J/PAZh/38/15 Total-to-selective extinction ratio within 700pc (Gontcharov, 2012)
Variations of the interstellar extinction law within the nearest kiloparsec.
Gontcharov G.A.
<Pis'ma Astron. Zh. 38, 15 (2012)>
=2012PAZh...38...15G 2012PAZh...38...15G (SIMBAD/NED BibCode)
=2012AstL...38...12G 2012AstL...38...12G
ADC_Keywords: Extinction; Interstellar medium; Milky Way; Reddening
Keywords: extinction - interstellar medium - stars: early-type -
stars: late-type
Abstract:
Multicolor photometry from the Tycho-2 and 2MASS catalogues for 11990
OB (2008AstL...34....7G 2008AstL...34....7G; 2012AstL...38..694G 2012AstL...38..694G) and 30671 K-type red
giant branch stars (2011AstL...37..707G 2011AstL...37..707G) is used to detect systematic
large-scale variations of the interstellar extinction law within the
nearest kiloparsec. The characteristic of the extinction law, the
total-to-selective extinction ratio Rv, which also characterizes the
size and other properties of interstellar dust grains, has been
calculated for various regions of space by the extinction law
extrapolation method. The results for the two classes of stars agree:
the standard deviation of the "red giants minus OB" Rv differences
within 500pc of the Sun is 0.2. The detected Rv variations between
2.2 and 4.4 not only manifest themselves in individual clouds but also
span the entire space near the Sun, following Galactic structures. In
the Local Bubble within about 100 pc of the Sun, Rv has a minimum. In
the inner part of the Gould Belt and at high Galactic latitudes, at a
distance of about 150 pc from the Sun, Rv reaches a maximum and then
decreases to its minimum in the outer part of the Belt and other
directions at a distance of about 500 pc from the Sun, returning to
its mean values far from the Sun. The detected maximum of Rv at high
Galactic latitudes is important when allowance is made for the
interstellar extinction toward extragalactic objects. In addition, a
monotonic increase in Rv by 0.3 per kpc toward the Galactic center has
been found near the Galactic equator. It is consistent with the result
obtained by Zasowski et al. (2009ApJ...707..510Z 2009ApJ...707..510Z) for much of the
Galaxy. Ignoring the Rv variations and traditionally using a single
value for the entire space must lead to systematic errors in the
calculated distances reaching 10%.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
mapxyzr.dat 19 1540 Rv tabulated as a function of X, Y, Z coordinates
--------------------------------------------------------------------------------
See also:
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
I/311 : Hipparcos, the new Reduction of the Raw data (van Leeuwen 2007)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/PAZh/36/615 : 3D reddening map for stars from 2MASS phot. (Gontcharov, 2010)
J/PAZh/38/776 : Complete sample of OB stars within 350pc (Gontcharov, 2012)
J/PAZh/38/108 : 3D interstellar extinction map within nearest kpc
(Gontcharov, 2012)
Byte-by-byte Description of file: mapxyzr.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 pc X [-650,650] X rectangular galactic coordinate (1)
6- 9 I4 pc Y [-650,650] Y rectangular galactic coordinate (1)
11- 14 I4 pc Z [-600,600] Z rectangular galactic coordinate (1)
16- 19 F4.2 --- Rv Total-to-selective extinction ratio (2)
--------------------------------------------------------------------------------
Note (1): The coordinates are taken from Gontcharov, 2008AstL...34....7G 2008AstL...34....7G and
2011AstL...37..707G 2011AstL...37..707G.
Note (2): The Rv are calculated in this paper for nearly a sphere of radius
700 pc around the Sun and presented as the values for the cubes of
100x100x100 pc. It should be interpolated between the centres of the cubes.
--------------------------------------------------------------------------------
Acknowledgements:
George Gontcharov, georgegontcharov(at)yahoo.com
(End) George Gontcharov [Pulkovo Obs.], Patricia Vannier [CDS] 14-Jan-2016