- ID:
- ivo://CDS.VizieR/J/A+A/632/A55
- Title:
- Line list from Pal 13 sample stars
- Short Name:
- J/A+A/632/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At a Galactocentric distance of 27kpc, Palomar 13 is an old globular cluster (GC) belonging to the outer halo. We present a chemical abundance analysis of this remote system from high-resolution spectra obtained with the Keck/HIRES spectrograph. Owing to the low signal-to-noise ratio of the data, our analysis is based on a coaddition of the spectra of 18 member stars. We are able to determine integrated abundance ratios for 16 species of 14 elements, of {alpha}-elements (Mg, Si, Ca, and Ti), Fe-peak (Sc, Mn, Cr, Ni, Cu, and Zn), and neutron-capture elements (Y and Ba). While the mean Na abundance is found to be slightly enhanced and halo-like, our method does not allow us to probe an abundance spread that would be expected in this light element if multiple populations are present in Pal 13. We find a metal-poor mean metallicity of -1.91+/-0.05 (statistical) +/-0.22 (systematic), confirming that Pal 13 is a typical metal-poor representative of the outer halo. While there are some differences between individual {alpha}-elements, such as halo-like Mg and Si versus the mildly lower Ca and Ti abundances, the mean [{alpha}/Fe] of 0.34+/-0.06 is consistent with the marginally lower {alpha} component of the halo field and GC stars at similar metallicity. We discuss our results in the context of other objects in the outer halo and consider which of these objects were likely accreted. We also discuss the properties of their progenitors. While chemically, Pal 13 is similar to Gaia-Enceladus and some of its GCs, this is not supported by its kinematic properties within the Milky Way system. Moreover, its chemodynamical similarity with NGC 5466, a purported progeny of the Sequoia accretion event, might indicate a common origin in this progenitor. However, the ambiguities in the full abundance space of this comparison emphasize the difficulties in unequivocally labeling a single GC as an accreted object, let alone assigning it to a single progenitor.
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- ID:
- ivo://CDS.VizieR/J/ApJ/873/L5
- Title:
- Magnetic field measurements of Ap/Bp stars
- Short Name:
- J/ApJ/873/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on magnetic field measurements of 157 chemically peculiar A/B stars (Ap/Bp) based on resolved, magnetically split absorption lines present in H-band spectra provided by the Sloan Digital Sky Survey (SDSS)/Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. These stars represent the extreme magnetic end of a still-growing sample of >900 Ap/Bp stars selected among the APOGEE telluric standard stars as those with CeIII absorption lines and/or literature Ap/Bp classifications. The lines most frequently resolved into their split components for these stars in the H-band pertain primarily pertain to CeIII, CrII, FeI, MnII, SiI, and CaII, in addition to one or more unidentified ions. Using mean magnetic field modulus (<B>) estimates for transitions with known Lande factors, we estimate effective Lande factors for 5 CeIII lines and 15 unknown lines and proceed to measure <B> of 157 stars, only 3 of which have previous literature estimates of <B>. This 183% increase in the number of Ap/Bp stars for which <B> has been measured is a result of the large number of stars observed by SDSS/APOGEE, extension of high-resolution Ap/Bp star observations to fainter magnitudes, and the advantages of long wavelengths for resolving magnetically split lines. With <B>~25kG, the star 2MASS J02563098+4534239 is currently the most magnetic star of the SDSS/APOGEE sample. Effective Lande factors, representative line profiles, and magnetic field moduli are presented. The validity of the results is supported using optical, high-resolution, follow-up spectra for 29 of the stars.
