- ID:
- ivo://CDS.VizieR/J/MNRAS/463/2653
- Title:
- 8620 DIB equivalent width and extinction
- Short Name:
- J/MNRAS/463/2653
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young stellar cluster Westerlund 1 (Wd 1: l=339.6, b=-0.4) is one of the most massive in the local Universe, but accurate parameters are pending on better determination of its extinction and distance. Based on our photometry and data collected from other sources, we have derived a reddening law for the cluster line-of-sight representative of the Galactic plane (-5{deg}<b<+5{deg}) in the window 0.4-4.8um. The power-law exponent alpha=2.13+/-0.08 is much steeper than those published a decade ago (1.6-1.8) and our index RV=2.50+/-0.04 also differs from them, but in very good agreement with recent works based on deep surveys in the inner Galaxy. As a consequence, the total extinction AKs=0.74+/-0.08 (AV=11.40+/-2.40) is substantially smaller than previous results (0.91-1.13), part of which (AKs=0.63 or AV=9.66) is from the interstellar medium. The extinction in front of the cluster spans a range of AV~8.7 with a gradient increasing from SW to NE across the cluster face, following the same general trend of warm dust distribution. The map of the J-Ks colour index also shows a trend of reddening in this direction. We measured the equivalent width of the diffuse interstellar band at 8620 A (the 'GAIA DIB') for Wd 1 cluster members and derived the relation AKs=0.612EW-0.191EW^2^. This extends the Munari et al. relation, valid for E(B-V)<1, to the non-linear regime (AV>4).
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/550/A108
- Title:
- DIB in VLT-FLAMES Tarantula Survey
- Short Name:
- J/A+A/550/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Tarantula Nebula (a.k.a. 30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud (LMC), seen through gas in the Galactic disc and halo. Diffuse interstellar bands (DIBs) offer a unique probe of the diffuse, cool-warm gas in these regions. The aim is to use DIBs as diagnostics of the local interstellar conditions, whilst at the same time deriving properties of the yet-unknown carriers of these enigmatic spectral features. Spectra of over 800 early-type stars from the Very Large Telescope Flames Tarantula Survey (VFTS) were analysed. Maps were created, separately, for the Galactic and LMC absorption in the DIBs at 4428 and 6614{AA} and - in a smaller region near the central cluster R 136 - neutral sodium (the NaI D doublet); we also measured the DIBs at 5780 and 5797{AA}.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/151
- Title:
- DIB Measurements in 25 atlas sightlines
- Short Name:
- J/ApJ/878/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Aiming for a new and more comprehensive DIB catalog between 4000 and 9000{AA}, we revisited the Atlas Catalog based on the observations of HD 183143 and HD 204827. Twenty-five medium to highly reddened sight lines were selected, sampling a variety of spectral types of the background star and the interstellar environments. The median signal-to-noise ratio (S/N) of these spectra is ~1300 around 6400{AA}. Compared to the Atlas Catalog, 22 new DIBs were found, and the boundaries of 27 (sets of) DIBs were adjusted, resulting in an updated catalog containing 559 DIBs that we refer to as the Apache Point Observatory Catalog of Optical Diffuse Interstellar Bands. Measurements were then made based on this catalog. We found our survey most sensitive between 5500 and 7000{AA}, due largely to the local S/N of the spectra, the relative absence of interfering stellar lines, and the weakness of telluric residuals. For our data sample, the number of DIBs detected in a given sight line is mostly dependent on E_B-V_ and less on the spectral type of the background star. Some dependence on the molecular fraction f_H2_ is observed, but it is less well determined owing to the limited size of the data sample. The variations of the wavelengths of each DIB in different sight lines are generally larger than those of the known interstellar lines CH^+^, CH, and KI. Those variations could be due to the inherent error in the measurement, or to differences in the velocity components among sight lines.
