GASS: the Parkes Galactic all-sky survey

Kalberla, P. M. W.; McClure-Griffiths, N. M.; Pisano, D. J.; Calabretta, M. R.; Ford, H. Alyson; Lockman, Felix J.; Staveley‐Smith, L.; Kerp, J.; Winkel, B.; Murphy, Tara; Newton‐McGee, K.

doi:10.1051/0004-6361/200913979

Cited by 201 publications

(231 citation statements)

References 24 publications

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“…For the remaining lines of sight we make use of the new large-area H i 21-cm surveys GASS (Galactic All-Sky survey, McClure-Griffiths et al 2009;Kalberla et al 2010) and EBHIS (Effelsberg-Bonn HI survey, Winkel et al 2010;Kerp et al 2011). Compared to BB08, this leads to a substantially increased number of H i spectra available for follow-up analyses.…”

Section: Introductionmentioning

confidence: 99%

An absorption-selected survey of neutral gas in the Milky Way halo

Bekhti

Winkel

Richter

et al. 2012

A&A

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Aims. We aim at analysing systematically the distribution and physical properties of neutral and mildly ionised gas in the Milky Way halo, based on a large absorption-selected data set. Methods.Multi-wavelength studies were performed combining optical absorption line data of Ca ii and Na i with follow-up H i 21-cm emission line observations along 408 sight lines towards low-and high-redshift QSOs. We made use of archival optical spectra obtained with UVES/VLT. H i data were extracted from the Effelsberg-Bonn H i survey and the Galactic All-Sky survey.For selected sight lines we obtained deeper follow-up observations using the Effelsberg 100-m telescope.Results. Ca ii (Na i) halo absorbers at intermediate and high radial velocities are present in 40-55% (20-35%) of the sightlines, depending on the column density threshold chosen. Many halo absorbers show multi-component absorption lines, indicating the presence of sub-structure. In 65% of the cases, absorption is associated with H i 21-cm emission. The Ca ii (Na i) column density distribution function follows a power-law with a slope of β ≈ −2.2 (−1.4). Conclusions. Our absorption-selected survey confirms our previous results that the Milky Way halo is filled with a large number of neutral gas structures whose high column density tail represents the population of common H i high-and intermediate-velocity clouds seen in 21-cm observations. We find that Na i/Ca ii column density ratios in the halo absorbers are typically smaller than those in the Milky Way disc, in the gas in the Magellanic Clouds, and in damped Lyman α systems. The small ratios (prominent in particular in high-velocity components) indicate a lower level of Ca depletion onto dust grains in Milky Way halo absorbers compared to gas in discs and inner regions of galaxies.

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Section: Introductionmentioning

confidence: 99%

An absorption-selected survey of neutral gas in the Milky Way halo

Bekhti

Winkel

Richter

et al. 2012

A&A

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“…Specifically, we impose limits on the expected velocities for the DIBs, based on the direction of the sky and on the results for H i (Brand & Blitz 1993;Kalberla et al 2010). Each UVES spectrum was fitted twice.…”

Section: Dib Extraction Using the New Line Listmentioning

confidence: 99%

“…However, this is not necessarily true. For example, in the direction of NGC 6705, H i observations show at least the existence of two clouds at very different velocities (Kalberla et al 2010). The simplicity of a fit using only one component coupled with differences in the physical conditions between these clouds might also explain the velocities differences observed between the different DIBs.…”

Section: Dib Extraction Using the New Line Listmentioning

confidence: 99%

Measuring diffuse interstellar bands with cool stars

Monreal-Ibero

Lallement

2017

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Context. Diffuse Stellar Bands (DIBs) are ubiquitous in stellar spectra. Traditionally, they have been studied through their extraction from hot (early-type) stars, because of their smooth continuum. In an era where there are several going-on or planned massive Galactic surveys using multi-object spectrographs, cool (late-type) stars constitute an appealing set of targets. However, from the technical point of view, the extraction of DIBs in their spectra is more challenging due to the complexity of the continuum. Aims. In this contribution we will provide the community with an improved set of stellar lines in the spectral regions associated to the strong DIBs at λ6196.0, λ6269.8, λ6283.8, and λ6379.3. These lines will allow for the creation of better stellar synthetic spectra, reproducing the background emission and a more accurate extraction of the magnitudes associated with a given DIB (e.g. equivalent width, radial velocity). Methods. The Sun and Arcturus were used as representative examples of dwarf and giant stars, respectively. A high quality spectrum for each of them was modeled using TURBOSPECTRUM and the VALD stellar line list. The oscillator strength log(g f ) and/or wavelength of specific lines were modified to create synthetic spectra where the residuals in both the Sun and Arcturus were minimized. Results. The TURBOSPECTRUM synthetic spectra based on the improved line lists reproduce the observed spectra for the Sun and Arcturus in the mentioned spectral ranges with greater accuracy. Residuals between the synthetic and observed spectra are always ∼ < 10%, much better than with previously existing options. The new line list has been tested with some characteristic spectra, from a variety of stars, including both giant and dwarf stars, and under different degrees of extinction. As it happened with the Sun and Arcturus residuals in the fits used to extract the DIB information are smaller when using synthetic spectra made with the updated line lists. Tables with the updated parameters are provided to the community.

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“…There was also a dependence on beam, but only between the central beam (Beam 1), beams in the inner ring as a set (Beams 2-7), and those in the outer ring (Beams 8-13). Plausibly, the dependence on ζ and beam may result from the asymmetry of the inner and outer beams as illustrated by Kalberla et al (2010). The general form of the dependence is dT sys = ∂T sys ∂η dη + ∂T sys ∂ζ dζ .…”

Section: Ghz Radio Continuum Map Of δ < +25 •mentioning

confidence: 99%