BHM Ancillary Programs

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aSummary

The BHM project has a number of ancillary spectroscopic programs, which provide scientifically interesting targets when BOSS fibers are not assigned to core science projects. These have the goal of obtaining redshifts and classifications for candidate QSOs and bright galaxies selected via wide-area optical/IR surveys. These supplementary programs do not affect the overall SDSS-V MOS survey plan (allocation of exposure resources across the sky).

Gaia-unWISE AGN survey

Sky map of Gaia-unWISE QSO target density
Sky density of Gaia unWISE QSO targets selected as candidates for observation in dark time (v0.5.3 targeting)

This BHM-led program collects BOSS spectroscopy for a large sample of candidate QSOs. We downselect targets suitable for SDSS-V spectroscopy from the parent sample presented by Shu et al. (2019), who used applied a machine-learning approach to a combination of the Gaia DR2 and unWISE catalogues. The Gaia-unWISE AGN targets are distributed across almost the entire sky (except for the innermost Galactic plane and regions around the Magellanic Clouds), and so are well matched to the SDSS-V all-sky survey strategy. This is primarily a discovery program, and so we have excluded AGN targets having existing good quality optical spectroscopy in earlier SDSS iterations.

Bright Low-Redshift Galaxy Survey

This program seeks to measure redshifts and provide classifications for a sample of optically bright, low-redshift, morphologically resolved galaxies, selected from legacysurvey.org/dr8 optical/IR catalogues. This program is primarily intended as a filler, with no expectation of a high degree of spectroscopic completeness.

BHM Carton for FPS Commissioning

In order to support FPS commissioning tests, we defined a carton (manual_bhm_spiders_comm) of X-ray selected targets having known redshifts. These targets were drawn from the eFEDS/SDSS-V sample presented by Aydar, et al (2025). This carton was used to check the ability of the whole SDSS-V system (telescope, FPS, spectrograph and data reduction pipelines) to collect reliable redshifts for SPIDERS-like targets. This carton is not part of any targeting generation because it was never used within a robostrategy run.

Observational goals and requirements

The SDSS-V/BHM Ancillary projects seek to gather spectroscopic redshifts and classifications for large samples of candidate QSOs and galaxies.

These samples generally have only moderate surface density on the sky, and so benefit most from the widest area components of the SDSS-V survey.

Target selection and survey implementation

Further details of the algorithms and criteria used to select BHM ancillary target cartons are provided via the links below.

Targeting generations used in early FPS operations

The ‘v0.5.epsilon-7-core-0’, ‘v0.5.2’, ‘v0.5.3’ and ‘v0.5.5’ targeting generations were used during initial SDSS-V/FPS operations (2022-2023). These generations are identical from the point of view of BHM Ancillary program targeting.

Below is a list of BHM Ancillary cartons that were considered (the carton names link to detailed descriptions):

Targeting generation used during SDSS-V plate operations

The ‘v0.plates’ targeting generation was used during the first year of SDSS-V operations at APO when the old plug plate system was still in place. We included early versions of the Gaia/unWISE AGN cartons during this phase.

Below is a list of BHM Ancillary cartons that were considered (the carton names link to detailed descriptions):

BHM-centric open fiber programs

A subset of the SDSS-V Open Fiber Program focus on BOSS (re-)observations of optical/IR/X-ray selected QSOs/AGN, and so have strong overlap with BHM’s core science themes. The carton names for these six open fiber programs are listed below.

The Open Fiber programs were not used during the SDSS-V plate program.

Spectroscopic data released in DR19

The sky density of BHM GUA targets having at least one spectrum in DR19.
The sky density of BHM bright low-z galaxy targets having at least one spectrum in DR19.
The sky density of BHM-related openfiber targets having at least one spectrum in DR19.

The number of BHM Ancillary and BHM-centric open fiber program spectra in DR19 are given in the table below.

(First)Carton name“daily” coadd spectra“epoch” coadd spectra“allepoch” coadd spectra Unique targets
bhm_gua_bright26773237351495115307
bhm_gua_dark22897182591217812723
bhm_colr_galaxies_lsdr88812775762236328
openfibertargets_nov2020_274373416128093899
openfibertargets_nov2020_332018199915181875
manual_bhm_spiders_comm1420355291355
openfibertargets_nov2020_18799777361717
openfibertargets_nov2020_1162460458596
openfibertargets_nov2020_261616816
Number of SDSS DR19 BOSS BHM Ancillary and Open Fiber spectra associated with each ancillary BHM carton (considering only the FIRSTCARTON label for each spectrum). Target uniqueness is determined via SDSS_ID.

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