- ID:
- ivo://CDS.VizieR/J/A+A/652/A126
- Title:
- Spectroscopy of CH3OH in layered and mixed ices
- Short Name:
- J/A+A/652/A126
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The molecular composition of interstellar ice mantles is defined by gas-grain processes in molecular clouds, with the main components being H_2_O, CO, and CO_2_. Methanol (CH_3_OH) ice is detected towards the denser pre-stellar cores and star-forming regions, where large amounts of CO molecules freeze out and get hydrogenated on top of the icy grains. The thermal heating from nearby protostars can further change the ice structure and composition. Despite the several observations of icy features carried out towards molecular clouds and along the line of site of protostars, it is not yet clear if interstellar ices are mixed or if they have a layered structure. We aim to examine the effect of mixed and layered ice growth in dust grain mantle analogues, with specific focus on the position and shape of methanol infrared bands, so dedicated future observations could shed light on the structure of interstellar ices in different environments. Mixed and layered ice samples were deposited on a cold substrate kept at a temperature of 10K using a closed-cycle cryostat placed in a vacuum chamber. The spectroscopic features were analysed by Fourier transform infrared spectroscopy. Different proportions of the most abundant four molecular species in ice mantles, namely H_2_O, CO, CO_2_, and CH_3_OH, were investigated, with a special attention placed on the analysis of the CH_3_OH bands. We measure changes in the position and shape of the CH and CO stretching bands of CH_3_OH depending on the mixed or layered nature of the ice sample. Spectroscopic features of methanol are also found to change due to heating. A layered ice structure best reproduces the CH_3_OH band position recently observed towards a pre-stellar core and in star-forming regions. Based on our experimental results, we conclude that observations of CH_3_OH ice features in space can provide information about the structure of interstellar ices, and we expect the James Webb Space Telescope to put stringent constraints on the layered or mixed nature of ices in different interstellar environments, from molecular clouds to pre-stellar cores to protostars and protoplanetary discs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/other/BASI/39.517
- Title:
- Spectroscopy of classical Be stars
- Short Name:
- J/other/BASI/39.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic study of 150 Classical Be stars in 39 open clusters using medium resolution spectra in the wavelength range 3800-9000{AA}. One-third of the sample (48 stars in 18 clusters) has been studied for the first time. All these candidates were identified from an extensive survey of emission stars in young open clusters using slitless spectroscopy (Mathew et al., 2008MNRAS.388.1879M). This large data set covers CBe stars of various spectral types and ages found in different cluster environments in largely northern open clusters, and is used to study the spectral characteristics of CBe stars in cluster environments.
- ID:
- ivo://CDS.VizieR/J/ApJS/175/462
- Title:
- Spectroscopy of Coma early-type galaxies
- Short Name:
- J/ApJS/175/462
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The long-slit spectra obtained along the minor axis, offset major axis, and diagonal axis are presented for 12 E and S0 galaxies of the Coma Cluster drawn from a magnitude-limited sample studied before. The rotation curves, velocity dispersion profiles, and the H_3_ and H_4_ coefficients of the Hermite decomposition of the line-of-sight velocity distribution are derived. The radial profiles of the H{beta}, Mg, and Fe line strength indices are measured too. In addition, the surface photometry of the central regions of a subsample of four galaxies recently obtained with the Hubble Space Telescope is presented. The data will be used to construct dynamical models of the galaxies and study their stellar populations.
- ID:
- ivo://CDS.VizieR/J/A+A/395/753
- Title:
- Spectroscopy of Coma early-type galaxies. II.
