Merging galaxies in isolated environments

I. Multiband photometry, classification, stellar masses, and star formation rates^★

¹ Departamento de Física, Universidad Técnica Federico Santa María, Avenida Vicuña Mackenna 3939, San Joaquín, Santiago de Chile, Chile
e-mail: pau.astro.cc@gmail.com
² Astronomy Department, Universidad de Concepción, Casilla 160-C, Concepción, Chile
³ Department of Astronomy and Yonsei University Observatory, Yonsei University, Seoul 03722, Republic of Korea
⁴ Academia Sinica Institute of Astronomy and Astrophysics, No. 1 Section 4 Roosevelt Rd., 11F of Astro-Math Building, Taipei 10617, Taiwan
⁵ Instituto de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Valparaiso, Chile
⁶ Chinese Academy of Sciences South America Center for Astronomy, China-Chile Joint Center for Astronomy, Camino El Observatorio #1515, Las Condes, Santiago, Chile
⁷ CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, PR China
⁸ School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, PR China

Received: 15 March 2018
Accepted: 2 April 2019

Abstract

Context. Extragalactic surveys provide significant statistical data for the study of crucial galaxy parameters (e.g. stellar mass, M_*, and star formation rate, SFR) used to constrain galaxy evolution under different environmental conditions. These quantities are derived using manual or automatic methods for galaxy detection and flux measurement in imaging data at different wavelengths. The reliability of these automatic measurements, however, is subject to mis-identification and poor fitting due to the morphological irregularities present in resolved nearby galaxies (e.g. clumps, tidal disturbances, star- forming regions) and its environment (galaxies in overlap).

Aims. Our aim is to provide accurate multi-wavelength photometry (from the UV to the IR, including GALEX, SDSS, and WISE) in a sample of ~600 nearby (ɀ < 0.1) isolated mergers, as well as estimations of M, and SFR.

Methods. We performed photometry following a semi-automated approach using SExtractor, confirming by visual inspection that we successfully extracted the light from the entire galaxy, including tidal tails and star-forming regions. We used the available SED fitting code MAGPHYS in order to estimate M*, and SFR.

Results. We provide the first catalogue of isolated merging galaxies of galaxy mergers including aperture-corrected photometry in 11 bands (FUV, NUV, u, 𝑔, r, i, ɀ, W1, W2, W3, and W4), morphological classification, merging stage, M_*, and SFR. We found that SFR and M_*, derived from automated catalogues can be wrong by up to three orders of magnitude as a result of incorrect photometry.

Conclusions. Contrary to previous methods, our semi-automated method can reliably extract the flux of a merging system completely. Even when the SED fitting often smooths out some of the differences in the photometry, caution using automatic photometry is suggested as these measurements can lead to large differences in M_*, and SFR estimations.