Clustering of the AKARI NEP deep field 24μm selected galaxies

Solarz, A.; Pollo, A.; Takeuchi, T. T.; Małek, K.; Matsuhara, H.; White, G. J.; Pȩpiak, A.; Goto, T.; Wada, T.; Oyabu, S.; Takagi, T.; Ohyama, Y.; Pearson, C. P.; Hanami, H.; Ishigaki, T. and Malkan, M. (2015). Clustering of the AKARI NEP deep field 24μm selected galaxies. Astronomy & Astrophysics, 582 A58.



Aims. We present a method of selection of 24 μm galaxies from the AKARI north ecliptic pole (NEP) deep field down to 150 μJy and measurements of their two-point correlation function. We aim to associate various 24 μm selected galaxy populations with present day galaxies and to investigate the impact of their environment on the direction of their subsequent evolution.

Methods. We discuss using of Support Vector Machines (SVM) algorithm applied to infrared photometric data to perform star-galaxy separation, in which we achieve an accuracy higher than 80%. The photometric redshift information, obtained through the CIGALE code, is used to explore the redshift dependence of the correlation function parameter (r0) as well as the linear bias evolution. This parameter relates galaxy distribution to the one of the underlying dark matter. We connect the investigated sources to their potential local descendants through a simplified model of the clustering evolution without interactions.

Results. We observe two different populations of star-forming galaxies, at zmed ∼ 0.25, zmed ∼ 0.9. Measurements of total infrared luminosities (LTIR) show that the sample at zmed ∼ 0.25 is composed mostly of local star-forming galaxies, while the sample at zmed ∼ 0.9 is composed of luminous infrared galaxies (LIRGs) with LTIR ∼ 1011.62 L. We find that dark halo mass is not necessarily correlated with the LTIR: for subsamples with LTIR = 1011.15 L at zmed ∼ 0.7 we observe a higher clustering length (r0 = 6.21 ± 0.78 [h−1Mpc]) than for a subsample with mean LTIR = 1011.84 L at zmed ∼ 1.1 (r0 = 5.86 ± 0.69 h−1Mpc). We find that galaxies at zmed ∼ 0.9 can be ancestors of present day L early type galaxies, which exhibit a very high r0 ∼ 8h−1 Mpc.

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