- 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/ApJ/880/138
- Title:
- Observed transitions of CH_3_OH and CH_3_CHO
- Short Name:
- J/ApJ/880/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IRAM 30m Observations toward eight protostellar outflow sources were taken in the 96-176GHz range. Transitions of CH_3_OH and CH_3_CHO were detected in seven of them. The integrated emissions of the transitions of each species that fell into the observed frequency range were measured and fit using RADEX and LTE models. Column densities and gas properties inferred from this fitting are presented. The ratio of the A and E-type isomers of CH_3_OH indicates that the methanol observed in these outflows was formed on the grain surface. Both species demonstrate a reduction of terminal velocity in their line profiles in faster outflows, indicating destruction in the post-shock gas phase. This destruction, and a near constant ratio of the CH_3_OH and CH_3_CHO column densities, imply it is most likely that CH_3_CHO also forms on the grain surface.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/119
- Title:
- Properties of the highly ionized gas of quasars
- Short Name:
- J/ApJ/788/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from our NASA Keck Observatory Database of Ionized Absorbers toward Quasars (KODIAQ) survey which aims to characterize the properties of the highly ionized gas of galaxies and their circumgalactic medium (CGM) at 2<z<4. We select absorbers optically thick at the Lyman limit ({tau}_LL_>1, logN_HI_>17.3}) as probes of these galaxies and their CGM where both transitions of the O VI doublet have little contamination from the Ly{alpha}, {beta} forests. We found 20 absorbers that satisfy these rules: 7 Lyman limit systems (LLSs), 8 super-LLSs (SLLSs) and 5 damped Ly{alpha} (DLAs). The O VI detection rate is 100% for the DLAs, 71% for the LLSs, and 63% for the SLLSs. When O VI is detected, log(N_O VI_)=14.9+/-0.3, an average O VI column density substantially larger and with a smaller dispersion than found in blind O VI surveys at similar redshifts. Strong O VI absorption is therefore nearly ubiquitous in the CGM of z~2-3 galaxies. The total velocity widths of the O VI profiles are also large (200<={Delta}_{upsilon}_O VI_<=400 km/s). These properties are quite similar to those seen for O VI in low-z star-forming galaxies, and therefore we hypothesize that these strong CGM O VI absorbers (with {tau}_LL_>1) at 2<z<~3.5 also probe outflows of star-forming galaxies. The LLSs and SLLSs with no O VI absorption have properties consistent with those seen in cosmological simulations tracing cold streams feeding galaxies. When the highly ionized (Si IV and O VI) gas is taken into account, we determine that the {tau}_LL_>1 absorbers could contain as much as 3%-14% of the cosmic baryon budget at z~2-3, only second to the Ly{alpha} forest. We conservatively show that 5%-20% of the metals ever produced at z~2-3 are in form of highly ionized metals ejected in the CGM of galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A118
- Title:
- Vanadium measurements for 135 M dwarfs
- Short Name:
- J/A+A/654/A118
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- M-dwarf spectra are complex and notoriously difficult to model, posing challenges to understanding their photospheric properties and compositions in depth. Vanadium (V) is an iron-group element whose abundance supposedly closely tracks that of iron, but has origins that are not completely understood. Our aim is to characterize a series of neutral vanadium atomic absorption lines in the 800-910nm wavelength region of high signal-to-noise, high-resolution, telluric-corrected M-dwarf spectra from the CARMENES survey. Many of these lines are prominent and exhibit a distinctive broad and flat-bottom shape -- a result of hyperfine splitting (HFS). We investigate the potential and implications of these HFS-split lines for abundance analysis of cool stars. With standard spectral synthesis routines, as provided by the spectroscopy software iSpec and the latest atomic data (including HFS) available from the VALD3 database, we model these striking line profiles. We use them to measure V abundances of cool dwarfs. We determine V abundances for 135 early-M dwarfs (M0.0V to M3.5V) in the CARMENES guaranteed time observations sample. They exhibit a [V/Fe]-[Fe/H] trend consistent with that derived from nearby FG dwarfs. The tight (+/-0.1dex) correlation between [V/H] and [Fe/H] suggests the potential application of V as an alternative metallicity indicator in M dwarfs. We also show hints that a neglect to model HFS could partially explain the temperature correlation in V abundance measurements observed in previous studies of samples involving dwarf stars with Teff<=5300K. Our work suggests that HFS can impact certain absorption lines in cool photospheres more severely than in Sun-like ones. Therefore, we advocate that HFS should be carefully treated in abundance studies in stars cooler than ~5000 K. On the other hand, strong HFS split lines in high-resolution spectra present an opportunity for precision chemical analyses of large samples of cool stars. The V-to-Fe trends exhibited by the local M dwarfs continue to challenge theoretical models of V production in the Galaxy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/345/609
- Title:
- Variability of the fine-structure constant
- Short Name:
- J/MNRAS/345/609
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have previously presented evidence for a varying fine-structure constant, {alpha}, in two independent samples of Keck/HIRES quasi-stellar object (QSO) absorption spectra. Here we present a detailed many-multiplet analysis of a third Keck/HIRES sample containing 78 absorption systems. We also re-analyse the previous samples, providing a total of 128 absorption systems over the redshift range 0.2<zabs<3.7.
