부산대학교 도서관

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 $\langle \Phi \rangle < 45^{\circ}$, indicating preferred parallel alignment, at a significance level $>4.5 \sigma$ on projected scales $0.1\,\mathrm{Mpc} < r_p \leq 7.5\,\mathrm{Mpc}$. Fainter red galaxies have $\langle \Phi \rangle < 45^{\circ}$ at a significance level $>4.3\sigma$ at scales $1\,\mathrm{Mpc} < r_p < 3\,\mathrm{Mpc}$. At a projected scale $r_p = 3.0\,\mathrm{Mpc}$, the mean alignment angle decreases steadily with increasing luminosity for red galaxies with $M_r \lesssim -22.5$, reaching $\langle \Phi \rangle = 40.49^{\circ} \pm 0.56^{\circ}$ 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.
Comment: 12 pages, 5 figures, 2 tables, submitted to ApJ