A high sensitivity HI survey of the sky at $\mathsf{\delta \le -25 \degr}$

Bajaja, E.; Arnal, E. M.; Larrarte, J. J.; Morras, R.; Pöppel, W. G. L.; Kalberla, P. M. W.

doi:10.1051/0004-6361:20041863

Cited by 116 publications

(125 citation statements)

References 9 publications

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“…We use the 21cm Leiden/Argentine/Bonn (LAB) data Hartmann & Burton, 1997;Bajaja et al, 2005;Arnal et al, 2000) to conduct a quantitative study of the warp and spiral structure. We used the Hanning smoothed data, which have a velocity resolution of 1.9 km s −1 , and restricted our sample to |b| ≤ 30 • .…”

Section: Methodsmentioning

confidence: 99%

The Warp and Spiral Arms of the Milky Way

Levine

Blitz

Heiles

et al. 2008

Mapping the Galaxy and Nearby Galaxies

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We examine the outer Galactic HI disk for deviations from the b = 0 • plane by constructing maps of disk surface density, mean height, and thickness. We find that the Galactic warp is well described by a vertical offset plus two Fourier modes of frequency 1 and 2, all of which grow with Galactocentric radius. A perturbation theory calculation demonstrates that the tidal influence of the Magellanic Clouds creates distortions in the dark matter halo, which combine to produce disk warp amplitudes comparable to the observations. We also construct a detailed map of the perturbed surface density of HI in the outer disk demonstrating that the Galaxy is a non-axisymmetric multi-armed spiral. Overdensities in the surface density are coincident with regions of reduced gas thickness. MethodWe use the 21cm Leiden/Argentine/Bonn (LAB) data Hartmann & Burton, 1997;Bajaja et al., 2005;Arnal et al., 2000) to conduct a quantitative study of the warp and spiral structure. We used the Hanning smoothed data, which have a velocity resolution of 1.9 km s −1 , and restricted our sample to |b| ≤ 30 • . We apply a median filter to the data to remove angularly small, bright features that are clearly not associated with the disk. To create a map of the Galaxy from the data, we must assume a rotation structure for the disk. Using a flat rotation curve with circular orbits results in a large asymmetry between the surface densities at Galactic longitudes on either side of ℓ = 0 • and ℓ = 180 • . To eliminate this discontinuity, we assume that the gas is traveling on elliptical streamlines configured such that the surface densities are smooth across the ℓ = 180 • line (see Levine et al. (2006a)). We exclude all points that lie within 345Points in these two wedges have velocities along the line of sight that are too small with respect to their random velocities to establish reliable distances.

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Section: Methodsmentioning

confidence: 99%

The Warp and Spiral Arms of the Milky Way

Levine

Blitz

Heiles

et al. 2008

Mapping the Galaxy and Nearby Galaxies

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“…• 5 were observed with the 30-m telescope of the Instituto Argentino de Radioastronomía (IAR) by Bajaja et al (2005). Figure 11 displays Fig.…”

Section: Comparison Between Gass and Labmentioning

confidence: 99%

GASS: The Parkes Galactic All-Sky Survey

Kalberla

Haud

2015

A&A

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139

148

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Context. The Galactic All-Sky Survey (GASS) is a survey of Galactic atomic hydrogen (H i) emission in the southern sky observed with the Parkes 64-m Radio Telescope. The first data release (GASS I) concerned survey goals and observing techniques, the second release (GASS II) focused on stray radiation and instrumental corrections. Aims. We seek to remove the remaining instrumental effects and present a third data release. Methods. We use the HEALPix tessellation concept to grid the data on the sphere. Individual telescope records are compared with averages on the nearest grid position for significant deviations. All averages are also decomposed into Gaussian components with the aim of segregating unacceptable solutions. Improved priors are used for an iterative baseline fitting and cleaning. In the last step we generate 3D FITS data cubes and examine them for remaining problems. Results. We have removed weak, but systematic baseline offsets with an improved baseline fitting algorithm. We have unraveled correlator failures that cause time dependent oscillations; errors cause stripes in the scanning direction. The remaining problems from radio frequency interference (RFI) are spotted. Classifying the severeness of instrumental errors for each individual telescope record (dump) allows us to exclude bad data from averages. We derive parameters that allow us to discard dumps without compromising the noise of the resulting data products too much. All steps are reiterated several times: in each case, we check the Gaussian parameters for remaining problems and inspect 3D FITS data cubes visually. We find that in total ∼1.5% of the telescope dumps need to be discarded in addition to ∼0.5% of the spectral channels that were excluded in GASS II. Conclusions. The new data release (GASS III) facilitates data products with improved quality. A new web interface, compatible with the previous version, is available for download of GASS III FITS cubes and spectra.

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“…The 21 cm maps (Kalberla et al 2005) are the combined Leiden/Dwingeloo (Hartmann & Burton 1997) and Instituto Argentino de Radioastronomía (Bajaja et al 2005) surveys detecting H i over a velocity range of −450 km s −1 to +400 km s −1 at 1.3 km s −1 resolution with very high equivalent main beam efficiency ( 0.99).…”

Section: Sample Selection Data Reduction and Analysismentioning

confidence: 99%

The Galactic dust-to-metals ratio and metallicity using gamma-ray bursts

Watson

2011

A&A

114

108

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The metallicity and dust-to-metals ratio of the Galaxy are fundamental parameters in understanding the interstellar medium (ISM). Currently, there is still some uncertainty surrounding these parameters. In this paper, the dust-to-metals ratio in the Galaxy is determined using the photoelectric absorption of the soft X-ray afterglows of a large sample of several hundred gamma-ray bursts (GRBs) to determine the metal column density in combination with Galactic dust maps to determine the line-of-sight dust extinction through the Galaxy in the direction of the GRB. GRB afterglows often have large extragalactic soft X-ray absorptions and therefore the GRB sample's upper-bound will define the Galactic dust-to-metals relation. Using a two-dimensional two-sample Kolmogorov-Smirnoff test, we determine this upper-bound and so derive the dust-to-metals ratio of the Galaxy. We find N H = 2.2 +0.3 −0.4 × 10 21 cm −2 A V asassuming solar, Anders & Grevesse (1989, Geochim. Cosmochim. Acta, 53, 197), metallicity. This result is consistent with previous findings using bright X-ray sources in the Galaxy. Using the same technique but substituting the H i maps from the Leiden-ArgentineBonn survey for the dust maps, allows us to place a limit on the metallicity in the Galaxy. We find a metallicity consistent with the Anders & Grevesse (1989) solar values often used in X-ray fitting. Based on this and previous studies, we suggest that the metallicity of a typical ISM sightline through the Galaxy is ∼0.25 dex higher than the current best estimate of the solar metallicity. We further show that the dust-to-gas ratio seems to be correlated with the total gas column density, and that this may be due to the metallicity gradient observed toward the Galactic centre. Based on the non-constant nature of the dust-to-gas ratio, we propose that the dust column density, at N H = 2.2 × 10 21 cm −2 A V , represents a better proxy for the soft X-ray absorption column density than H i maps.

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A high sensitivity HI survey of the sky at $\mathsf{\delta \le -25 \degr}$

Cited by 116 publications

References 9 publications

The Warp and Spiral Arms of the Milky Way

The Warp and Spiral Arms of the Milky Way

GASS: The Parkes Galactic All-Sky Survey

The Galactic dust-to-metals ratio and metallicity using gamma-ray bursts

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