- Short Name:
- J/A+A/395/753
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present minor axis, offset major axis and one diagonal long slit spectra for 10 E and S0 galaxies of the Coma cluster drawn from a magnitude-limited sample studied before. We derive rotation curves, velocity dispersion profiles and the H_3_ and H_4_ coefficients of the Hermite decomposition of the line of sight velocity distribution. Moreover, we derive the line index profiles of Mg, Fe and Hbeta line indices and assess their errors. The data will be used to construct dynamical models of the galaxies and study their stellar populations.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/121
- Title:
- Spectroscopy of comet C/2004 Q2 (Machholz)
- Short Name:
- J/ApJ/703/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed comet C/2004 Q2 (Machholz) with the Keck II telescope in late 2005 January and we obtained the spectra of C/2004 Q2 including many emission lines of volatile species such as H_2_O, HCN, C_2_H_2_, NH_3_, CH_4_, C_2_H_6_, CH_3_OH, and H_2_CO with high-signal-to-noise ratios. Based on our observations, we determined the mixing ratios of the molecules relative to H_2_O in C/2004 Q2. C/2004 Q2 might be the intermediate type between Oort Cloud and Jupiter Family comets. To investigate the formation conditions of such intermediate type comet, we focused on the (C_2_H_2_+C_2_H_6_)/H_2_O ratios and C_2_H_6_/(C_2_H_6_+C_2_H_2_) ratios in comets from the viewpoint of conversion from C_2_H_2_ to C_2_H_6_ in the precometary ices. We employed the dynamical-evolutional model and the chemical-evolutional model to determine the formation region of C/2004 Q2 more precisely. We found that comet C/2004 Q2 might have formed in relatively inner region of the solar nebula than the typical Oort Cloud comet (but slightly further than 5AU from the proto-Sun).
- ID:
- ivo://CDS.VizieR/J/A+A/549/A104
- Title:
- Spectroscopy of {delta} Scuti star KIC 5988140
- Short Name:
- J/A+A/549/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used high-quality Kepler photometry and spectroscopic data to investigate the Kepler binary candidate KIC 5988140. Using the spectrum synthesis method, we derived the fundamental parameters (T_eff_, logg, [M/H], vsini) and the abundances. Frequency analyses of both the photometric and the spectroscopic data revealed the same two dominant frequencies. We also detected in the photometry the signal of nine more, significant frequencies located in the range 10-15c/d. The light and radial velocity curves follow a similar, stable double-wave pattern. We considered three different scenarios: binarity, co-existence of Gamma Doradus and Delta Scuti pulsations and rotational modulation. We confirm the occurrence of various independent Delta Scuti-type pressure modes in the Kepler light curve. However, we argue that the physical cause of low frequencies in the light and radial velocity variations of this late A-type star remain unexplained by any of the presently considered scenarios.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A49
- Title:
- Spectroscopy of dwarf stars
- Short Name:
- J/A+A/628/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New space missions, such as NASA TESS or ESA PLATO, will focus on bright stars, which have been largely ignored by modern large surveys, especially in the northern sky. Spectroscopic information is of paramount importance in characterising the stars and analysing planets possibly orbiting them, and in studying the Galactic disc evolution. The aim of this work was to analyse all bright (V<8mag) F, G, and K dwarf stars using high-resolution spectra in the selected sky fields near the northern celestial pole. The observations were carried out with the 1.65m diameter telescope at the Molttai Astronomical Observatory and a fibre-fed high-resolution spectrograph covering a full visible wavelength range (4000-8500{AA}). The atmospheric parameters were derived using the classical equivalent width approach while the individual chemical element abundances were determined from spectral synthesis. For both tasks the one-dimensional plane-parallel LTE MARCS stellar model atmospheres were applied. Results. We determined the main atmospheric parameters, kinematic properties, orbital parameters, and stellar ages for 109 newly observed stars and chemical abundances of 23 chemical species for 249 F, G, and K dwarf stars observed in the present study and in our previous study. The [MgI/FeI] ratio was adopted to define the thin-disc ({alpha}-poor) and thick-disc ({alpha}-rich) stars in our sample. We explored the behaviour of 21 chemical species in the [El/FeI] versus [FeI/H] and [El/FeI] versus age planes, and compared the results with the latest Galactic chemical evolution models. We also explored [El/FeI] gradients according to the mean Galactocentric distances and maximum height above the Galactic plane.
- ID:
- ivo://CDS.VizieR/J/MNRAS/276/1341
- Title:
- Spectroscopy of E and S0 galaxies
- Short Name:
- J/MNRAS/276/1341
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Central velocity dispersions, Mg_2_ line indices, and radial velocities for 220 E and S0 galaxies are derived on basis of intermediate resolution spectroscopy. Galaxies in the following clusters have been observed: Abell 194, Abell 539, Abell 3381, Abell 3574, S639, S753, Doradus, HydraI (Abell 1060), and Grm15. The spectra cover 50 or 100nm centered on the magnesium triplet at 517.7nm. In this catalog we give the mean values of the parameters. The central velocity dispersion and the Mg_2_ line indices have been aperture corrected to a circular aperture with a diameter of 1.19h^-1^kpc, equivalent to 3.4arcsec at the distance of the Coma cluster. Values are also given for a circular aperture with radius equal to the effective radius of the galaxy (cf. Jorgensen et al. 1995, Cat. J/MNRAS/273/1097). The Mg_2_ indices are consistent with the Lick system. The typical uncertainty of the central velocity dispersion is 0.036 in log({sigma}), the typical uncertainty of Mg_2_ is 0.013. Further, literature data (velocity dispersions and Mg_2_ indices) for the clusters A194, DC2345-28 and Coma (A1656) have been brought on a homogeneous system and aperture corrected to the aperture sizes given above. The literature data are from Davies et al. (1987ApJS...64..581D), Dressler (1987ApJ...317....1D), Dressler & Shectman 1988 (J/AJ/95/284), Lucey & Carter (1988MNRAS.235.1177L), Lucey et al. (1991MNRAS.253..584L), and Guzman et al. (1992MNRAS.257..187G).
