Query : 2012A&A...543L...6G

2012A&A...543L...6G - Astronomy and Astrophysics, volume 543, L6-6 (2012/7-1)

Anomaly distribution of quasar magnitudes: a test of lensing by a hypothetic supergiant molecular cloud in the Galactic halo.


Abstract (from CDS):

An anomaly in the distribution of quasar magnitudes based on the Sloan Digital Sky survey, was reported by Longo. The angular size of this quasar anomaly is on the order of ±15° on the sky. A smooth low surface brightness structure detected in γ-rays and at 408MHz, coincides with the sky location and extent of the anomaly, and is close to the northern component of a pair of γ-ray bubbles discovered in the Fermi Gamma-ray Space Telescope survey. Molecular clouds are thought to be illuminated by cosmic rays. Molecular gas in the Galaxy, in the form of cold H2, may be a significant component of dark matter as suggested by Pfenniger et al. I test the hypothesis that the magnitude anomaly in the quasar distribution, is due to lensing by a hypothetical supergiant molecular cloud (SGMC) either in or falling into the Galactic halo. A series of grid lens models are built by assuming that a SGMC is a fractal structure constructed with clumps of 10–3M, 10AU in size, and considering various fractal dimensions. Local amplifications are computed by using the single-plane approximation. A complex network of caustics due to the clumpy structure is present. Our best single plane lens model capable of explaining Longo's effect, at least in sparse regions, requires a mass (1.5-4.1)x1010M within 8.7x8.7x(5-8.6)kpc3 at a lens plane distance of 20kpc, and is constructed from a molecular-cloud building-block of 5x105M within a scale of 30pc expanded by fractal scaling with dimension D=1.8-2 out to 5-8.6kpc for the SGMC. The mass budget depends on the cloud depth and on the fractal dimension. If such a SGMC were found to exist, it may provide at least part of a lensing explanation for the luminous anomaly discovered in quasars and red galaxies.

Abstract Copyright:

Journal keyword(s): gravitational lensing: micro - ISM: clouds - Galaxy: halo - quasars: general - dark matter - gamma rays: ISM

Simbad objects: 3

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Number of rows : 3
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15473 1
2 NAME Fermi Bubbles bub 17 45 -29.0           ~ 306 0
3 NAME Galactic Center gam 17 45 39.60213 -29 00 22.0000           ~ 12320 0

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