- ID:
- ivo://CDS.VizieR/J/ApJ/755/90
- Title:
- [NeII] emission line observations from SgrA West
- Short Name:
- J/ApJ/755/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new observations of the [NeII] emission from the ionized gas in Sgr A West with improved resolution and sensitivity. About half of the emission comes from gas with kinematics indicating it is orbiting in a plane tipped about 25{deg} from the Galactic plane. This plane is consistent with that derived previously for the circumnuclear molecular disk and the northern arm and western arc ionized features. However, unlike most previous studies, we conclude that the ionized gas is not moving along the ionized features, but on more nearly circular paths. The observed speeds are close to, but probably somewhat less than expected for orbital motions in the potential of the central black hole and stars and have a small inward component. The spatial distribution of the emission is well fitted by a spiral pattern. We discuss possible physical explanations for the spatial distribution and kinematics of the ionized gas, and conclude that both may be best explained by a one-armed spiral density wave, which also accounts for both the observed low velocities and the inward velocity component. We suggest that a density wave may result from the precession of elliptical orbits in the potential of the black hole and stellar mass distribution.
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- ID:
- ivo://CDS.VizieR/J/A+A/542/A110
- Title:
- Neutral gas in the Milky Way halo
- Short Name:
- J/A+A/542/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an absorption-selected survey of CaII and NaI features located in the halo of the Milky Way using QSO absorption spectroscopy. We made use of the ESO data archive and retrieved all publically available absorption-line data for low- and high-redshift QSOs observed with the Ultraviolet and Visual Echelle Spectrograph (UVES) on the VLT. This enormous data archive (Spectral Quasar Absorption Database, SQUAD; PI: M.T. Murphy) provides high-quality spectral data for ~400 quasars and active galactic nuclei (AGN). Most of these spectra were taken in the UVES standard configuration using the 1" slit, providing a spectral resolution of R~45000 (corresponding to a velocity resolution of ~6.6km/sFWHM). The spectral coverage as well as the signal-to-noise ratio (S/N) varies substantially among the spectra, reflecting the various scientific goals of the original proposals. For several of the sight lines we performed deep (brightness temperature limit, Tb_lim_~30mK, angular resolution: 9' FWHM, spectral resolution: 0.5km/s FWHM) follow-up radio observations using the Effelsberg 100-m telescope to search for HI emission. Furthermore for a large fraction of the sight lines we obtained HI data from the new Galactic All-Sky survey (GASS, Tb_lim_~60mK, angular resolution: 15.6' FWHM, spectral resolution: 0.8km/s FWHM) and the Effelsberg-Bonn HI survey (EBHIS, Tb_lim_~90mK, angular resolution: 10.5' FWHM, spectral resolution: 1.2km/s FWHM). All HI data were corrected for stray radiation using software by P. Kalberla.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A125
- Title:
- Neutron-capture elements abundances in Cepheids
- Short Name:
- J/A+A/586/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new accurate abundances for five neutron-capture (Y, La, Ce, Nd, Eu) elements in 73 classical Cepheids located across the Galactic thin disk. Individual abundances are based on high spectral resolution (R~38000) and high signal-to-noise ratio (S/N~50-300) spectra collected with UVES at ESO VLT for the DIONYSOS project. Taking account for similar Cepheid abundances provided either by our group (111 stars) or available in the literature, we end up with a sample of 435 Cepheids covering a broad range in iron abundances (-1.6<[Fe/H]<0.6). We found, using homogeneous individual distances and abundance scales, well defined gradients for the above elements. However, the slope of the light s-process element (Y) is at least a factor of two steeper than the slopes of heavy s- (La, Ce, Nd) and r- (Eu) process elements. The s to r abundance ratio ([La/Eu]) of Cepheids shows a well defined anticorrelation with of both Eu and Fe. On the other hand, Galactic field stars attain an almost constant value and only when they approach solar iron abundance display a mild enhancement in La. The [Y/Eu] ratio shows a mild evidence of a correlation with Eu and, in particular, with iron abundance for field Galactic stars. We also investigated the s-process index -- [hs/ls] -- and we found a well defined anticorrelation, as expected, between [La/Y] and iron abundance. Moreover, we found a strong correlation between [La/Y] and [La/Fe] and, in particular, a clear separation between Galactic and Sagittarius red giants. Finally, the comparison between predictions for low-mass asymptotic giant branch stars and the observed [La/Y] ratio indicate a very good agreement over the entire metallicity range covered by Cepheids. However, the observed spread, at fixed iron content, is larger than predicted by current models.
