Preliminary Target Selection for the DESI Bright Galaxy Survey (BGS)

Ruiz-Macias, Omar; Zarrouk, Pauline; Cole, Shaun; Norberg, Peder; Baugh, C. M.; Brooks, D.; Dey, Arjun; Duan, Yutong; Eftekharzadeh, Sarah; Eisenstein, Daniel J.; Forero-Romero, Jaime E.; Gaztañaga, E.; Hahn, ChangHoon; Kehoe, R.; Landriau, Martin; Lang, Dustin; Levi, Michael; Lucey, J. R.; Meisner, Aaron M.; Moustakas, John; Myers, Adam D.; Palanque-Delabrouille, N.; Poppett, Claire; Prada, Francisco; Raichoor, Anand; Schlegel, David J.; Schubnell, M.; Tarlè, G.; Weinberg, David H.; Wilson, Michael J.; Yèche, Ch

doi:10.3847/2515-5172/abc25a

Cited by 56 publications

(34 citation statements)

References 9 publications

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“…The resulting catalogue is defined in Ruiz-Macias et al (2020) and here we present the details of that selection and associated analysis of the catalogue. This BGS catalogue was used by DESI in the commissioning stage of the early survey validation observations.…”

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confidence: 99%

Characterizing the target selection pipeline for the Dark Energy Spectroscopic Instrument Bright Galaxy Survey

Ruiz-Macias

Zarrouk

Cole

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present the steps taken to produce a reliable and complete input galaxy catalogue for the Dark Energy Spectroscopic Instrument (DESI) Bright Galaxy Sample (BGS) using the photometric Legacy Survey DR8 DECam. We analyze some of the main issues faced in the selection of targets for the DESI BGS, such as star-galaxy separation, contamination by fragmented stars and bright galaxies. Our pipeline utilizes a new way to select BGS galaxies using Gaia photometry and we implement geometrical and photometric masks that reduce the number of spurious objects. The resulting catalogue is cross-matched with the Galaxy and Mass Assembly (GAMA) survey to assess the completeness of the galaxy catalogue and the performance of the target selection. We also validate the clustering of the sources in our BGS catalogue by comparing with mock catalogues and SDSS data. Finally, the robustness of the BGS selection criteria are assessed by quantifying the dependence of the target galaxy density on imaging and other properties. The largest systematic correlation we find is a 7 per cent supression of the target density in regions of high stellar density.

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confidence: 99%

Characterizing the target selection pipeline for the Dark Energy Spectroscopic Instrument Bright Galaxy Survey

Ruiz-Macias

Zarrouk

Cole

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…Spectroscopic redshifts for z ≲ 0.2 SN bring the bias under control. One possibility for carrying this out is through the secondary target program of the DESI Bright Galaxy Survey [21], or other multifiber spectrographs [22,23]. Such a low redshift spectroscopic SN sample is quite interesting scientifically as it also has power as a cosmic probe of gravity through peculiar velocities [24,25].…”

Section: Discussionmentioning

confidence: 99%

Cosmology requirements on supernova photometric redshift systematics for the Rubin LSST and Roman Space Telescope

Mitra

Linder

2021

Phys. Rev. D

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Some million type Ia supernovae (SN) will be discovered and monitored during upcoming wide area time domain surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). For cosmological use, accurate redshifts are needed among other characteristics; however the vast majority of the SN will not have spectroscopic redshifts, even for their host galaxies, only photometric redshifts. We assess the redshift systematic control necessary for robust cosmology. Based on the photometric vs true redshift relation generated by machine learning applied to a simulation of 500,000 galaxies as observed with LSST quality, we quantify requirements on systematics in the mean relation and in the outlier fraction and deviance so as not to bias dark energy cosmological inference. Certain redshift ranges are particularly sensitive, motivating spectroscopic followup of SN at z ≲ 0.2 and around z ≈ 0.5-0.6. Including Nancy Grace Roman Space Telescope near infrared bands in the simulation, we reanalyze the constraints, finding improvements at high redshift but little at the low redshifts where systematics lead to strong cosmology bias. We identify a complete spectroscopic survey of SN host galaxies for z ≲ 0.2 as a highly favored element for robust SN cosmology.

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“…The number of host redshifts in this hypothetical sample is predicted using a Semi-Analytic galaxy simulation. Although hypothetical, Section 3.2.2 of Howlett et al (2017c) demonstrates that the expected target density (∼ 900 deg −2 ) would be comparable to DESI BGS (Ruiz-Macias et al 2020). It is approximately one magnitude deeper than the above proposed 4MOST Hemisphere Survey, but could be considered as either a rough combination of this and other confirmed 4MOST Consortium surveys (de Jong et al 2019;Driver et al 2019;Finoguenov et al 2019;Merloni et al 2019;Richard et al 2019), or a possible extension to these towards the end of the LSST timeline.…”

Section: Lsst and J < 19 Samplementioning

confidence: 98%

Using peculiar velocity surveys to constrain neutrino masses

Whitford,

Howlett,

Davis

2021

Preprint

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The presence of massive neutrinos in the early Universe is expected to have influenced the observed distribution of galaxies, and their observed motions. In this work, we explore whether measurements of galaxy peculiar velocities could allow us to improve upon neutrino mass constraints from galaxy redshift surveys alone. Using Fisher matrix forecasts, we show that the galaxy peculiar motions do contain information on the sum of the masses of neutrinos 𝑚 𝜈 , and that this information can be used to improve upon constraints that may be obtained from low-redshift galaxy surveys (𝑧 < 0.5) combined with Planck measurements of the Cosmic Microwave Background. Compared to the full constraining power offered by Planck and higher redshift DESI/Euclid data, we find that the benefit of including peculiar velocities only marginally improves neutrino mass constraints. However, when one is limited to modeling only quasi-linear scales, adds additional degrees of freedom via a varying number of effective neutrino species (𝑁 eff ), or does not include information from Planck, our results show that the inclusion of peculiar velocity measurements can still substantially improve upon the constraints. As such, we demonstrate that it may be possible to achieve upper bounds on 𝑚 𝜈 (𝜎 𝑚 𝜈 = 0.051 eV; 68% confidence limit) comparable to those from Planck, from spectroscopic galaxy surveys alone, as long as the peculiar velocity data is available. This could allow for an independent comparison between constraints on 𝑚 𝜈 from the early-and late-time Universe probes that are particularly timely given current cosmological parameter tensions.

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Preliminary Target Selection for the DESI Bright Galaxy Survey (BGS)

Cited by 56 publications

References 9 publications

Characterizing the target selection pipeline for the Dark Energy Spectroscopic Instrument Bright Galaxy Survey

Characterizing the target selection pipeline for the Dark Energy Spectroscopic Instrument Bright Galaxy Survey

Cosmology requirements on supernova photometric redshift systematics for the Rubin LSST and Roman Space Telescope

Using peculiar velocity surveys to constrain neutrino masses

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