Science Letter
June 22, 2010
ASTRONOMY;
Studies from L.A. Sargsyan and co-researchers yield new data on astronomy
“We present samples of starburst galaxies that represent the extremes
discovered with infrared and ultraviolet observations, including 25
Markarian galaxies, 23 ultraviolet-luminous galaxies discovered with
GALEX, and the 50 starburst galaxies having the largest
infrared/ultraviolet ratios. These sources have z< 0.5 and cover a
luminosity range of similar to 10(4)," scientists in Armenia report
(see also Astronomy).
"Comparisons between infrared luminosities determined with the 7.7 mu
m polycyclic aromatic hydrocarbon feature and ultraviolet luminosities
from the stellar continuum at 153 nm are used to determine obscuration
in starbursts and dependence of this obscuration on infrared or
ultraviolet luminosity. A strong selection effect arises for the
ultraviolet- selected samples: the brightest sources appear bright
because they have the least obscuration. Obscuration correction for
the ultraviolet- selected Markarian+GALEX sample has the form
log[UV(intrinsic)/UV(observed)] = 0.07(+/-0.04)M(UV) + 2.09 +/- 0.69
but for the full infrared-selected Spitzer sample is
log[UV(intrinsic)/UV(observed)] = 0.17(+/-0.02)M(UV) + 4.55 +/- 0.4.
The relation of total bolometric luminosity L-ir to M(UV) is also
determined for infrared-selected and ultraviolet-selected samples. For
ultraviolet-selected galaxies, log (Lir) = -(0.33 +/- 0.04) M(UV) +
4.52 +/- 0.69. For the full infrared-selected sample, log L-ir
-(0.23 +/- 0.02) M(UV) + 6.99 +/- 0.41, all for L-ir in L-circle dot
and M(UV) the AB magnitude at rest frame 153 nm," wrote L.A. Sargsyan
and colleagues.
The researchers concluded: "These results imply that obscuration
corrections by factors of 2-3 determined from reddening of the
ultraviolet continuum for Lyman break galaxies with z> 2 are
insufficient, and should be at least a factor of 10 for M(UV) similar
to -17, with decreasing correction for more luminous sources.”
Sargsyan and colleagues published their study in Astrophysical Journal
(Comparing Ultraviolet-and Infrared-selected Starburst Galaxies In
Dust Obscuration And Luminosity. Astrophysical Journal,
2010;715(2):986-1005).
For additional information, contact L.A. Sargsyan, Byurakan
Astrophysics Observ, Byurakan 378433, Aragatzotn, Armenia.
The publisher’s contact information for the Astrophysical Journal is:
IOP Publishing Ltd., Dirac House, Temple Back, Bristol BS1 6BE,
England.
From: A. Papazian