- ID:
- ivo://CDS.VizieR/J/A+A/654/A143
- Title:
- Ion and femtosecond laser irradiation spectra
- Short Name:
- J/A+A/654/A143
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Space weathering is a process that changes the surface of airless planetary bodies. Prime space weathering agents are solar wind irradiation and micrometeoroid bombardment. These processes alter planetary reflectance spectra and often modify their compositional diagnostic features. In this work we focused on simulating and comparing the spectral changes caused by solar wind irradiation and by micrometeoroid bombardment to gain a better understanding of these individual space weathering processes. We used olivine and pyroxene pellets as proxies for planetary materials. To simulate solar wind irradiation we used hydrogen, helium, and argon ions with energies from 5 to 40keV and fluences of up to 10^18^particles/cm^2^. To simulate micrometeoroid bombardment we used individual femtosecond laser pulses. We analysed the corresponding evolution of different spectral parameters, which we determined by applying the Modified Gaussian Model, and we also conducted principal component analysis. The original mineralogy of the surface influences the spectral evolution more than the weathering agent, as seen from the diverse evolution of the spectral slope of olivine and pyroxene upon irradiation. The spectral slope changes seen in olivine are consistent with observations of A-type asteroids, while the moderate to no slope changes observed in pyroxene are consistent with asteroid (4) Vesta. We also observed some differences in the spectral effects induced by the two weathering agents. Ions simulating solar wind have a smaller influence on longer wavelengths of the spectra than laser irradiation simulating micrometeoroid impacts. This is most likely due to the different penetration depths of ions and laser pulses. Our results suggest that in some instances it might be possible to distinguish between the contributions of the two agents on a weathered surface.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/407/2475
- Title:
- Ionized gas in E/S0 galaxies with dust lanes
- Short Name:
- J/MNRAS/407/2475
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of multicolour observations of 30 E/S0 galaxies with dust lanes. For each galaxy we obtained broad-band images and narrow-band images using interference filters isolating the H{alpha}+[NII] emission lines to derive the amount and morphology of dust and ionized gas. To improve the wavelength coverage we retrieved data from the Sloan Digital Sky Survey and Two Micron All Sky Survey and combined these with our data. Ionized gas is detected in 25 galaxies and shows in most cases a smooth morphology, although knots and filamentary structure are also observed in some objects.
- ID:
- ivo://CDS.VizieR/J/A+AS/120/257
- Title:
- Ionized gas velocity in 6 galaxies
- Short Name:
- J/A+AS/120/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report observations of the velocity field of the ionized gas in the nearby ellipticals NGC 1453, NGC 2974, NGC 3962, NGC 4636, NGC 6868 and NGC 7097. This is part of an ESO Key Programme intended to derive the mass distribution of elliptical galaxies and to investigate the possible presence of dark matter. All galaxy spectra are characterized by LINER-type emission. The derived gas kinematics confirm the picture of a regular gaseous disk structure with ordered rotation. The gas velocity dispersion profiles decline rapidly from a high central value in the range of =~150 to =~250km/s.
- ID:
- ivo://CDS.VizieR/J/ApJ/510/104
- Title:
- Ionizing Stars of Extragalactic H II Regions
- Short Name:
- J/ApJ/510/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Medium-resolution spectra from 3650 to 10000 {AA} are presented for 96 giant H II regions distributed in 20 spiral galaxies. In order to interpret the data, we have calculated two separate grids of photoionization models, adopting single-star atmospheres (Kurucz) and star clusters synthesized with different initial mass functions (IMFs) as ionizing sources. Additional models were computed with more recent non-LTE stellar atmospheres, in order to check the effects of different stellar ionizing fluxes. We use the radiation softness parameter {eta}'=([O II]/[O III])/([S II]/[S III]) of Vilchez & Pagel (1988MNRAS.231..257V) to test for a metallicity dependence of the effective temperatures of the ionizing stars. Our results are consistent with a significant decrease in mean stellar temperatures of the ionizing stars with increasing metallicity. The magnitude of the effect, combined with the behavior of the He I {lambda}5876/H{beta} ratio, suggest a smaller upper mass limit for star formation at abundances higher than solar, even when considering the effects of metallicity on stellar evolution and atmospheric line blanketing. However, the exact magnitudes of the stellar temperature and IMF variations are dependent on the choice of stellar atmosphere and evolution models used, as well as on uncertainties in the nebular abundance scale at high metallicities. Our results also constrain the systematic behavior of the ionization parameter and the N/O ratio in extragalactic H II regions. The observed spectral sequences are inconsistent with current stellar evolution models, which predict a luminous, hot W-R stellar population in evolved H II regions older than 2-3 Myr. This suggests either that the hardness of the emitted Lyman continuum spectrum has been overestimated in the models or that some mechanism disrupts the H II regions before the W-R phases become important.
