Extinction curve template for intrinsically reddened quasars

Zafar, T.; Møller, P.; Watson, Derrick G.; Fynbo, J. P. U.; Krogager, J.-K.; Zafar, Nousheen; Saturni, Francesco Gabriele; Geier, S.; Venemans, Bram

doi:10.1051/0004-6361/201526570

Cited by 53 publications

(90 citation statements)

References 57 publications

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“…Evidence for curves steeper than the SMC average has been observed along certain sightlines within the SMC (Gordon et al 2003), in the Milky Way and some Local Group galaxies (Gordon et al 2003(Gordon et al , 2009Sofia et al 2005;Amanullah et al 2014), and in quasars (e.g., Hall et al 2002;Jiang et al 2013;Zafar et al 2015). Our results, combined with those in the literature, suggest that such steep curves may be typical of low-mass and young galaxies at high redshift.…”

Section: Young/low-mass Galaxiessupporting

confidence: 79%

“…In any case, curves steeper than the SMC may be possible with a paucity of large dust grains and/or an overabundance of silicate grains (Zafar et al 2015). In particular, large dust grains may be efficiently destroyed by SN shock waves (Draine & Salpeter 1979;McKee 1989;Jones 2004), which would have the effect of steepening the dust curve (i.e., such that proportionally more light is absorbed in the UV relative to the optical).…”

Section: Young/low-mass Galaxiesmentioning

confidence: 99%

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The HDUV Survey: A Revised Assessment of the Relationship between UV Slope and Dust Attenuation for High-redshift Galaxies

Reddy

Oesch

Bouwens

et al. 2018

ApJ

217

279

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We use a newly assembled sample of 3545 star-forming galaxies with secure spectroscopic, grism, and photometric redshifts at z=1.5-2.5 to constrain the relationship between UV slope (β) and dust attenuation (L IR /L UV ≡IRX). Our sample significantly extends the range of L UV and β probed in previous UV-selected samples, including those as faint as M 1600 =−17.4 ( L 0.05 UV *  ) and −2.6β0.0. IRX is measured using stacks of deep Herschel data, and the results are compared with predictions of the IRX−β relation for different assumptions of the stellar population model and obscuration curve. We find that z=1.5-2.5 galaxies have an IRX −β relation that is consistent with the predictions for an SMC curve if we invoke subsolar-metallicity models currently favored for high-redshift galaxies, while the commonly assumed starburst curve overpredicts the IRX at a given β by a factor of 3. IRX is roughly constant with L UV for L UV 3×109 L e . Thus, the commonly observed trend of fainter galaxies having bluer β may simply reflect bluer intrinsic slopes for such galaxies, rather than lower obscurations. The IRX−β relation for young/low-mass galaxies at z2 implies a dust curve that is steeper than the SMC. The lower attenuations and higher ionizing photon output for low-metallicity stellar populations point to Lyman continuum production efficiencies, ξ ion , that may be elevated by a factor of ≈2 relative to the canonical value for L * galaxies, aiding in their ability to keep the universe ionized at z∼2.

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Section: Young/low-mass Galaxiessupporting

confidence: 79%

Section: Young/low-mass Galaxiesmentioning

confidence: 99%

The HDUV Survey: A Revised Assessment of the Relationship between UV Slope and Dust Attenuation for High-redshift Galaxies

Reddy

Oesch

Bouwens

et al. 2018

ApJ

217

279

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“…In Table 1 we show the redshifts, both spectroscopic and photometric, along with the calculated reddening, A V , both assuming SMC-like extinction and the extinction curve found by Zafar et al (2015), and the corresponding reddening in terms of E(B − V). The notes list the specific colors in which the individual objects do not meet the HAQ criteria.…”

Section: Resultsmentioning

confidence: 99%

“…For the object CQ095924.4+020842.6 the composite is overplotted at the photometrically computed redshift (z phot = 1.15) since no emission line features are unambiguously present in the spectrum. The amount of reddening for each of the objects was calculated assuming both an SMC-like extinction curve and a steeper extinction curve for intrinsically reddened quasars (Zafar et al 2015). For the SMC we used the extinction curve as described by Gordon et al (2003), but with a modification for wavelengths greater than 4400 Å (Fitzpatrick & Massa 2005), following the same procedure as in Urrutia et al (2009);Fynbo et al (2013).…”

