- ID:
- ivo://CDS.VizieR/J/A+A/591/A20
- Title:
- DIB and NaD spectra of 3 nearby stars
- Short Name:
- J/A+A/591/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Diffuse interstellar absorption bands (DIBs) of largely unknown chemical origin are regularly observed primarily in distant early-type stars. More recently, detections in nearby late-type stars have also been claimed. These stars' spectra are dominated by stellar absorption lines. Specifically, strong interstellar atomic and DIB absorption has been reported in tau Boo. We test these claims by studying the strength of interstellar absorption in high-resolution TIGRE spectra of the nearby stars tau Boo, HD 33608, and alpha CrB. We focus our analysis on a strong DIB located at 5780.61{AA} and on the absorption of interstellar Na. First, we carry out a differential analysis by comparing the spectra of the highly similar F-stars, tau Boo and HD 33608, whose light, however, samples different lines of sight. To obtain absolute values for the DIB absorption, we compare the observed spectra of tau Boo, HD 33608, and alpha CrB to PHOENIX models and carry out basic spectral modeling based on Voigt line profiles.
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- 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/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/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/423/579
- Title:
- Diffuse emissions in Carina nebula
- Short Name:
- J/A+A/423/579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of mapping observations with ISO of [OI]63{mu}m, 145{mu}m, [NII]122{mu}m, [CII]158{mu}m, [SiII]35{mu}m, and H_2_9.66{mu}m line emissions for the Carina nebula, an active star-forming region in the Galactic plane. The observations were made for the central 40'x20' area of the nebula, including the optically bright HII region and molecular cloud lying in front of the ionized gas. Around the center of the observed area is the interface between the HII region and the molecular cloud which creates a typical photodissociation region (PDR).
- ID:
- ivo://CDS.VizieR/J/ApJ/733/91
- Title:
- Diffuse interstellar band equivalent widths
- Short Name:
- J/ApJ/733/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The diffuse interstellar bands (DIBs) are ubiquitous absorption spectral features arising from the tenuous material in the space between stars -the interstellar medium (ISM). Since their first detection nearly nine decades ago, over 400 DIBs have been observed in the visible and near-infrared wavelength range in both the Milky Way and external galaxies, both nearby and distant. However, the identity of the species responsible for these bands remains as one of the most enigmatic mysteries in astrophysics. An equally mysterious interstellar spectral signature is the 2175{AA} extinction bump, the strongest absorption feature observed in the ISM. Its carrier also remains unclear since its first detection 46 years ago. Polycyclic aromatic hydrocarbon (PAH) molecules have long been proposed as a candidate for DIBs as their electronic transitions occur in the wavelength range where DIBs are often found. In recent years, the 2175{AA} extinction bump is also often attributed to the {pi}-{pi}* transition in PAHs. If PAHs are indeed responsible for both the 2175{AA} extinction feature and DIBs, their strengths may correlate. We perform an extensive literature search for lines of sight for which both the 2175{AA} extinction feature and DIBs have been measured. Unfortunately, we found no correlation between the strength of the 2175{AA} feature and the equivalent widths of the strongest DIBs. A possible explanation might be that DIBs are produced by small free gas-phase PAH molecules and ions, while the 2175{AA} bump is mainly from large PAHs or PAH clusters in condensed phase so that there is no tight correlation between DIBs and the 2175{AA} bump.
- ID:
- ivo://CDS.VizieR/II/149
- Title:
- Diffuse Interstellar Band Measurements
- Short Name:
- II/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains diffuse band data collected from an exhaustive search of the literature and reduced to a common measurement system. The authors have adopted Herbig (1975ApJ...196..129H) as a standard data set for DIB measurements.