- ID:
- ivo://CDS.VizieR/J/AJ/159/216
- Title:
- Ions density in the CGM of low mass galaxy groups
- Short Name:
- J/AJ/159/216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore how environment affects the metallicity of the circumgalactic medium (CGM) using 13 low-mass galaxy groups (two to five galaxies) at <z_abs_>=0.25 identified near background quasars. Using quasar spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph (HST/COS) and from Keck/High Resolution Echelle Spectrometer (Keck/HIRES) or the Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph (VLT/UVES), we measure column densities of or determine limits on CGM absorption lines. We use a Markov Chain Monte Carlo approach with Cloudy to estimate metallicities of cool (T~104K) CGM gas within groups and compare them to CGM metallicities of 47 isolated galaxies. Both group and isolated CGM metallicities span a wide range (-2<[Si/H]<0), where the mean group (-0.54{pm}0.22) and isolated (-0.77{pm}0.14) CGM metallicities are similar. Group and isolated environments have similar distributions of HI column densities as a function of impact parameter. However, contrary to isolated galaxies, we do not find an anticorrelation between HI column density and the nearest group galaxy impact parameter. We additionally divided the groups by member luminosity ratios (i.e., galaxy-galaxy and galaxy-dwarf groups). While there was no significant difference in their mean metallicities, a modest increase in sample size should allow one to statistically identify a higher CGM metallicity in galaxy-dwarf groups compared to galaxy-galaxy groups. We conclude that either environmental effects have not played an important role in the metallicity of the CGM at this stage and expect that this may only occur when galaxies are strongly interacting or merging or that some isolated galaxies have higher CGM metallicities due to past interactions. Thus, environment does not seem to be the cause of the CGM metallicity bimodality.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/6
- Title:
- IR absorbance spectra of CH4, C2H6, C3H8 & C4H10
- Short Name:
- J/ApJS/234/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The only known phosphorus-containing organic compounds of extraterrestrial origin, alkylphosphonic acids, were discovered in the Murchison meteorite and have accelerated the hypothesis that reduced oxidation states of phosphorus were delivered to early Earth and served as a prebiotic source of phosphorus. While previous studies looking into the formation of these alkylphosphonic acids have focused on the iron-nickel phosphide mineral schreibersite and phosphorous acid as a source of phosphorus, this work utilizes phosphine (PH3), which has been discovered in the circumstellar envelope of IRC +10216, in the atmosphere of Jupiter and Saturn, and believed to be the phosphorus carrier in comet 67P/Churyumov-Gerasimenko. Phosphine ices prepared with interstellar molecules such as carbon dioxide, water, and methane were subjected to electron irradiation, which simulates the secondary electrons produced from galactic cosmic rays penetrating the ice, and probed using infrared spectroscopy to understand the possible formation of alkylphosphonic acids and their precursors on interstellar icy grains that could become incorporated into meteorites such as Murchison. We present the first study and results on the possible synthesis of alkylphosphonic acids produced from phosphine-mixed ices under interstellar conditions. All functional groups of alkylphosphonic acids were detected through infrared spectroscopically, suggesting that this class of molecules can be formed in interstellar ices.