- ID:
- ivo://CDS.VizieR/J/AZh/81/209
- Title:
- Neutron capture elements in stars: neodymium
- Short Name:
- J/AZh/81/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived the LTE neodymium abundances in 60 cool stars with [Fe/H] from 0.25 to -1.71 by applying a synthetic-spectrum analysis to spectroscopic observations of NdII lines with a resolution of {lambda}/{Delta}{lambda}~60000 and signal-to noise ratios of 100-200.
- ID:
- ivo://CDS.VizieR/J/ApJ/769/95
- Title:
- [NeV] or [NeIII] double peaked SDSS quasars
- Short Name:
- J/ApJ/769/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 131 quasars from the Sloan Digital Sky Survey at redshifts 0.8<z<1.6 with double peaks in either of the high-ionization narrow emission lines [NeV]{lambda}3426 or [NeIII]{lambda}3869. These sources were selected with the intention of identifying high-redshift analogs of the z<0.8 active galactic nuclei (AGNs) with double-peaked [OIII]{lambda}5007 lines, which might represent AGN outflows or dual AGNs. Lines of high ionization potential are believed to originate in the inner, highly photoionized portion of the narrow line region, and we exploit this assumption to investigate the possible kinematic origins of the double-peaked lines. For comparison, we measure the [NeV]{lambda}3426 and [NeIII]{lambda}3869 double peaks in low-redshift (z<0.8) [OIII]-selected sources. We find that [NeV]{lambda}3426 and [NeIII]{lambda}3869 show a correlation between line splitting and line width similar to that of [OIII]{lambda}5007 in other studies, and the velocity splittings are correlated with the quasar Eddington ratio. These results suggest an outflow origin for at least a subset of the double peaks, allowing us to study the high-ionization gas kinematics around quasars. However, we find that a non-negligible fraction of our sample show no evidence for an ionization stratification. For these sources, the outflow scenario is less compelling, leaving the dual AGN scenario as a viable possibility. Finally, we find that our sample shows an anti-correlation between the velocity-offset ratio and luminosity ratio of the components, which is a potential dynamical argument for the presence of dual AGNs. Therefore, this study serves as a first attempt at extending the selection of candidate dual AGNs to higher redshifts.
- ID:
- ivo://CDS.VizieR/J/A+A/520/A57
- Title:
- New FeII energy levels from stellar spectra
- Short Name:
- J/A+A/520/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectra of B-type and early A-type stars show numerous unidentified lines in the whole optical range, especially in the 5100-5400{AA} interval. Because FeII transitions to high energy levels should be observed in this region, we used semiempirical predicted wavelengths and gf-values of FeII to identify unknown lines. Semiempirical line data for FeII computed by Kurucz are used to synthesize the spectrum of the slow-rotating, Fe - overabundant CP star HR6000.
- ID:
- ivo://CDS.VizieR/J/ApJS/216/1
- Title:
- New FeI level energies from stellar spectra
- Short Name:
- J/ApJS/216/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectrum of the Fe I atom is critical to many areas of astrophysics and beyond. Measurements of the energies of its high-lying levels remain woefully incomplete, however, despite extensive laboratory and solar analysis. In this work, we use high-resolution archival absorption-line ultraviolet and optical spectra of stars whose warm temperatures favor moderate Fe I excitation. We derive the energy for a particular upper level in Kurucz's semiempirical calculations by adopting a trial value that yields the same wavelength for a given line predicted to be about as strong as that of a strong unidentified spectral line observed in the stellar spectra, then checking the new wavelengths of other strong predicted transitions that share the same upper level for coincidence with other strong observed unidentified lines. To date, this analysis has provided the upper energies of 66 Fe I levels. Many new energy levels are higher than those accessible to laboratory experiments; several exceed the Fe I ionization energy. These levels provide new identifications for over 2000 potentially detectable lines. Almost all of the new levels of odd parity include UV lines that were detected but unclassified in laboratory Fe I absorption spectra, providing an external check on the energy values. We motivate and present the procedure, provide the resulting new energy levels and their uncertainties, list all the potentially detectable UV and optical new Fe I line identifications and their gf values, point out new lines of astrophysical interest, and discuss the prospects for additional Fe I energy level determinations.
