X-RAY MONITORING OF GRAVITATIONAL LENSES WITH<i>CHANDRA</i>

Chen, Bin; Dai, Xinyu; Kochanek, C. S.; Chartas, G.; Blackburne, Jeffrey A.; Morgan, Christopher W.

doi:10.1088/0004-637x/755/1/24

Cited by 72 publications

(112 citation statements)

References 81 publications

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“…Finally, there is the relationship between the dust-to-gas ratio (δ DGR ) and metallicity seen in nearby galaxies (e.g., Issa et al 1990;Dwek 1998;Edmunds 2001;Inoue 2003;; Leroy et al 2011). Attempts to measure the dust-to-gas ratios of high-redshift galaxies support a similar correlation, as well as a trend toward smaller δ DGR at higher redshifts (Saintonge et al 2013;Chen et al 2013).…”

Section: Introductionmentioning

confidence: 94%

“…It is now accepted both from observations and interstellar medium evolution models that δ DGR scales linearly with the oxygen abundance (e.g., Issa et al 1990;Dwek 1998;Edmunds 2001;Inoue 2003;Leroy et al 2011;Saintonge et al 2013;Chen et al 2013). Nevertheless, the measurement of the dust-to-gas mass ratio, in particular, in highredshift galaxies remains very uncertain because of a number of assumptions that need to be made to achieve a δ DGR measurement.…”

Section: Dust-to-gas Ratiomentioning

confidence: 99%

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Molecular gas content in strongly lensedz~ 1.5−3 star-forming galaxies with low infrared luminosities

Dessauges‐Zavadsky

Zamojski

Schaerer

et al. 2015

A&A

110

126

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To extend the molecular gas measurements to more typical star-forming galaxies (SFGs) with star formation rates SFR < 40 M yr −1 and stellar masses M * < 2.5 × 10 10 M at z ∼ 1.5−3, we have observed CO emission with the IRAM Plateau de Bure Interferometer and the IRAM 30 m telescope for five strongly lensed galaxies, selected from the Herschel Lensing Survey. These observations are combined with a compilation of CO measurements from the literature. From this, we infer the CO luminosity correction factors r 2,1 = 0.81 ± 0.20 and r 3,1 = 0.57 ± 0.15 for the J = 2 and J = 3 CO transitions, respectively, valid for SFGs at z > 1. The combined sample of CO-detected SFGs at z > 1 shows a large spread in star formation efficiency (SFE) with a dispersion of 0.33 dex, such that the SFE extends well beyond the low values of local spirals and overlaps the distribution of z > 1 submm galaxies. We find that the spread in SFE (or equivalently in molecular gas depletion timescale) is due to the variations of several physical parameters, primarily the specific star formation rate, and also stellar mass and redshift. The dependence of SFE on the offset from the main sequence and the compactness of the starburst is less clear. The possible increase of the molecular gas depletion timescale with stellar mass, now revealed by low M * SFGs at z > 1 and also observed at z = 0, contrasts with the generally acknowledged constant molecular gas depletion timescale and refutes the linearity of the Kennicutt-Schmidt relation. A net rise of the molecular gas fraction ( f gas ) is observed from z ∼ 0.2 to z ∼ 1.2, followed by a very mild increase toward higher redshifts, as found in earlier studies. At each redshift the molecular gas fraction shows a large dispersion, mainly due to the dependence of f gas on stellar mass, producing a gradient of increasing f gas with decreasing M * . We provide the first measurement of the molecular gas fraction of z > 1 SFGs at the low-M * end between 10 9.4 < M * /M < 10 9.9 , reaching a mean f gas = 0.69 ± 0.18, which shows a clear f gas upturn at these lower stellar masses. Finally, we find evidence for a nonuniversal dust-to-gas ratio among high-redshift SFGs, high-redshift submm galaxies, local spirals, and local ultraluminous IR galaxies with near-solar metallicities, as inferred from a homogeneous analysis of their rest-frame 850 μm luminosity per unit gas mass. The SFGs with z > 1 show a trend for a lower L ν (850 μm)/M gas mean by 0.33 dex compared to the other galaxy populations.

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Section: Introductionmentioning

confidence: 94%

Section: Dust-to-gas Ratiomentioning

confidence: 99%

Molecular gas content in strongly lensedz~ 1.5−3 star-forming galaxies with low infrared luminosities

Dessauges‐Zavadsky

Zamojski

Schaerer

et al. 2015

A&A

110

126

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“…The microlensed sample is treated differently as the measurement of the physical size of the X-ray emitting region is already non-dimensionless and can be used to calculate ℓ directly, the black hole mass is therefore not required. We assume further the highest energy bin in the Chandra spectra shown in Chen et al (2012) is a lower limit on the high-energy cut-off. This is them corrected for redshift.…”

Section: Sample Selection and Data Collectionmentioning

confidence: 99%

“…This is them corrected for redshift. Finally, for the coronal luminosities of the lensed quasars we use the 0.2-50 keV luminosities reported in the Chen et al (2012) paper. These objects serve to show that distant quasars operate at values of ℓ within the range 10-100 or greater; NuSTAR observations will be required to measure their expected cutoffs and thus Θ values.…”

Section: Sample Selection and Data Collectionmentioning

confidence: 99%

Properties of AGN coronae in theNuSTARera

Fabian

Lohfink

Kara

et al. 2015

Mon. Not. R. Astron. Soc.

358

433

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The focussing optics of NuSTAR have enabled high signal-to-noise spectra to be obtained from many X-ray bright Active Galactic Nuclei (AGN) and Galactic Black Hole Binaries (BHB). Spectral modelling then allows robust characterization of the spectral index and upper energy cutoff of the coronal power-law continuum, after accounting for reflection and absorption effects. Spectral-timing studies, such as reverberation and broad iron line fitting, of these sources yield coronal sizes, often showing them to be small and in the range of 3 to 10 gravitational radii in size. Our results indicate that coronae are hot and radiatively compact, lying close to the boundary of the region in the compactness -temperature (Θ − ℓ) diagram which is forbidden due to runaway pair production. The coincidence suggests that pair production and annihilation are essential ingredients in the coronae of AGN and BHB and that they control the shape of the observed spectra.

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“…These observations were a component of a larger Chandra Cycle 11 monitoring program, the details of which are published in Chen et al (2012).…”

Section: Data and Analysismentioning

confidence: 99%

Size Measurements of the Quasar X-Ray Continuum Emission Region by Analysis of Microlensing in Chandra Imagery

MacLeod

Morgan

2013

Proc. IAU

Self Cite

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Abstract. Microlensing offers a unique way to constrain the physical extent of different emission regions in a lensed quasar, putting to test various accretion and continuum emission models. We perform a microlensing analysis using six Chandra observations (spanning six years) of the lensed quasar SDSS 0924+0219 (redshift zs = 1.52), in which X-ray microlensing variability is detected with high confidence. The system exhibits pronounced microlensing variability in the X-rays compared to the optical, indicating a comparatively small extent of r 1 / 2 < 3.8 × 10 14 cm (95% confidence) for the X-ray continuum emitting region, near the inner edge of the accretion disk.

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X-RAY MONITORING OF GRAVITATIONAL LENSES WITHCHANDRA

Cited by 72 publications

References 81 publications

Molecular gas content in strongly lensedz~ 1.5−3 star-forming galaxies with low infrared luminosities

Molecular gas content in strongly lensedz~ 1.5−3 star-forming galaxies with low infrared luminosities

Properties of AGN coronae in theNuSTARera

Size Measurements of the Quasar X-Ray Continuum Emission Region by Analysis of Microlensing in Chandra Imagery

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