate detectors. The spectrum was excited in a cobalt-neon Penning discharge lamp. We classified 514 CoIII lines measured using FT spectroscopy, the strongest having wavenumber uncertainties approaching 0.004cm^-1^ (approximately 0.2m{AA} at 2000{AA}, or 1 part in 10^7^), and 240 lines measured with grating spectroscopy with uncertainties between 5 and 10m{AA}. The wavelength calibration of 790 lines of Raassen & Orti Ortin (1984PhyBC.123..353R) and 87 lines from Shenstone (1960CaJPh..38..677S) has been revised and combined with our measurements to optimize the values of all but one of the 288 previously reported energy levels. Order of magnitude reductions in uncertainty for almost two-thirds of the 3d^6^4s and almost half of the 3d^6^4p revised energy levels are obtained. Ritz wavelengths have been calculated for an additional 100 forbidden lines. Eigenvector percentage compositions for the energy levels and predicted oscillator strengths have been calculated using the Cowan code.
810. Full spectroscopic data release of the SPT-GMOS
ID:
ivo://CDS.VizieR/J/ApJS/227/3
Title:
Full spectroscopic data release of the SPT-GMOS
Short Name:
J/ApJS/227/3
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of SPT-GMOS, a spectroscopic survey with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South. The targets of SPT-GMOS are galaxy clusters identified in the SPT-SZ survey, a millimeter-wave survey of 2500deg^2^ of the southern sky using the South Pole Telescope (SPT). Multi-object spectroscopic observations of 62 SPT-selected galaxy clusters were performed between 2011 January and 2015 December, yielding spectra with radial velocity measurements for 2595 sources. We identify 2243 of these sources as galaxies, and 352 as stars. Of the galaxies, we identify 1579 as members of SPT-SZ galaxy clusters. The primary goal of these observations was to obtain spectra of cluster member galaxies to estimate cluster redshifts and velocity dispersions. We describe the full spectroscopic data set and resulting data products, including galaxy redshifts, cluster redshifts, and velocity dispersions, and measurements of several well-known spectral indices for each galaxy: the equivalent width, W, of [OII]{lambda}{lambda}3727, 3729 and H-{delta}, and the 4000{AA} break strength, D4000. We use the spectral indices to classify galaxies by spectral type (i.e., passive, post-starburst, star-forming), and we match the spectra against photometric catalogs to characterize spectroscopically observed cluster members as a function of brightness (relative to m*). Finally, we report several new measurements of redshifts for ten bright, strongly lensed background galaxies in the cores of eight galaxy clusters. Combining the SPT-GMOS data set with previous spectroscopic follow-up of SPT-SZ galaxy clusters results in spectroscopic measurements for >100 clusters, or ~20% of the full SPT-SZ sample.

Limit your search

more »

more »

more »

more »