The StEllar Counterparts of COmpact high velocity clouds (SECCO) survey

II. Sensitivity of the survey and the atlas of synthetic dwarf galaxies^⋆

¹ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany
e-mail: gbeccari@eso.org
² INAF−Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
³ Instituto de Astrofsica de Canarias, 38205 La Laguna, Tenerife, Spain
⁴ Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l’Université, 67000 Strasbourg, France
⁵ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁶ INAF−Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio, Italy
⁷ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁸ Universidad de la Laguna, Dpto. Astrofisica, 38206 La Laguna, Tenerife, Spain

Received: 6 November 2015
Accepted: 10 April 2016

Abstract

The searching for StEllar Counterparts of COmpact high velocity clouds (SECCO) survey is devoted to the search for stellar counterparts within ultra compact high velocity clouds that are candidate low-mass, low-luminosity galaxies. We present the results of a set of simulations aimed at the quantitative estimate of the sensitivity of the survey as a function of the total luminosity, size, and distance of the stellar systems we are looking for. For all of our synthetic galaxies we assumed an exponential surface brightness profile and an old and metal-poor population. The synthetic galaxies are simulated both on the images and on the photometric catalogues, taking all the observational effects into account. In the fields where the available observational material is of top quality (≃36% of the SECCO fields), we detect synthetic galaxies as ≥5σ over-densities of resolved stars down to μ_V,h ≃ 30.0 mag/arcsec², for D ≤ 1.5 Mpc, and down to μ_V,h ≃ 29.5 mag/arcsec², for D ≤ 2.5 Mpc. In the field with the worst observational material of the whole survey, we detect synthetic galaxies with μ_V,h ≤ 28.8 mag/arcsec² out to D ≤ 1.0 Mpc, and those with μ_V,h ≤ 27.5 mag/arcsec² out to D ≤ 2.5 Mpc. Dwarf galaxies with M_V = −10.0, with sizes in the range spanned by known dwarfs, are detected by visual inspection of the images up to D = 5 Mpc independent of the image quality. In the best quality images, dwarfs are partially resolved into stars up to D = 3.0 Mpc and completely unresolved at D = 5 Mpc. As an independent test of the sensitivity of our images to low surface brightness galaxies, we report on the detection of several dwarf spheroidal galaxies probably located in the Virgo cluster with M_V ≲ −8.0 and μ_V,h ≲ 26.8 mag/arcsec². The nature of the previously discovered SECCO 1 stellar system, also likely located in the Virgo cluster, is rediscussed in comparison with these dwarfs. While specific for the SECCO survey, our study may also provide general guidelines for the detection of faint stellar systems with 8 m class telescopes.