- ID:
- ivo://CDS.VizieR/J/other/MmSAI/80.833
- Title:
- Variations of the fine-structure constant
- Short Name:
- J/other/MmSAI/80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Keck telescope's High Resolution Spectrograph (HIRES) has previously provided evidence for a smaller fine-structure constant, {alpha}, compared to the current laboratory value, in a sample of 143 quasar absorption systems: {Delta}{alpha}/{alpha}=(-0.57+/-0.11)10^-5^. The analysis was based on a variety of metal-ion transitions which, if alpha varies, experience different relative velocity shifts. This result is yet to be robustly contradicted, or confirmed, by measurements on other telescopes and spectrographs; it remains crucial to do so.
- ID:
- ivo://CDS.VizieR/J/A+A/588/A131
- Title:
- Warm ISM in the Sagittarius A Complex
- Short Name:
- J/A+A/588/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the spatial and spectral distribution of the local standard of rest (LSR) velocity resolved submillimetre emission from the warm (25-90K) gas in the Sgr A Complex, located in the Galactic centre. We present large-scale submillimetre heterodyne observations towards the Sgr A Complex covering ~300-arcmin2. These data were obtained in the frame of the Herschel EXtraGALactic guaranteed time key program (HEXGAL) with the Herschel-HIFI satellite and are complemented with submillimetre observations obtained with the NANTEN2/SMART telescope as part of the NANTEN2/SMART Central Nuclear Zone Survey. The observed species are CO(J=4-3) at 461.0GHz observed with the NANTEN2/SMART telescope, and [CI] 3P1-3P0 at 492.2GHz, [CI] 3P2-3P1 at 809.3GHz, [NII] 3P1-3P0 at 1461.1GHz, and [CII] 2P3/2-2P1/2 at 1900.5GHz observed with the Herschel-HIFI satellite. The observations are presented in a 1km/s spectral resolution and a spatial resolution ranging from 46-arcsec to 28-arcsec. The spectral coverage of the three lower frequency lines is +/-200km/s, while in the two high frequency lines, the upper LSR velocity limit is +94km/s and +145km/s for the [NII] and [CII] lines, respectively. The spatial distribution of the emission in all lines is very widespread. The bulk of the carbon monoxide emission is found towards Galactic latitudes below the Galactic plane, and all the known molecular clouds are identified. Both neutral atomic carbon lines have their brightest emission associated with the +50km/s cloud. Their spatial distribution at this LSR velocity describes a crescent-shape structure, which is probably the result of interaction with the energetic event (one or several supernovae explosions) that gave origin to the non-thermal Sgr A-East source. The [CII] and [NII] emissions have most of their flux associated with the thermal arched-filaments and the H region and bright spots in [CII] emission towards the central nuclear disk (CND) are detected. Warm Gas at very high (|Vlsr|>100km/s) LSR velocities is also detected towards the line of sight to the Sgr A Complex, and it is most probably located outside the region, in the X1 orbits.
- ID:
- ivo://CDS.VizieR/J/AJ/156/295
- Title:
- Warm molecular hydrogen in nearby LIRGs
- Short Name:
- J/AJ/156/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mid-infrared molecular hydrogen (H_2_) emission is a powerful cooling agent in galaxy mergers and in radio galaxies; it is a potential key tracer of gas evolution and energy dissipation associated with mergers, star formation, and accretion onto supermassive black holes. We detect mid-IR H_2_ line emission in at least one rotational transition in 91% of the 214 Luminous Infrared Galaxies (LIRGs) observed with Spitzer as part of the Great Observatories All-sky LIRG Survey. We use H_2_ excitation diagrams to estimate the range of masses and temperatures of warm molecular gas in these galaxies. We find that LIRGs in which the IR emission originates mostly from the Active Galactic Nuclei (AGN) have about 100 K higher H_2_ mass-averaged excitation temperatures than LIRGs in which the IR emission originates mostly from star formation. Between 10% and 15% of LIRGs have H_2_ emission lines that are sufficiently broad to be resolved or partially resolved by the high-resolution modules of Spitzer's Infrared Spectrograph (IRS). Those sources tend to be mergers and contain AGN. This suggests that a significant fraction of the H_2_ line emission is powered by AGN activity through X-rays, cosmic rays, and turbulence. We find a statistically significant correlation between the kinetic energy in the H_2_ gas and the H_2_ to IR luminosity ratio. The sources with the largest warm gas kinetic energies are mergers. We speculate that mergers increase the production of bulk inflows leading to observable broad H_2_ profiles and possibly denser gas.
