- ID:
- ivo://CDS.VizieR/J/A+A/593/A37
- Title:
- Spectral cube toward NGC 6334 I and I(N)
- Short Name:
- J/A+A/593/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HF molecule has been proposed as a sensitive tracer of diffuse interstellar gas, while at higher densities its abundance could be influenced heavily by freeze-out onto dust grains. We investigate the spatial distribution of a collection of absorbing gas clouds, some associated with the dense, massive star-forming core NGC 6334 I, and others with diffuse foreground clouds elsewhere along the line of sight. For the former category, we aim to study the dynamical properties of the clouds in order to assess their potential to feed the accreting protostellar cores. We use far-infrared spectral imaging from the Herschel SPIRE iFTS to construct a map of HF absorption at 243um in a 6'x3.5' region surrounding NGC 6334 I and I(N).
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/135/1239
- Title:
- Spectral distances to DA white dwarfs
- Short Name:
- J/AJ/135/1239
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using recent photometric calibrations, we develop greatly improved distance estimates for DA white dwarfs using multi-band synthetic photometry based on spectroscopic temperatures and gravities. Very good correlations are shown to exist between our spectroscopically based photometric distance estimates and those derived from trigonometric parallaxes. We investigate the uncertainties involved in our distance estimates, as well as discuss the circumstances where such techniques are most likely to fail. We apply our techniques to the large sample of Sloan Digital Sky Survey DA white dwarfs where automated fitting of HI Balmer profiles yields spectrometric temperatures and gravities. We determine simple empirical corrections to these temperatures and gravities with respect to published slit spectroscopy. After applying these T_eff_-logg corrections as well as appropriate interstellar extinction corrections, where necessary, we derive spectroscopically based photometric distances for 7062 DA stars from this sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/41
- Title:
- Spectral & environment properties of z~2 QSO pairs
- Short Name:
- J/ApJ/860/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from our survey of intervening and proximate Lyman limit systems (LLSs) at z~2.0-2.5 using the Wide Field Camera 3 on board the Hubble Space Telescope. The quasars in our sample are projected pairs with proper transverse separations R_{perp}_<=150kpc and line-of- sight velocity separations <~11000km/s. We construct a stacked ultraviolet (rest-frame wavelengths 700-2000{AA}) spectrum of pairs corrected for the intervening Lyman forest and Lyman continuum absorption. The observed spectral composite presents a moderate flux excess for the most prominent broad emission lines, a ~30% decrease in flux at {lambda}=800-900{AA} compared to a stack of brighter quasars not in pairs at similar redshifts, and lower values of the mean free path of the HI ionizing radiation for pairs ({lambda}_mfp_^912^=140.7+/-20.2h_70_^-1^Mpc) compared to single quasars ({lambda}_mfp_^912^=213.8+/-28h_70_^-1^Mpc) at the average redshift z~2.44. From the modeling of LLS absorption in these pairs, we find a higher (~20%) incidence of proximate LLSs with logN_HI_>=17.2 at {delta}v<5000km/s compared to single quasars (~6%). These two rates are different at the 5{sigma} level. Moreover, we find that optically thick absorbers are equally shared between foreground and background quasars. Based on these pieces of evidence, we conclude that there is a moderate excess of gas-absorbing Lyman continuum photons in our closely projected quasar pairs compared to single quasars. We argue that this gas arises mostly within large-scale structures or partially neutral regions inside the dark matter halos where these close pairs reside.
- ID:
- ivo://CDS.VizieR/J/ApJ/682/821
- Title:
- Spectral fits of galaxy clusters in X-ray
- Short Name:
- J/ApJ/682/821
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the band dependence of the inferred X-ray temperature of the intracluster medium (ICM) for 192 well-observed galaxy clusters selected from the Chandra Data Archive. If the hot ICM is nearly isothermal in the projected region of interest, the X-ray temperature inferred from a broadband (0.7-7.0keV) spectrum should be identical to the X-ray temperature inferred from a hard-band (2.0-7.0keV) spectrum. However, if unresolved cool lumps of gas are contributing soft X-ray emission, the temperature of a best-fit single-component thermal model will be cooler for the broadband spectrum than for the hard-band spectrum. Using this difference as a diagnostic, the ratio of best-fitting hard-band and broadband temperatures may indicate the presence of cooler gas even when the X-ray spectrum itself may not have sufficient signal-to-noise ratio (S/N) to resolve multiple temperature components. To test this possible diagnostic, we extract X-ray spectra from core-excised annular regions for each cluster in our archival sample. We compare the X-ray temperatures inferred from single-temperature fits when the energy range of the fit is 0.7-7.0keV (broad) and when the energy range is 2.0/(1+z)-7.0keV (hard). We find that the hard-band temperature is significantly higher, on average, than the broadband temperature. On further exploration, we find this temperature ratio is enhanced preferentially for clusters which are known merging systems. In addition, cool-core clusters tend to have best-fit hard-band temperatures that are in closer agreement with their best-fit broadband temperatures. We show, using simulated spectra, that this diagnostic is sensitive to secondary cool components (T_X_=0.5-3.0keV) with emission measures >=10-30% of the primary hot component.
- ID:
- ivo://CDS.VizieR/J/A+A/423/133
- Title:
- Spectral indexes in HII galaxies
- Short Name:
- J/A+A/423/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse the stellar content of a large number of HII galaxies from the continua and absorption features of their spectra using population synthesis methods, in order to gain information about the star formation histories of these objects. We find that all galaxies of our sample contain an old stellar population (>=1Gyr) that dominates the stellar mass, and in a majority of these we also found evidence for an intermediate-age population >=50Myr apart from the presently bursting, ionizing young generation <=10^7^yr.
