The properties of the Malin 1 galaxy giant disk

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.

First spectroscopic study of ionised gas emission lines in the extreme low surface brightness galaxy Malin 1

“…6), consistent with the observation from Barth (2007). We have also verified that a comparison with the specific SFR radial profile (using the stellar pro-file in Boissier et al 2016) leads to the same conclusion. A similar work on two GLSB galaxies Malin 2 and UGC 6614 from Yoachim et al (in prep., private communication) also shows that GLSB galaxies in general behave like large early type galaxies at their center.…”

“…We measured a radial profile of the g-i color from the NGVS images of Malin 1 using the ellipse task in IRAF. Our measured values, computed at the NGVS resolution of ∼1 , are in good agreement with the g-i color of Malin 1 from Boissier et al (2016) computed at the GALEX resolution of 5 . Therefore, we use our measured g-i color profile to obtain a M /L i profile of Malin 1 using the empirical relation given in equation 4.…”

A multiwavelength survey of HI-excess galaxies with surprisingly inefficient star formation

“…AGC 192040 has the most prominent disk among the sample in terms of its large logM HI /M = 0.222 gas fraction, and 65 kpc H I radius (70" at z=0.047517). This galaxy is comparable to a Malin 1-type low-surface brightness galaxy in terms of its gas richness (Pickering et al 1997;Lelli, Fraternali, & Sancisi 2010;Boissier et al 2016). AGC 192040 is less extreme than Malin 1 (which has a disk size of 130 kpc radius and H I content of logM HI (M ) = 10.82), but it could be a similar type of object at slightly lower redshift (Malin 1 is at z=0.08).…”

“…A classic example of this is Malin 1 (Pickering et al 1997;Lelli, Fraternali, & Sancisi 2010). The specific angular momentum of this galaxy is ∼20 times larger than that of the Milky Way (Boissier et al 2016), spreading its 10 10.82 M of H I gas into an extended, 130 kpc radius disk. There are indications that angular momentum plays an important role in galaxies that are H I-rich for their stellar content (mass, luminosity, see Huang et al 2014;Lemonias et al 2014;Lutz et al 2017).…”

UGC 1378 – a Milky Way sized galaxy embedded in a giant low surface brightness disc

“…Our deep imaging reveals the complex E-mail:saburovaann@gmail.com structure of UGC 1378, including a high-surface brightness (HSB) bulge and disc, and a gLSB disc. In common with other gLS-BGs, UGC 1378 has prominent spiral arms (like Malin 1, Malin 2, UGC 1922, UGC 1382, Boissier et al 2016Galaz et al 2015;Hagen et al 2016;Kasparova et al 2014;Saburova 2018), resembling the Milky Way immersed in a gLSB disc.…”