DESI Emission-line Galaxies: Clustering Dependence on Stellar Mass and [OII] Luminosity

TL;DR

The study uses the DESI One-Percent Survey to model the clustering of ELGs as a function of stellar mass and [OII] luminosity within a CCMD-based halo framework, constraining how centrals and satellites populate halos. The analysis finds ELGs predominantly reside in a narrow halo-mass range around $M_h ightarrow$ $10^{12.2-12.4}\,h^{-1}M_han$, with low satellite fractions and modest dependence on $M_*$, while a modest, redshift-dependent $L_{ m [OII]}$–bias relation emerges at $1.2<z<1.6$. Measurement scatter in $M_*$ and imperfect [OII] as a star-formation proxy limit strong detection of property trends, but the CCMD model captures the main occupation statistics and predicts derived quantities such as bias and halo masses. The results inform mock catalog construction and provide a foundation for refining ELG-based cosmological analyses with future DESI data and upcoming surveys like Euclid and the Roman Space Telescope.

Abstract

We measure the projected two-point correlation functions of emission-line galaxies (ELGs) from the Dark Energy Spectroscopic Instrument (DESI) One-Percent Survey and model their dependence on stellar mass and [OII] luminosity. We select $\sim$180,000 ELGs with redshifts of $0.8 < z < 1.6$ and define 27 samples according to cuts in redshift and both galaxy properties. Following a framework that describes the conditional [OII] luminosity-stellar mass distribution as a function of halo mass, we simultaneously model the clustering measurements of all samples at fixed redshift. Based on the modeling result, most ELGs in our samples are classified as central galaxies, residing in halos of a narrow mass range with a typical median of $\sim$10$^{12.2-12.4}$ $h^{-1} M_\odot$. We observe a weak dependence of clustering amplitude on stellar mass, which is reflected in the model constraints and is likely a consequence of the 0.5 dex measurement uncertainty in the stellar mass estimates. The model shows a trend between galaxy bias and [OII] luminosity at high redshift ($1.2 < z < 1.6$) that is otherwise absent at lower redshifts.

Figures (18)

• Figure 1: Footprint of the 20 One-Percent Survey rosettes in blue (Mollweide projection). The Galactic plane is shown in green. The inset image shows the angular distribution of spectroscopically confirmed ELGs within one rosette; the galaxies observed in the highly complete annulus are highlighted in blue.
• Figure 2: Number density of spectroscopically confirmed ELGs in the DESI One-Percent Survey. Only galaxies within rosette annuli (Figure \ref{['fig:footprint']}) are included. Colored regions mark the redshift ranges considered in this work.
• Figure 3: Selection boundaries for the nine samples within each redshift group as a function of $\log L_{\text{[OII]}}$ and $\log M_*$. The horizontal error bars illustrate the 0.5 dex measurement scatter in stellar mass as quantified in Appendix \ref{['app:compare_cosmos']} with respect to COSMOS2020. Left, middle, and right panels correspond to redshift ranges $0.8<z<1.0$, $1.0<z<1.2$, and $1.2<z<1.6$, respectively.
• Figure 4: Measurements and fits for the nine $0.8<z<1.0$ samples defined in Figure \ref{['fig:samples']} and Table \ref{['tab:samples']}. The top-left, top-right, and bottom-left panels show the projected 2PCFs of the low-, intermediate-, and high-stellar-mass samples, respectively. Filled circles mark the measurements. Solid curves and shaded regions mark the median and $1\sigma$ bounds of the posterior model distribution, respectively. For illustrative purposes, measurements are staggered in $r_p$. Vertical offsets of $-1$ dex and $+1$ dex are applied to the lowest and highest [OII] luminosity samples in each panel, respectively. The subpanel below each main panel shows the residual of the model relative to the measurement, normalized by the measurement uncertainty. The shaded region represents the $\pm 1 \sigma$ bounds. Bottom right: measurements of the number densities are shown as filled circles, with 10% uncertainties assumed. Open circles and error bars mark the median and $1\sigma$ bounds of the posterior model distribution, respectively. For illustrative purposes, horizontal offsets are added between the measurement and fit of a given sample and between samples.
• Figure 5: Same as Figure \ref{['fig:fit_loz']} but for the $1.0<z<1.2$ intermediate-redshift samples.