- ID:
- ivo://CDS.VizieR/J/MNRAS/461/839
- Title:
- DIB 661.3nm in Cepheid spectra
- Short Name:
- J/MNRAS/461/839
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated the diffuse interstellar band (DIB) at 661.3nm seen in the spectra of Cepheid stars. After removal of the blending lines of ionized yttrium and neutral iron, we determined the equivalent widths (EWs) of the DIB and used these values to investigate the E(B-V)-DIB EW relation. The relation found from Cepheids matches that found in B stars. This relation can help to find the reddening for newly discovered Cepheids without extensive photometric data, and thus determine their distances. The relation between E(B - V) and the DIB EW does not yield precise reddening values. It is not a substitute for better photometric or spectroscopic methods. At best, it is indicative, but it provides some information that may not be otherwise available. Defining R*=E(B-V)/DIB EW, which we consider to be the analogue of R=E(B-V)/A_V_, we investigated the Galactic longitudinal dependence of R* assuming that the DIB EW value is representative of the interstellar absorption A$_v$. We found that there is an apparent increase of the R* value that corresponds to the abnormal absorption seen towards Cygnus constellation. Finally, we constructed a 2D map of the DIB EW distribution in the Galactic disc basing on our rather limited sample of 253 spectra of 176 Cepheids.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A52
- Title:
- DIB properties in lines of sight to M17
- Short Name:
- J/A+A/620/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Diffuse interstellar bands (DIBs) are broad absorption features measured in sightlines probing the diffuse interstellar medium. Although large carbon-bearing molecules have been proposed as the carriers producing DIBs, their identity remains unknown. DIBs make an important contribution to the extinction curve; the sightline. to the young massive star-forming region M17 shows anomalous extinction in the sense that the total-to-selective extinction parameter (R_V_) differs significantly from the average Galactic value and may reach values R_V_>4. Anomalous DIBs have been reported in the sightline towards Herschel 36 (R_V_=5.5), in the massive star-forming region M8. Higher values of R_V_ have been associated with a relatively higher fraction of large dust grains in the line of sight. Given the high R_V_ values, we investigate whether the DIBs in sightlines towards young OB stars in M17 show a peculiar behaviour. We measure the properties of the most prominent DIBs in M17 and study these as a function of E(B-V) and R_V_. We also analyse the gaseous and dust components contributing to the interstellar extinction. The DIB strengths in M17 concur with the observed relations between DIB equivalent width and reddening E(B-V) in Galactic sightlines. For several DIBs we discover a linear relation between the normalised DIB strength EW/A_V_ and R_V_^-1^. These trends suggest two groups of DIBs: (i) a group of ten moderately strong DIBs that show a sensitivity to changes in R_V_ that is modest and proportional to DIB strength, and (ii) a group of four very strong DIBs that react sensitively and to a similar degree to changes in R_V_, but in a way that does not appear to depend on DIB strength. DIB behaviour as a function of reddening is not peculiar in sightlines to M17. Also, we do not detect anomalous DIB profiles like those seen in Herschel 36. DIBs are stronger, per unit visual extinction, in sightlines characterised by a lower value of R_V_, i.e. those sightlines that contain a relatively large fraction of small dust particles. New relations between extinction normalised DIB strengths, EW/A_V_, and R_V_ support the idea that DIB carriers and interstellar dust are intimately connected. Furthermore, given the distinct behaviour of two groups of DIBs, different types of carriers do not necessarily relate to the dust grains in a similar way.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A62
- Title:
- DIBs from Baade's window bulge clump giants
- Short Name:
