OzDES multifibre spectroscopy for the Dark Energy Survey: 3-yr results and first data release

Childress, M.; Lidman, C.; Davis, Tamara M.; Tucker, B. E.; Asorey, J.; Yuan, F.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Banerji, M.; Benoit-Lévy, A.; Bernard, Stephanie R.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Rosell, A. Carnero; Carollo, D.; Kind, M. Carrasco; Carretero, J.; Castander, F. J.; Cunha, C. E.; Costa, L. N. da; D’Andrea, C. B.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.; Foley, R. J.; Fosalba, P.; Frieman, Joshua A.; García-Bellido, J.; Glazebrook, Karl; Goldstein, D.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gupta, R.; Gutiérrez, G.; Hinton, S. R.; Hoormann, J. K.; James, D. J.; Keßler, R.; Kim, Alex; King, A.; Kovacs, E.; Kuêhn, K.; Kuhlmann, S.; Kuropatkin, N.; Lagattuta, David J.; Lewis, Geraint F.; Li, T. S.; Lima, M.; Lin, Huan; Macaulay, E.; Maia, M. A. G.; Marriner, J.; March, M.; Marshall, J. L.; Martini, Paul; McMahon, R. G.; Menanteau, F.; Miquel, R.; Möller, A.; Morganson, E.; Mould, Jeremy; Mudd, D.; Muthukrishna, Daniel; Nichol, R. C.; Nord, B.; Ogando, R. L. C.; Ostrovski, F.; Parkinson, David; Plazas, A. A.; Reed, S. L.; Reil, K.; Romer, A. K.; Rykoff, E. S.; Šako, M.; Sánchez, E.; Scarpine, V.; Schindler, R. H.; Schubnell, M.; Scolnic, D.; Sevilla-Noarbe, I.; Seymour, N.; Sharp, Robert; Smith, M.; Soares-Santos, M.; Sobreira, F.; Sommer, N. E.; Spinka, H.; Suchyta, E.; Sullivan, M.; Swanson, M. E. C.; Tarlè, G.; Uddin, S. A.; Walker, A. R.; Wester, W.; Zhang, B.

doi:10.1093/mnras/stx1872

Cited by 95 publications

(90 citation statements)

References 50 publications

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“…These were calculated both through internal dispersion within the catalogue, and by comparison with external catalogues. This magnitude of uncertainty was again confirmed in Childress et al (2017) who measured an rms dispersion in redshift recovery of σ z = 4.2 × 10 −4 between initial science-quality redshift measurements (qop=3), and subsequent higher signal-to-noise measurements of the same source (qop=4).The uncertainties are calculated as weighted pair-wise redshift differences, σ z = ∆z/(1 + z), which means that at z ∼ 1 the uncertainties are not 4 × 10 −4 but 8 × 10 −4 after multiplying by (1 + z).…”

Section: Spectrograph Resolution and Redshift Measurementsupporting

confidence: 60%

Can redshift errors bias measurements of the Hubble Constant?

Davis

Hinton

Howlett

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Redshifts have been so easy to measure for so long that we tend to neglect the fact that they too have uncertainties and are susceptible to systematic error. As we strive to measure cosmological parameters to better than 1% it is worth reviewing the accuracy of our redshift measurements. Surprisingly small systematic redshift errors, as low as 10 −4 , can have a significant impact on the cosmological parameters we infer, such as H 0 . Here we investigate an extensive (but not exhaustive) list of ways in which redshift estimation can go systematically astray. We review common theoretical errors, such as adding redshifts instead of multiplying by (1 + z); using v = cz; and using only cosmological redshift in the estimates of luminosity and angular-diameter distances. We consider potential observational errors, such as rest wavelength precision, air to vacuum conversion, and spectrograph wavelength calibration. Finally, we explore physical effects, such as peculiar velocity corrections, galaxy internal velocities, gravitational redshifts, and overcorrecting within a bulk flow. We conclude that it would be quite easy for small systematic redshift errors to have infiltrated our data and be impacting our cosmological results. While it is unlikely that these errors are large enough to resolve the current H 0 tension, it remains possible, and redshift accuracy may become a limiting factor in near future experiments. With the enormous efforts going into calibrating the vertical axis of our plots (standard candles, rulers, clocks, and sirens) we argue that it is now worth paying a little more attention to the horizontal axis (redshifts).

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Section: Spectrograph Resolution and Redshift Measurementsupporting

confidence: 60%

Can redshift errors bias measurements of the Hubble Constant?