- ID:
- ivo://CDS.VizieR/J/ApJS/229/23
- Title:
- New FeI level energies from stellar spectra. II.
- Short Name:
- J/ApJS/229/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Fe I spectrum is critical to many areas of astrophysics, yet many of the high-lying levels remain uncharacterized. To remedy this deficiency, Peterson & Kurucz (2015, J/ApJS/216/1) identified Fe I lines in archival ultraviolet and optical spectra of metal-poor stars, whose warm temperatures favor moderate Fe I excitation. Sixty-five new levels were recovered, with 1500 detectable lines, including several bound levels in the ionization continuum of Fe I. Here, we extend the previous work by identifying 59 additional levels, with 1400 detectable lines, by incorporating new high-resolution UV spectra of warm metal-poor stars recently obtained by the Hubble Space Telescope Imaging Spectrograph. We provide gf values for these transitions, both computed as well as adjusted to fit the stellar spectra. We also expand our spectral calculations to the infrared, confirming three levels by matching high-quality spectra of the Sun and two cool stars in the H-band. The predicted gf values suggest that an additional 3700 Fe I lines should be detectable in existing solar infrared spectra. Extending the empirical line identification work to the infrared would help confirm additional Fe I levels, as would new high-resolution UV spectra of metal-poor turnoff stars below 1900{AA}.
- ID:
- ivo://CDS.VizieR/J/ApJS/184/133
- Title:
- New ground-state measurements of ethyl cyanide
- Short Name:
- J/ApJS/184/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectrum of ethyl cyanide, or propionitrile (CH_3_CH_2_CN), has been repeatedly observed in the interstellar medium with large column densities and surprisingly high temperatures in hot core sources. The construction of new, more sensitive, observatories accessing higher frequencies such as Herschel, ALMA, and SOFIA have made it important to extend the laboratory data for ethyl cyanide to coincide with the capabilities of the new instruments. We report extensions of the laboratory measurements of the rotational spectrum of ethyl cyanide in its ground vibrational state to 1.6THz. A global analysis of the ground state, which includes all of the previous data and 3356 newly assigned transitions, has been fitted to within experimental error to J=132, K=36, using both Watson A-reduced and Watson S-reduced Hamiltonians.
- ID:
- ivo://CDS.VizieR/J/AJ/125/1598
- Title:
- New high proper motion stars in the northern sky
- Short Name:
- J/AJ/125/1598
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We define an enhanced spectral classification scheme for M dwarf stars and use it to derive spectral classification of 104 northern stars with proper motions larger than 0.5"/yr that we discovered in a survey of high proper motion stars at low Galactic latitudes. The final tally is as follows: 54 M dwarfs, 25 sdK and sdM subdwarfs, 14 esdK and esdM extreme subdwarfs, and 11 DA and DC white dwarfs. Among the most interesting cases, we find one star to be the coolest subdwarf ever reported (LSR 2036+5059, with spectral type sdM7.5), a new M9.0 dwarf only about 6 pc distant (LSR 1835+3259), and a new M6.5 dwarf only 7 pc from the Sun (LSR 2124+4003). Spectroscopic distances suggests that 27 of the M dwarfs, three of the white dwarfs, and one of the subdwarfs (LSR 2036+5059) are within 25 pc of the Sun, making them excellent candidates for inclusion in the solar neighborhood census. Estimated sky-projected velocities suggest that most of our subdwarfs and extreme subdwarfs have halo kinematics. We find that several white dwarfs and nonmetal-poor M dwarfs also have kinematics consistent with the halo, and we briefly discuss their possible origin.