- J/A+A/550/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Interstellar (IS) absorption lines or diffuse bands are usually extracted from early-type star spectra because they are characterized by smooth continua. However, this introduces a strong limitation on the number of available targets, and reduces potential studies of the IS matter and the use of absorptions for cloud mapping. We have developed a new and automated fitting method appropriate to interstellar (IS) absorptions in the spectra of cool stars that possess stellar atmospheric parameters. We applied this method to the extraction of three diffuse interstellar bands (DIBs) in high resolution VLT FLAMES/GIRAFFE spectra of red-clump stars from the bulge. By combining all stellar synthetic spectra, HITRAN-LBLRTM atmospheric transmission spectra and diffuse band empirical absorption profiles, we determined the 6196.0, 6204.5, and 6283.8{AA} DIB strength toward the 219 target stars and discuss the sources of uncertainties. To test the sensitivity of the DIB extraction, we compared all three results and compared the DIB equivalent widths (EWs) with the reddening derived from an independent extinction map based on OGLE photometric data. We also derived the three independent color excess estimates based on the DIB strengths and average linear correlation coefficients previously established in the solar neighborhood and compared with the OGLE photometric results.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A129
- Title:
- DIBs in APOGEE telluric standard star spectra
- Short Name:
- J/A+A/600/A129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Information on the existence and properties of diffuse interstellar bands (DIBs) outside the optical domain is still limited. Additional infra-red (IR) measurements and IR-optical correlative studies are needed to constrain DIB carriers and locate various absorbers in 3D maps of the interstellar matter. We extended our study of H-band DIBs in Apache Point Observatory Galactic Evolution Experiment (APOGEE) Telluric Standard Star (TSS) spectra. We used the strong {lambda}15273 band to select the most and least absorbed targets. We used individual spectra of the former subsample to extract weaker DIBs, and we searched the two stacked series for differences that could indicate additional bands. High-resolution NARVAL and SOPHIE optical spectra for a subsample of 55 TSS targets were additionally recorded for NIR/optical correlative studies. From the TSS spectra we extract a catalog of measurements of the poorly studied {lambda}{lambda}15617, 15653, and 15673 DIBs in ~300 sightlines, we obtain a first accurate determination of their rest wavelength and constrained their intrinsic width and shape. In addition, we studied the relationship between these weak bands and the strong {lambda}15273 DIB.We provide a first or second confirmation of several other weak DIBs that have been proposed based on different instruments, and we add new constraints on their widths and locations. We finally propose two new DIB candidates. We compared the strength of the {lambda}15273 15273 absorptions with their optical counterparts {lambda}{lambda}5780, 5797, 6196, 6283, and 6614. Using the 5797-5780 ratio as a tracer of shielding against the radiation field, we showed that the {lambda}15273 DIB carrier is significantly more abundant in unshielded ({sigma}-type) clouds, and it responds even more strongly than the {lambda}5780 band carrier to the local ionizing field.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/4013
- Title:
- DIBs in Magellanic Clouds and Milky Way
- Short Name:
- J/MNRAS/454/4013
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Diffuse interstellar bands (DIBs) trace warm neutral and weakly ionized diffuse interstellar medium (ISM). Here we present a dedicated, high signal-to-noise spectroscopic survey of two of the strongest DIBs, at 5780 and 5797{AA}, in optical spectra of 666 early-type stars in the Small and Large Magellanic Clouds, along with measurements of the atomic NaI D and CaII K lines. The resulting maps show for the first time the distribution of DIB carriers across large swathes of galaxies, as well as the foreground Milky Way ISM. We confirm the association of the 5797{AA} DIB with neutral gas, and the 5780{AA} DIB with more translucent gas, generally tracing the star-forming regions within the Magellanic Clouds. Likewise, the NaI D line traces the denser ISM whereas the CaII K line traces the more diffuse, warmer gas. The CaII K line has an additional component at ~200-220km/s seen towards both Magellanic Clouds; this may be associated with a pan-Magellanic halo. Both the atomic lines and DIBs show sub-pc-scale structure in the Galactic foreground absorption; the 5780 and 5797{AA} DIBs show very little correlation on these small scales, as do the CaII K and NaI D lines. This suggests that good correlations between the 5780 and 5797{AA} DIBs, or between CaII K and NaI D, arise from the superposition of multiple interstellar structures. Similarity in behaviour between DIBs and NaI in the Small Magellanic Cloud (SMC), Large Magellanic Cloud (LMC) and Milky Way suggests the abundance of DIB carriers scales in proportion to metallicity.
