J/A+A/681/A15ivo://CDS.VizieR/J/A+A/681/A15doi:10.26093/cds/vizier.36810015CDSMontes M.Trujillo I.Karunakaran A.Infante-Sainz R.Spekkens K.,Golini G.Beasley M.Cebrian M.Chamba N.D'Onofrio M.Kelvin L.,Roman J.2024-11-06T20:06:39Z2024-01-09T08:29:10ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgalaxiesvisible-astronomysloan-photometryAlmost Dark Galaxies are objects that have eluded detection by traditional surveys such as the Sloan Digital Sky Survey (SDSS). The low surface brightness of these galaxies ({mu}r(0)>26mag/arcsec^2^), and hence their low surface stellar mass density (a few solar masses per pc^2^ or less), suggests that the energy density released by baryonic feedback mechanisms is inefficient in modifying the distribution of the dark matter halos they inhabit. For this reason, almost dark galaxies are particularly promising for probing the microphysical nature of dark matter. In this paper, we present the serendipitous discovery of Nube, an almost dark galaxy with <{mu}V>_e_~26.7mag/arcsec^2^. The galaxy was identified using deep optical imaging from the IAC Stripe82 Legacy Project. Follow-up observations with the 100m Green Bank Telescope strongly suggest that the galaxy is at a distance of 107Mpc. Ultra-deep multi-band observations with the 10.4m Gran Telescopio Canarias favour an age of ~10Gyr and a metallicity of [Fe/H]~-1.1. With a stellar mass of ~4x10^8^M_{sun}) and a half-mass radius of Re=6.9kpc (corresponding to an effective surface density of <{SIGMA}>_e_~0.9 M_{sun}_/pc^2^), Nube is the most massive and extended object of its kind discovered so far. The galaxy is ten times fainter and has an effective radius three times larger than typical ultra-diffuse galaxies with similar stellar masses. Galaxies with comparable effective surface brightness within the Local Group have very low mass (tens of 10^5^M_{sun}_) and compact structures (effective radius Re<1kpc). Current cosmological simulations within the cold dark matter scenario, including baryonic feedback, do not reproduce the structural properties of Nube. However, its highly extended and flattened structure is consistent with a scenario where the dark matter particles are ultra-light axions with a mass of mB=(0.8^+0.4^_-0.2_)x10^-23^eV.2024A&A...681A..15Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/681/A15CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/681/A15https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/681/A15http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/681/A15https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/681/A15https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/681/A15http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/681/A15GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/681/A15/list (List of fits images)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/681/A15/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/681/A15/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/681/A15/list?GETtext/xml+votable180.050000true20.86715-0.612260.0055555555555555566/18004https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/681/A15?format=asciiOpticaldefaultJ/A+A/681/A15/listList of fits imagesFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitscharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintsizeSize of FITS fileKibytephys.size;meta.fitsint