Section: Spectroscopic Analysismentioning

confidence: 99%

Determining the fraction of reddened quasars in COSMOS with multiple selection techniques from X-ray to radio wavelengths

Heintz

Fynbo

Møller

et al. 2016

A&A

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The sub-population of quasars reddened by intrinsic or intervening clouds of dust are known to be underrepresented in optical quasar surveys. By defining a complete parent sample of the brightest and spatially unresolved quasars in the COSMOS field, we quantify to which extent this sub-population is fundamental to our understanding of the true population of quasars. By using the available multiwavelength data of various surveys in the COSMOS field, we built a parent sample of 33 quasars brighter than J = 20 mag, identified by reliable X-ray to radio wavelength selection techniques. Spectroscopic follow-up with the NOT/ALFOSC was carried out for four candidate quasars that had not been targeted previously to obtain a 100% redshift completeness of the sample. The population of high A V quasars (HAQs), a specific sub-population of quasars selected from optical/near-infrared photometry, some of which were shown to be missed in large optical surveys such as SDSS, is found to contribute 21% +9 −5 of the parent sample. The full population of bright spatially unresolved quasars represented by our parent sample consists of 39% +9 −8 reddened quasars defined by having A V > 0.1, and 21% +9 −5 of the sample having E(B − V) > 0.1 assuming the extinction curve of the Small Magellanic Cloud. We show that the HAQ selection works well for selecting reddened quasars, but some are missed because their optical spectra are too blue to pass the g − r color cut in the HAQ selection. This is either due to a low degree of dust reddening or anomalous spectra. We find that the fraction of quasars with contributing light from the host galaxy, causing observed extended spatial morphology, is most dominant at z 1. At higher redshifts the population of spatially unresolved quasars selected by our parent sample is found to be representative of the full population of bright active galactic nuclei at J < 20 mag. This work quantifies the bias against reddened quasars in studies that are based solely on optical surveys.

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“…We are therefore lead to consider their other scenariowhere the dust cloud is a clump in an "Accreting Torus" much closer to the central engine (Jiang et al 2013;Zafar et al 2015).…”

Section: Absorbing Cloud Propertiesmentioning

confidence: 99%

The Optical Variability of SDSS Quasars From Multi-Epoch Spectroscopy. Iii. A Sudden Uv Cutoff in Quasar SDSS J2317+0005

Guo

Malkan

et al. 2016

ApJ

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We have collected near-infrared to X-ray data of 20 multi-epoch heavily reddened SDSS quasars to investigate the physical mechanism of reddening. Of these, J2317+0005 is found to be a UV cutoff quasar. Its continuum, which usually appears normal, decreases by a factor 3.5 at 3000 Å, compared to its more typical bright state during an interval of 23 days. During this sudden continuum cut-offthe broad emission line fluxes do not change, perhaps due to the large size of the broad-line region (BLR), r > 23/(1+z) days. The UV continuum may have suffered a dramatic drop out. However, there are some difficulties with this explanation. Another possibility is that the intrinsic continuum did not changebut was temporarily blocked out, at least toward our line of sight. As indicated by X-ray observations, the continuum rapidly recovers after 42 days. A comparison of the bright state and dim states would imply an eclipse by a dusty cloud with a reddening curve having a remarkably sharp rise shortward of 3500 Å. Under the assumption of being eclipsed by a Keplerian dusty cloud, we characterized the cloud size with our observations, however, which is a little smaller than the 3000 Å continuum-emitting size inferred from accretion disk models. Therefore, we speculate that this is due to a rapid outflow or inflow with a dusty cloud passing through our line of sight to the center.

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Extinction curve template for intrinsically reddened quasars

Cited by 53 publications

References 57 publications

The HDUV Survey: A Revised Assessment of the Relationship between UV Slope and Dust Attenuation for High-redshift Galaxies

The HDUV Survey: A Revised Assessment of the Relationship between UV Slope and Dust Attenuation for High-redshift Galaxies

Determining the fraction of reddened quasars in COSMOS with multiple selection techniques from X-ray to radio wavelengths

The Optical Variability of SDSS Quasars From Multi-Epoch Spectroscopy. Iii. A Sudden Uv Cutoff in Quasar SDSS J2317+0005

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