Galaxy Alignments with Surrounding Structure in the Sloan Digital Sky Survey

Dhvanil D. Desai; Barbara S. Ryden

doi:10.3847/1538-4357/ac83a8

paper

Galaxy Alignments with Surrounding Structure in the Sloan Digital Sky Survey

arXiv:2012.02254 · doi:10.3847/1538-4357/ac83a8

Abstract

Using data from the Sloan Digital Sky Survey (SDSS) Legacy Survey, we study the alignment of luminous galaxies with spectroscopic data with the surrounding larger-scale structure as defined by galaxies with only photometric data. We find that galaxies from the red sequence have a statistically significant tendency for their apparent long axes to align parallel to the projected surrounding structure. Red galaxies more luminous than the median of our sample ( $M_{r} < - 21.78$ ) have a mean alignment angle $⟨ Φ ⟩ < 4 5^{\circ}$ , indicating preferred parallel alignment, at a significance level $> 4.5 σ$ on projected scales $0.1 Mpc < r_{p} \leq 7.5 Mpc$ . Fainter red galaxies have $⟨ Φ ⟩ < 4 5^{\circ}$ at a significance level $> 4.3 σ$ at scales $1 Mpc < r_{p} < 3 Mpc$ . At a projected scale $r_{p} = 3.0 Mpc$ , the mean alignment angle decreases steadily with increasing luminosity for red galaxies with $M_{r} ≲ - 22.5$ , reaching $⟨ Φ ⟩ = 40.4 9^{\circ} \pm 0.5 6^{\circ}$ for the most luminous one percent ( $M_{r} \sim - 23.57$ ). Galaxies from the blue sequence show no statistically significant tendency for their axes to align with larger-scale structure, regardless of galaxy luminosity. Galaxies in higher-density regions do not show a statistically significant difference in mean alignment angle from galaxies in lower-density regions; this holds true for the faint blue, luminous blue, faint red, and luminous red subsets.

arXiv comment12 pages, 5 figures, 2 tables, submitted to ApJ

Galaxy Alignments with Surrounding Structure in the Sloan Digital Sky Survey

Abstract

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