Alignment between luminous red galaxies and surrounding structures at z∼ 0.5 |
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| Authors: | Emilio Donoso Ana O'Mill Diego G Lambas |
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| Institution: | Universidad Nacional de San Juan, Av. Ignacio de la Roza 590(O), 5400 San Juan, Argentina;Observatorio Astronomico Felix Aguilar, Av. Benavidez 8175(O), 5413 San Juan, Argentina;IATE, Observatorio Astronomico de la Universidad Nacional de Cordoba, Laprida 851, 5000 Cordoba, Argentina;Consejo de Investigaciones Científicas y Técnicas (CONICET), Avenida Rivadavia 1917, C1033AAJ, Buenos Aires, Argentina |
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| Abstract: | We analyse a high-redshift sample (0.4 < z < 0.5) of luminous red galaxies (LRGs) extracted from the Sloan Digital Sky Survey data release 4 and their surrounding structures to explore the presence of alignment effects of these bright galaxies with neighbour objects. In order to avoid projection effects, we compute photometric redshifts for galaxies within 3 h ?1 Mpc in projection of LRGs and calculate the relative angle between the LRG major axis and the direction to neighbours within 1000 km s?1. We find a clear signal of alignment between LRG orientations and the distribution of galaxies within 1.5 h ?1 Mpc. The alignment effects are present only for the red population of tracers; LRG orientation is uncorrelated to the blue population of neighbour galaxies. These results add evidence to the alignment effects between primaries and satellites detected at low redshifts. We conclude that such alignments were already present at z ～ 0.5. |
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| Keywords: | galaxies: formation cosmology: theory |
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