Davis

Hinton

Howlett

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…As part of the supernova search, 30 square degrees are be repeatedly observed on an approximately weekly cadence in the g, r, i, and z filters for the duration of DES, amounting to 20-30 epochs per filter per year (Kessler et al 2015). In these fields, we also have a set of spectroscopically verified quasars from the OzDES program (Australian DES/optical redshifts for DES; Yuan et al 2015;Childress et al 2017) as part of the DES and OzDES reverberation mapping project. This project photometrically and spectroscopically monitors 771 quasars in order to measure the masses of their SMBHs (King et al 2015).…”

Section: Observationsmentioning

confidence: 99%

“…These quasars are as faint as 23.6 in g and were selected heterogeneously with a broad range of quasar detection techniques (e.g., Banerji et al 2015;Tie et al 2017). From the combination of these two surveys, we use the first three years of photometry and spectra for the 771 quasars that we continue to monitor (Diehl et al 2016;Childress et al 2017). …”

Section: Observationsmentioning

confidence: 99%

Quasar Accretion Disk Sizes from Continuum Reverberation Mapping from the Dark Energy Survey

Mudd¹,

Martini²,

Zu³

et al. 2018

ApJ

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We present accretion disk size measurements for 15 luminous quasars at 0.7z1.9 derived from griz light curves from the Dark Energy Survey. We measure the disk sizes with continuum reverberation mapping using two methods, both of which are derived from the expectation that accretion disks have a radial temperature gradient and the continuum emission at a given radius is well described by a single blackbody. In the first method we measure the relative lags between the multiband light curves, which provides the relative time lag between shorter and longer wavelength variations. From this, we are only able to constrain upper limits on disk sizes, as many are consistent with no lag the 2σ level. The second method fits the model parameters for the canonical thin disk directly rather than solving for the individual time lags between the light curves. Our measurements demonstrate good agreement with the sizes predicted by this model for accretion rates between 0.3 and 1 times the Eddington rate. Given our large uncertainties, our measurements are also consistent with disk size measurements from gravitational microlensing studies of strongly lensed quasars, as well as other photometric reverberation mapping results, that find disk sizes that are a factor of a few (∼3) larger than predictions.

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“…The survey is carried out using the AAOmega spectrograph (Smith et al 2004) and the Two Degree Field (2dF) 400 multi object fibre positioning system (Lewis et al 2002), which covers the wavelength range of 3700-8800Å. The primary goal of OzDES is to obtain redshifts for SN host galaxies (Yuan et al 2015;Childress et al 2017). OzDES was awarded 100 nights on the 3.9m Anglo-Australian Telescope (AAT) that were originally planned over five years.…”

Section: Observationsmentioning

confidence: 99%

“…In addition to supernova host galaxies, the OzDES survey also targets AGN for the OzDES RM program, as well as a number of other ancillary target classes (Childress et al 2017). The possible AGN targets in the DES-SN fields were selected based on colour and variability using the data from the DES Year 1 catalogues, DES Y1A1.…”

Section: Ozdes Reverberation Mapping Candidatesmentioning

confidence: 99%

C iv black hole mass measurements with the Australian Dark Energy Survey (OzDES)

Hoormann¹,

Martini²,

Davis³

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Black hole mass measurements outside the local universe are critically important to derive the growth of supermassive black holes over cosmic time, and to study the interplay between black hole growth and galaxy evolution. In this paper we present two measurements of supermassive black hole masses from reverberation mapping (RM) of the broad C iv emission line. These measurements are based on multi-year photometry and spectroscopy from the Dark Energy Survey Supernova Program (DES-SN) and the Australian Dark Energy Survey (OzDES), which together constitute the OzDES RM Program. The observed reverberation lag between the DES continuum photometry and the OzDES emission-line fluxes is measured to be 358 +126 −123 and 343 +58 −84 days for two quasars at redshifts of 1.905 and 2.593 respectively. The corresponding masses of the two supermassive black holes are 4.4 × 10 9 and 3.3 × 10 9 M , which are among the highest-redshift and highest-mass black holes measured to date with RM studies. We use these new measurements to better determine the C iv radius−luminosity relationship for high-luminosity quasars, which is fundamental to many quasar black hole mass estimates and demographic studies.

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OzDES multifibre spectroscopy for the Dark Energy Survey: 3-yr results and first data release

Cited by 95 publications

References 50 publications

Can redshift errors bias measurements of the Hubble Constant?

Can redshift errors bias measurements of the Hubble Constant?

Quasar Accretion Disk Sizes from Continuum Reverberation Mapping from the Dark Energy Survey

C iv black hole mass measurements with the Australian Dark Energy Survey (OzDES)

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