- ID:
- ivo://CDS.VizieR/J/MNRAS/406/460
- Title:
- IR absorbance spectra of olivine
- Short Name:
- J/MNRAS/406/460
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Laboratory measurements quantifying the effect of Fe substituting for Mg in olivine are needed to distinguish compositional from temperature, grain size and grain shape effects in observational data. To address this need, we study room temperature absorption spectra of a large suite of olivines evenly spaced across Mg and Fe compositions. We apply the principle that classical dispersion theory may be used to determine peak positions as well as peak widths, strengths and possibly optical function (n({lambda}) and k({lambda})) estimates from absorption spectra of thin film samples of these olivines and two additional isotropic and anisotropic minerals with varying hardness and numbers of spectral bands. For olivine, we find that this method provides good estimates of peak position and that accounting for asymmetric peak shapes in this way increases the error on full width at half-maximum and oscillator strengths. Values from classical dispersion fits better match published n and k derived from reflectivity of single crystals when the dust proxy is soft and the thickness of the sample is independently constrained. Electronic data and peak parameter trends for the laboratory olivine absorption spectra and the viability of the extracted n and k are discussed with regard to astronomy.
- ID:
- ivo://CDS.VizieR/J/A+A/563/A97
- Title:
- IRAM 30m reduced spectra of 59 sources
- Short Name:
- J/A+A/563/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Understanding the chemical evolution of young (high-mass) star-forming regions is a central topic in star formation research. Chemistry is employed as a unique tool 1) to investigate the underlying physical processes and 2) to characterize the evolution of the chemical composition. With these aims in mind, we observed a sample of 59 high-mass star-forming regions at different evolutionary stages varying from the early starless phase of infrared dark clouds to high-mass protostellar objects to hot molecular cores and, finally, ultra-compact HII regions at 1mm and 3mm with the IRAM 30m telescope. We determined their large-scale chemical abundances and found that the chemical composition evolves along with the evolutionary stages.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A137
- Title:
- IRAS 16293-2422 CH_3_CCH spectral cubes
- Short Name:
- J/A+A/631/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Propyne (CH_3_CCH) has been detected in a variety of environments, from Galactic star-forming regions to extragalactic sources. Such molecules are excellent tracers of the physical conditions in star-forming regions. This study explores the emission of CH_3_CCH in the low-mass protostellar binary, IRAS 16293-2422, examining the spatial scales traced by this molecule, as well as its formation and destruction pathways. ALMA observations from the Protostellar Interferometric Line Survey (PILS) are used to determine the abundances and excitation temperatures of CH_3_CCH towards both protostars, exploring spatial scales from 70 to 2400au. The three-phase chemical kinetics model MAGICKAL is also used, to explore the chemical reactions of this molecule. CH_3_CCH is detected towards both IRAS 16293A and IRAS 16293B and is found to trace the hot corino component around each source in the PILS dataset. Eighteen transitions above 3{sigma} are detected, enabling robust excitation temperatures and column densities to be determined in each source. In IRAS 16293A, an excitation temperature of 90K and a column density of 7.8x10^15^cm^-2^ best fits the spectra. In IRAS 16293B, an excitation temperature of 100K and 6.8x10^15^cm^-2^ best fits the spectra. The chemical modelling finds that in order to reproduce the observed abundances, both gas-phase and grain-surface reactions are needed. CH_3_CCH is a molecule whose brightness and abundance in many different regions can be utilised to provide a benchmark of molecular variation with the physical properties of star-forming regions. It is essential when making such comparisons, that the abundances are determined with a good understanding of the spatial scale of the emitting region, to ensure that accurate abundances are derived
- ID:
- ivo://CDS.VizieR/J/MNRAS/276/57
- Title:
- IRAS Galactic star-forming regions. II.
- Short Name:
- J/MNRAS/276/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of the analysis of the occurrence of 22.2-GHz H_2_O maser emission in a sample of 1409 IRAS sources north of declination -30deg associated with star-forming regions are presented. Our sample contains all the IRAS sources that satisfy Emerson criteria for selecting molecular cores associated with the earliest evolutionary stages of the star-forming process. In a previous paper (Paper I, 1994MNRAS.266..123P), we have reported the results of the observations of about one third of the sample. In the present paper the observations of the remaining IRAS sources are presented: 18 of them are newly detected maser sources. The results show that 20 per cent of all IRAS sources that satisfy the Wood & Churchwell criteria have H2O water masers. This is in agreement with the assumption that these criteria select objects that are connected with the early phases of the evolution of high-mass star-forming regions. Moreover, about one third of the whole sample selected according to Emerson criteria contains IRAS sources that are not associated with massive star-forming processes, but probably with molecular cores in low-mass star-forming regions.
