arXiv subjects

Javier Román

Publications and source records attributed to Javier Román.

40 records · Page 3Linked to original sources

arXiv2018

The IAC Stripe82 Legacy Survey: improved sky-rectified images

The IAC Stripe 82 Legacy Survey is a new co-addition of the SDSS Stripe 82 data (Abazajian et al. 2009), especially reduced to preserve the faintest surface brightness features of this data set. The survey maps a 2.5 degree wide stripe along the Celestial Equator in the Southern Galactic Cap (-50$^{\circ}$ $<$ R.A. $<$ 60$^{\circ}$, -1.25$^{\circ}$ $<$ Dec.$<$ 1.25$^{\circ}$) with a total of 275 square degrees in all the five SDSS filters (u,g,r,i,z). The new reduction includes an additional and deeper band (rdeep), which is a combination of g, r and i bands. The average seeing of the Stripe82 dataset is around 1 arcsec. The mean surface brightness limits are $μ_{lim}$[3$σ$,10$\times$10 arcsec$^{2}$] = 27.9, 29.1, 28.6, 28.1 and 26.7 mag arcsec$^{-2}$ for the u, g, r, i and z bands respectively. The significant depth of the data and the emphasis on preserving the characteristics of the background (sky + diffuse light) through a non-aggressive sky subtraction strategy make this dataset suitable for the study of the low surface brightness Universe. In this research note we present a new data release with improved sky-rectified images. This new data-set is published on the survey webpage and is publicly available for the community.

astro-ph.GA↗

arXiv2017

Ultra diffuse galaxies outside clusters: clues to their formation and evolution

We identify six ultra diffuse galaxies (UDGs) outside clusters in three nearby isolated groups (z<0.026) using very deep imaging in three different SDSS filters (g, r and i bands) from the IAC Stripe82 Legacy Project. By comparing with the abundance of UDGs in rich galaxy clusters, we find that the density of UDGs (i.e. their number per unit mass of the host structure where they are located) decreases towards the most massive systems. This is compatible with a scenario where UDGs are formed preferentially outside clusters. In the periphery (D>250 kpc) of our three groups, we identify a population of potential UDG progenitors (two of them confirmed spectroscopically). These progenitors have similar masses, shapes and sizes but are bluer, g-i~0.45, (and for this reason brighter, mu_g(0)<24 mag arcsec -2) than traditional UDGs (g-i~0.76). A passive evolution of these progenitors will transform them into regular (i.e. mu_g(0)>24 mag arcsec -2) UDGs after ~6 Gyr. If confirmed, our observations support a scenario where UDGs are old, extended, low surface brightness dwarfs (M*~10^8 Msun) galaxies born in the field, are later on processed in groups and, ultimately, infall into galaxy clusters by group accretion.

astro-ph.GA↗

arXiv2017

Spatial distribution of ultra-diffuse galaxies within large-scale structures

Taking advantage of the Sloan Digital Sky Survey Stripe82 data, we have explored the spatial distribution of ultra-diffuse galaxies (UDGs) within an area of 8$\times$8 Mpc$^2$ centred around the galaxy cluster Abell 168 ($z$ = 0.045). This intermediate massive cluster ($σ$ = 550 km s$^{-1}$) is surrounded by a complex large-scale structure. Our work confirms the presence of UDGs in the cluster and in the large-scale structure that surrounds it, and it is the first detection of UDGs outside clusters. Approximately 50 per cent of the UDGs analysed in the selected area inhabit the cluster region ($\sim$11 $\pm$ 5 per cent in the core and $\sim$39 $\pm$ 9 per cent in the outskirts), whereas the remaining UDGs are found outside the main cluster structure ($\sim$50 $\pm$ 11 per cent). The colours and the spatial distribution of the UDGs within this large-scale structure are more similar to the dwarf galaxies than to L$_\star$ galaxies, suggesting that most of UDGs could be bona fide dwarf galaxies.

astro-ph.GA↗

arXiv2017

The nearest ultra diffuse galaxy: UGC2162

We describe the structural, stellar population and gas properties of the nearest Ultra Diffuse Galaxy (UDG) discovered so far: UGC2162 (z=0.00392; R$_{e,g}$=1.7$(\pm$0.2) kpc; $μ_g(0)$=24.4$\pm$0.1 mag/arcsec$^2$; g-i=0.33$\pm$0.02). This galaxy, located at a distance of 12.3($\pm$1.7) Mpc, is a member of the M77 group. UGC2162 has a stellar mass of $\sim$2($^{+2}_{-1}$)$\times$10$^7$ M$_\odot$ and is embedded within a cloud of HI gas $\sim$10 times more massive: $\sim$1.9($\pm$0.6)$\times$10$^8$ M$_\odot$. Using the width of its HI line as a dynamical proxy, the enclosed mass within the inner R$\sim$5 kpc is $\sim$4.6($\pm$0.8)$\times$10$^9$ M$_\odot$ (i.e. M/L$\sim$200). The estimated virial mass from the cumulative mass curve is $\sim$8($\pm$2)$\times$10$^{10}$ M$_\odot$. Ultra-deep imaging from the IAC Stripe82 Legacy Project show that the galaxy is irregular and has many star forming knots, with a gas-phase metallicity around one-third of the solar value. Its estimated Star Formation Rate (SFR) is $\sim$0.01 M$_\odot$/yr. This SFR would double the stellar mass of the object in $\sim$2 Gyr. If the object were to stop forming stars at this moment, after a passive evolution, its surface brightness would become extremely faint: $μ_g(0)$$\sim$27 mag/arcsec$^2$ and its size would remain large R$_{e,g}$$\sim$ 1.8 kpc. Such faintness would make it almost undetectable to most present-day surveys. This suggests that there could be an important population of M$_{\star}$$\sim$10$^7$ M$_\odot$ "dark galaxies" in rich environments (depleted of HI gas) waiting to be discovered by current and future ultra-deep surveys.

astro-ph.GA↗