The properties of the Malin 1 galaxy giant disk

A panchromatic view from the NGVS and GUViCS surveys^⋆

¹ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
e-mail: samuel.boissier@lam.fr
² National Research Council of Canada, Herzberg Astronomy and Astrophysics Program, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada
³ CEA/IRFU/SAp, Laboratoire AIM Paris-Saclay, CNRS/INSU, Université Paris Diderot, Observatoire de Paris, PSL Research University, CEA/IRFU/SAp, Laboratoire AIM Paris-Saclay, CNRS/INSU, Université Paris Diderot, Observatoire de Paris, PSL Research University, 91191 Gif-sur-Yvette Cedex, France
⁴ Department of Physics, Engineering Physics & Astronomy, Queen’s University, Kingston, Ontario, Canada
⁵ NAOJ Chile Observatory, National Astronomical Observatory of Japan, Joaquin Montero 3000 Oficina 702, Vitacura, 763-0409 Santiago, Chile
⁶ Joint ALMA Office, Alonso de Cordova 3107, Vitacura, 763-0355 Santiago, Chile
⁷ Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800, USA
⁸ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago, Chile
⁹ Departamento de Astrofísica, Universidad Complutense de Madrid, 28040 Madrid, Spain
¹⁰ Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101, USA

Received: 1 July 2016
Accepted: 11 September 2016

Abstract

Context. Low surface brightness galaxies (LSBGs) represent a significant percentage of local galaxies but their formation and evolution remain elusive. They may hold crucial information for our understanding of many key issues (i.e., census of baryonic and dark matter, star formation in the low density regime, mass function). The most massive examples – the so called giant LSBGs – can be as massive as the Milky Way, but with this mass being distributed in a much larger disk.

Aims. Malin 1 is an iconic giant LSBG – perhaps the largest disk galaxy known. We attempt to bring new insights on its structure and evolution on the basis of new images covering a wide range in wavelength.

Methods. We have computed surface brightness profiles (and average surface brightnesses in 16 regions of interest), in six photometric bands (FUV, NUV, u, g, i, z). We compared these data to various models, testing a variety of assumptions concerning the formation and evolution of Malin 1.

Results. We find that the surface brightness and color profiles can be reproduced by a long and quiet star-formation history due to the low surface density; no significant event, such as a collision, is necessary. Such quiet star formation across the giant disk is obtained in a disk model calibrated for the Milky Way, but with an angular momentum approximately 20 times larger. Signs of small variations of the star-formation history are indicated by the diversity of ages found when different regions within the galaxy are intercompared.

Conclusions. For the first time, panchromatic images of Malin 1 are used to constrain the stellar populations and the history of this iconic example among giant LSBGs. Based on our model, the extreme disk of Malin 1 is found to have a long history of relatively low star formation (about 2 M_⊙ yr^-1). Our model allows us to make predictions on its stellar mass and metallicity.