- ID:
- ivo://CDS.VizieR/J/AJ/125/2502
- Title:
- Spectral indices of Galactic halo
- Short Name:
- J/AJ/125/2502
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our calibration of spectroscopic measures of luminosity and metallicity for halo giant candidates and give metallicities and distances for our first sample of spectroscopically confirmed giants. These giants have distances ranging from 15 to 83kpc. As surveys reach farther into the Galaxy's halo with K giant samples, identification of giants becomes more difficult. This is because the numbers of foreground halo K dwarfs rise for V magnitudes of 19-20, typical for halo giants at 100kpc. Our photometric survey uses the strength of the Mgb/H feature near 5170{AA} to weed K dwarfs out of the disk and thick disk, but we need spectroscopic measures of the strength of the Ca II K, Ca I {lambda}4227, and Mgb/H features to distinguish between the very metal-poor dwarfs and halo giants. Using a full error analysis of our spectroscopic measures, we show why a signal-to-noise ratio of ~15pixel^-1^ at Ca I {lambda}4227 and ~10 at Ca II K is needed for reliable luminosity discrimination. We use the Ca II K and Mgb features to measure metallicity in our halo giants, with typical errors (random plus systematic) of 0.3dex for [Fe/H] values from -0.8 to -3.0.
- ID:
- ivo://CDS.VizieR/J/AZh/71/200
- Title:
- Spectral Investigation of NGC 7469
- Short Name:
- J/AZh/71/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This investigation is mainly related to hydrogen lines in the spectrum of NGC 7469 from the 1972-1990 data obtained using an image tube on the 2.6-m telescope of the Crimean Astrophysical Observatory. The decomposition of the hydrogen lines into broad and narrow components was performed. Variations in the intensities and broad-component contours were observed. One third of the spectrograms showed a broad, symmetric Ha line, while the others showed asymmetry: the blue wings fall more steeply than the red ones. The degree of asymmetry is variable, but no correlation between it and the brightness of the nucleus was found. This asymmetry becomes weaker when passing to higher members of the Balmer series. The halfwidths of the broad components increase from Ha to H{gamma}. Redshifts of broad components with respect to narrow ones might also be larger for higher members of the Balmer series. Intensities of the broad hydrogen lines follow continuum variations with a delay of about 28 days. The Balmer decrement for broad lines is much flatter than for narrow ones.
- ID:
- ivo://CDS.VizieR/J/AJ/112/241
- Title:
- Spectral irradiance calibration. VI.
- Short Name:
- J/AJ/112/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present three new absolutely calibrated continuous stellar spectra from 3 to 35um, constructed as far as possible from actual observed spectral fragments taken from the Kuiper Airborne Observatory (KAO), and the IRAS Low Resolution Spectrometer (LRS). These stars - alpha1 Cen, alpha TrA, and epsilon Car - augment our previous archive of complete absolutely calibrated spectra for northern K and M giants. All these spectra have a common calibration pedigree. The wavelength coverage is ideal for calibration of many existing and proposed ground-based, airborne, and satellite sensors. KAO and IRAS data in the 15-30 um range suggest that the spectra of cool giants are close to Rayleigh-Jeans slopes. Our observations of alpha1 Cen, absolutely calibrated via our adopted Sirius model, indicate an angular diameter in very good agreement with values in the literature, demonstrating "closure" of the set of spectra within our absolute framework. We compare our observed alpha1 Cen spectrum with a published grid of theoretical models from Kurucz, and adopt a plausible theoretical shape, that fits our spectrum, as a secondary reference spectrum in the southern sky.
- ID:
- ivo://CDS.VizieR/J/AJ/112/2274
- Title:
- Spectral irradiance calibration. VII.
- Short Name:
- J/AJ/112/2274
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present five new absolutely calibrated continuous stellar spectra constructed as far as possible from spectral fragments observed from the ground, the Kuiper Airborne Observatory (KAO), and the IRAS Low Resolution Spectrometer. These stars, alpha Boo, gamma Dra, alpha Cet, gamma Cru, and mu UMa, augment our six, published, absolutely calibrated spectra of K and early-M giants. All spectra have a common calibration pedigree. A revised composite for alpha Boo has been constructed from higher quality spectral fragments than our previously published one. The spectrum of gamma Dra was created in direct response to the needs of instruments aboard the Infrared Space Observatory (ISO); this star's location near the north ecliptic pole renders it highly visible throughout the mission. We compare all our low-resolution composite spectra with Kurucz model atmospheres and find good agreement in shape, with the obvious exception of the SiO fundamental, still lacking in current grids of model atmospheres. The CO fundamental seems slightly too deep in these models, but this could reflect our use of generic models with solar metal abundances rather than models specific to the metallicities of the individual stars. Angular diameters derived from these spectra and models are in excellent agreement with the best observed diameters. The ratio of our adopted Sirius and Vega models is vindicated by spectral observations. We compare IRAS fluxes predicted from our cool stellar spectra with those observed and conclude that, as 12 and 25um, flux densities measured by IRAS should be revised downwards by about 4.1% to 5.7%, respectively, for consistency with our absolute calibration. We have provided extrapolated continuum versions of these spectra to 300um, in direct support of ISO (PHT and LWS instruments). These spectra are consistent with IRAS flux densities at 60 and 100um.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/65.150
- Title:
- Spectral line identification in 3 Pup
- Short Name:
- J/other/AstBu/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical spectra taken in 1997-2008 are used to analyze the spectral peculiarities and velocity field in the atmosphere of the peculiar supergiant 3 Pup.
