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Combined constraints on intergalactic dust from quasar colours and the soft x ray background
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
2012 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 426, no 4, 3360-3368 p.Article in journal (Refereed) Published
Abstract [en]

Unless properly corrected for, the existence of intergalactic dust will introduce a redshift-dependent magnitude offset to standard candle sources. This would lead to overestimated luminosity distances compared to a dust-free universe and bias the cosmological parameter estimation as derived from, e.g., Type Ia supernova observations. In this paper, we model the optical extinction and X-ray scattering properties of intergalactic dust grains to constrain the intergalactic opacity using a combined analysis of observed quasar colours and the soft X-ray background. Quasar colours effectively constrain the amount of intergalactic dust grains smaller than similar to 0.2 mu m, to the point where we expect the corresponding systematic error in the Type Ia supernova magnituderedshift relation to be sub-dominant. Soft X-ray background observations are helpful in improving the constraints on very large dust grains for which the amount of optical reddening is very small and therefore is more difficult to correct for. Our current upper limit corresponds to similar to 0.25 mag dimming at optical wavelengths for a source at redshift z = 1, which is too small to alleviate the need for dark energy but large in terms of relative error. However, we expect it to be possible to lower this bound considerably with an improved understanding of the possible sources of the X-ray background, in combination with observations of compact X-ray sources such as active galactic nuclei.

Place, publisher, year, edition, pages
2012. Vol. 426, no 4, 3360-3368 p.
Keyword [en]
scattering, dust, extinction, intergalactic medium, cosmology: theory
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-83013DOI: 10.1111/j.1365-2966.2012.21940.xISI: 000310064400053OAI: oai:DiVA.org:su-83013DiVA: diva2:574441
Note

AuthorCount:2;

Available from: 2012-12-05 Created: 2012-12-03 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Sources of Dust Extinction in Type Ia Supernovae: Measurements and constraints from X-rays to the Infrared
Open this publication in new window or tab >>Sources of Dust Extinction in Type Ia Supernovae: Measurements and constraints from X-rays to the Infrared
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of Type Ia supernovae (SNe Ia) as distance indicators is essential for studying the expansion history of the Universe and for exploring the nature of dark energy. However, a lack of understanding of the progenitor systems and the empirically derived colour-brightness corrections represent severe limitations for SNe Ia as cosmological probes. In this thesis, we study how dust along the line of sight towards SNe Ia affects the observed light over a wide range of wavelengths; from X-rays to infrared.

Unless properly corrected for, the existence of intergalactic dust will introduce a redshift dependent magnitude offset to standard candle sources and bias the cosmological parameter estimates as derived from observations of SNe Ia. We model the optical extinction and X-ray scattering properties of intergalactic dust grains to constrain the intergalactic opacity using a combined analysis of observed quasar colours and measurements of the soft X-ray background. We place upper limits on the extinction AB(z = 1) < 0.10 - 0.25 mag, and the dust density parameter Ωdust < 105 − 10(ρgrain/3 g cm3), for models with RV < 12 − ∞, respectively.

Dust in the host galaxies, and dust that may reside in the circumstellar (CS) environment, have important implications for the observed colours of SNe Ia. Using the Hubble Space Telescope and several ground based telescopes, we measure the extinction law, from UV to NIR, for a sample of six nearby SNe Ia. The SNe span a range of E(B − V ) ≈ 0.1 − 1.4 mag and RV  ≈ 1.5 − 2.7, showing a diversity of dust extinction parameters. We present mid- and far-infrared (IR) observations for a number of SNe Ia, obtained with the Herschel Space Observatory and Spitzer Space Telescope, addressing CS dust as an explanation for “peculiar” extinction towards some SNe Ia. No excess IR emission is detected, limiting CS dust masses, Mdust < 105 solar masses. In particular, the timely appearance of SN 2014J in M82 - the closest SN Ia in several decades - allows for detailed studies, across an unprecedented wavelength range, of its lightcurve and spectral evolution along with the host galaxy and CS environment.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2015. 78 p.
Keyword
supernovae, interstellar dust, circumstellar dust, cosmology
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-111157 (URN)978-91-7649-071-6 (ISBN)
Public defence
2015-02-05, FB52, Albanova University Center, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Manuscript. Paper 6: Manuscript.

Available from: 2015-01-14 Created: 2014-12-23 Last updated: 2017-09-08Bibliographically approved

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