- ID:
- ivo://CDS.VizieR/J/AJ/144/78
- Title:
- Spectroscopy of early-type galaxies in A262
- Short Name:
- J/AJ/144/78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new radially resolved spectroscopy of eight early-type galaxies in the A262 cluster. The measurements include stellar rotation, velocity dispersion, H_3_ and H_4_coefficients of the line-of-sight velocity distribution along the major and minor axes and an intermediate axis as well as line-strength index profiles of Mg, Fe, and H{beta}. The ionized-gas velocity and velocity dispersion is measured for six sample galaxies along different axes. We derive dynamical mass-to-light ratios and dark matter densities from orbit-based dynamical models, complemented by the galaxies' ages, metallicities, and {alpha}-element abundances from single stellar-population models. The ionized-gas kinematics give a valuable consistency check for the model assumptions about orientation and intrinsic shape of the galaxies. Four galaxies have a significant detection of dark matter and their halos are about 10 times denser than in spirals of the same stellar mass. By calibrating dark matter densities to cosmological simulations we find assembly redshifts of z_DM_{approx}1-3, as previously reported for the Coma Cluster. The dynamical mass that follows the light is larger than expected for a Kroupa stellar initial mass function (IMF), especially in galaxies with high velocity dispersion {sigma}_eff_ inside the effective radius r_eff_. This could indicate a "massive" IMF in massive galaxies. Alternatively, some of the dark matter in massive galaxies could follow the light very closely. In combination with our comparison sample of Coma early-type galaxies, we now have 5 of 24 galaxies where (1) mass follows light to 1-3r_eff_, (2) the dynamical mass-to-light ratio of all the mass that follows the light is large ({approx}8-10 in the Kron-Cousins R band), and (3) the dark matter fraction is negligible to 1-3r_eff_. Unless the IMF in these galaxies is particularly "massive" and somehow coupled to the dark matter content, there seems to be a significant degeneracy between luminous and dark matter in at least some early-type galaxies. The role of violent relaxation is briefly discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/146/10
- Title:
- Spectroscopy of 120 emission-line ICRF2 candidates
- Short Name:
- J/AJ/146/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Continuing our program of spectroscopic observations of International Celestial Reference Frame (ICRF) sources, we present redshifts for 120 quasars and radio galaxies. Data were obtained with five telescopes: the 3.58m European Southern Observatory New Technology Telescope, the two 8.2m Gemini telescopes, the 2.5m Nordic Optical Telescope (NOT), and the 6.0m Big Azimuthal Telescope of the Special Astrophysical Observatory in Russia. The targets were selected from the International VLBI Service for Geodesy & Astrometry candidate International Celestial Reference Catalog which forms part of an observational very long baseline interferometry (VLBI) program to strengthen the celestial reference frame. We obtained spectra of the potential optical counterparts of more than 150 compact flat-spectrum radio sources, and measured redshifts of 120 emission-line objects, together with 19 BL Lac objects. These identifications add significantly to the precise radio-optical frame tie to be undertaken by Gaia, due to be launched in 2013, and to the existing data available for analyzing source proper motions over the celestial sphere. We show that the distribution of redshifts for ICRF sources is consistent with the much larger sample drawn from Faint Images of the Radio Sky at Twenty cm (FIRST) and Sloan Digital Sky Survey, implying that the ultra-compact VLBI sources are not distinguished from the overall radio-loud quasar population. In addition, we obtained NOT spectra for five radio sources from the FIRST and NRAO VLA Sky Survey catalogs, selected on the basis of their red colors, which yielded three quasars with z>4.
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