Clustering of the AKARI NEP deep field 24 μm selected galaxies

¹ Division of Particle and Astrophysical ScienceNagoya University, Furo-cho, Chikusa-ku, 464-8602 Nagoya, Japan
e-mail: aleksandra.solarz@ncbj.gov.pl
² National Center for Nuclear Research, ul. Hoża 69, 00-681 Warsaw, Poland
³ The Astronomical Observatory of the Jagiellonian University, ul. Orla 171, 30-244 Kraków, Poland
⁴ Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, 252-5210 Kanagawa, Japan
⁵ Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
⁶ Space Science and Technology Department, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK
⁷ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
⁸ National Astronomical Observatory, 2-21-1 Osawa, Mitaka, 181-8588 Tokyo, Japan
⁹ Academia Sinica, Institute of Astronomy and Astrophysics, 10617 Taipei, Taiwan
¹⁰ Department of Physics, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1J 1B1, Canada
¹¹ Physics Section, Faculty of Humanities and Social Sciences, Iwate University, 020-8550 Morioka, Japan
¹² Departament of Physics and Astronomy, University of California, Los Angeles, CA 90024, USA

Received: 4 January 2014
Accepted: 4 August 2015

Abstract

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 z_med ~ 0.25, z_med ~ 0.9. Measurements of total infrared luminosities (L_TIR) show that the sample at z_med ~ 0.25 is composed mostly of local star-forming galaxies, while the sample at z_med ~ 0.9 is composed of luminous infrared galaxies (LIRGs) with L_TIR ~ 10^11.62 L_⊙. We find that dark halo mass is not necessarily correlated with the L_TIR: for subsamples with L_TIR = 10^11.15 L_⊙ at z_med ~ 0.7 we observe a higher clustering length (r₀ = 6.21 ± 0.78[ h^-1Mpc ]) than for a subsample with mean L_TIR = 10^11.84 L_⊙ at z_med ~ 1.1 (r₀ = 5.86 ± 0.69h^-1Mpc). We find that galaxies at z_med ~ 0.9 can be ancestors of present day L_∗ early type galaxies, which exhibit a very high r₀ ~ 8h^-1 Mpc.