- ID:
- ivo://CDS.VizieR/J/ApJS/225/19
- Title:
- DIBs measurements from SDSS-III APOGEE spectra
- Short Name:
- J/ApJS/225/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High resolution stellar spectroscopic surveys provide massive amounts of diffuse interstellar bands (DIBs) measurements. Data can be used to study the distribution of the DIB carriers and those environmental conditions that favor their formation. In parallel, recent studies have also proved that DIBs extracted from stellar spectra constitute new tools for building the 3D structure of the Galactic interstellar medium (ISM). The amount of details on the structure depends directly on the quantity of available lines of sight. Therefore there is a need to construct databases of high-quality DIB measurements as large as possible. We aim at providing the community with a catalog of high-quality measurements of the 1.5273{mu}m DIB toward a large fraction of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) hot stars observed to correct for the telluric absorption and not used for ISM studies so far. This catalog would complement the extensive database recently extracted from the APOGEE observations and used for 3D ISM mapping. We devised a method to fit the stellar continuum of the hot calibration stars and extracted the DIB from the normalized spectrum. Severe selection criteria based on the absorption characteristics are applied to the results. In particular limiting constraints on the DIB widths and Doppler shifts are deduced from the HI 21cm measurements, following a new technique of decomposition of the emission spectra. From ~16000 available hot telluric spectra we have extracted ~6700 DIB measurements and their associated uncertainties. The statistical properties of the extracted absorptions are examined and our selection criteria are shown to provide a robust dataset. The resulting catalog contains the DIB total equivalent widths, central wavelengths and widths. We briefly illustrate its potential use for the stellar and interstellar communities.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A69
- Title:
- Di-deuterated methanol (CHD2OH) line list
- Short Name:
- J/A+A/659/A69
- Date:
- 14 Mar 2022 07:43:58
- Publisher:
- CDS
- Description:
- Di-deuterated molecules are observed in the earliest stages of star formation at abundances of a few percent relative to their nondeuterated isotopologs, which is unexpected considering the scarcity of deuterium in the interstellar medium. With sensitive observations leading to the detection of a steadily increasing number of di-deuterated species, it is becoming possible to explore successive deuteration chains. The accurate quantification of the column density of di-deuterated methanol is a key piece of the puzzle that is missing in the otherwise thoroughly constrained family of D-bearing methanol in the deeply embedded low-mass protostellar system and astrochemical template source IRAS 16293-2422. A spectroscopic dataset for astrophysical purposes was built for CHD2OH and made publicly available to facilitate the accurate characterization of this species in astrochemical surveys. The newly computed line list and partition function were used to search for CHD_2_OH toward IRAS 16293-2422 A and B in data from the Atacama Large Millimeter/submillimeter Array (ALMA) Protostellar Interferometric Line Survey (PILS). Only nonblended, optically thin lines of CHD_2_OH were used for the synthetic spectral fitting. The constructed spectroscopic database contains line frequencies and strengths for 7417 transitions in the 0-500GHz frequency range. ALMA-PILS observations in the 329-363GHz range were used to identify 105 unique, nonblended, optically thin line frequencies of CHD2OH for synthetic spectral fitting. The derived excitation temperatures and column densities yield high D/H ratios of CHD2OH in IRAS 16293-2422 A and B of 7.5+/-1.1% and 7.7+/-1.2%, respectively. Deuteration in IRAS 16293-2422 is not higher than in other low-mass star-forming regions (L483, SVS13-A, NGC 1333-IRAS2A, -IRAS4A, and -IRAS4B). Di-deuterated molecules consistently have higher D/H ratios than their mono-deuterated counterparts in all low-mass protostars, which may be a natural consequence of H-D substitution reactions as seen in laboratory experiments. The Solar System's natal cloud, as traced by comet 67P/Churyumov-Gerasimenko, may have had a lower initial abundance of D, been warmer than the cloud of IRAS 16293-2422, or been partially reprocessed. In combination with accurate spectroscopy, a careful spectral analysis, and the consideration of the underlying assumptions, successive deuteration is a robust window on the physicochemical provenance of star-forming systems.