The orientation of galaxy pairs with filamentary structures: dependence on morphology

VALERIA MESA; FERNANDA DUPLANCIC; MA. SOL ALONSO; MUÑOZ MARÍA ROSA; COLDWELL, GEORGINA V; DIEGO GARCÍA LAMBAS

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2018 vol. 619

0004-6361

Aims. With the aim of performing an analysis of the orientations of galaxypair systems with respect to the underlying large-scale structure, we study thealignment between the axis connecting the pair galaxies and the host cosmicfilament where the pair resides. In addition, we analyze the dependence of theamplitude of the alignment on the morphology of pair members as well asfilament properties. Methods. We build a galaxy pair catalog requiring $r_p < 100kpc$ and $Delta V < 500 kms$ within redshift z<0.1 from the SloanDigital Sky Survey (SDSS). We divided the galaxy pair catalog taking intoaccount the morphological classification by defining three pair categoriescomposed by elliptical-elliptical (E-E), elliptical-spiral (E-S) andspiral-spiral (S-S) galaxies. We use a previously defined catalog of filamentsobtained from SDSS and we select pairs located closer than $1mpc$ from thefilament spine, which are considered as members of filaments. For these pairs,we calculate the relative angle between the axis connecting each galaxy, andthe direction defined by the spine of the parent filament.Results. We find a statistically significant alignment signal between thepair axes and the spine of the host filaments consistent with a relative excessof ∼ 15% aligned pairs. We obtain that pairs composed by ellipticalgalaxies exhibit a stronger alignment, showing a higher alignment signal forpairs closer than 200 $kpc$ to the filament spine. In addition, we find thatthe aligned pairs are associated with luminous host filaments populated with ahigh fraction of elliptical galaxies.The findings of this work show that large scale structures play a fundamentalrole in driving galactic anisotropic accretion as induced by galaxy pairsexhibiting a preferred alignment along the filament direction.