DGSAT: Dwarf Galaxy Survey with Amateur Telescopes

Abstract

Context. We introduce the Dwarf Galaxy Survey with Amateur Telescopes (DGSAT) project and report the discovery of eleven low surface brightness (LSB) galaxies in the fields of the nearby galaxies NGC 2683, NGC 3628, NGC 4594 (M 104), NGC 4631, NGC 5457 (M 101), and NGC 7814. Aims. The DGSAT project aims to use the potential of small-sized telescopes to probe LSB features around large galaxies and to increase the sample size of the dwarf satellite galaxies in the Local Volume. Methods. Using long exposure images, fields of the target spiral galaxies are explored for extended LSB objects. After identifying dwarf galaxy candidates, their observed properties are extracted by fitting models to their light profiles. Results. We find three, one, three, one, one, and two new LSB galaxies in the fields of NGC 2683, 3628, 4594, 4631, 5457, and 7814, respectively. In addition to the newly found galaxies, we analyse the structural properties of nine already known galaxies. All of these 20 dwarf galaxy candidates have effective surface brightnesses in the range 25.3 < ∼ µ e < ∼ 28.8 mag arcsec −2 and are fit with Sersic profiles with indices n < ∼ 1. Assuming that they are in the vicinity of the above mentioned massive galaxies, their r-band absolute magnitudes, their effective radii, and their luminosities are in the ranges −15.6 < ∼ M r < ∼ −7.8, 160 pc < ∼ R e < ∼ 4.1 kpc, and 0.1 × 10 6 < ∼ L L r < ∼ 127 × 10 6 , respectively. To determine whether these LSB galaxies are indeed satellites of the above mentioned massive galaxies, their distances need to be determined via further observations. Conclusions. Using small telescopes, we are readily able to detect LSB galaxies with similar properties to the known dwarf galaxies of the Local Group.

Resolved Stellar Streams around NGC 4631 from a Subaru/Hyper Suprime-Cam Survey

“…Therefore, these control fields are located at almost the same projected vertical distance from NGC 4631's disk as the stream fields, and does not have any remarkable substructures of high S/N within these fields. The four orange circles present the candidates of dwarf galaxies reported by the previous studies (Seth et al 2005a;Karachentsev et al 2014;Martínez-Delgado et al 2015;Javanmardi et al 2016). The eight blue ones show candidate new dwarf galaxies identified through the visual inspection in this study (see Section 3.1).…”

“…The column of Stellar Population shows which in RGB/AGB/RSG/MS maps each candidate is detected. HSC-1 and HSC-11 are unresolved in our HSC image, while HSC-3, which was previously-reported as a low surface brightness galaxy by a small amateur telescope (Javanmardi et al 2016), is apparently a blending object in our HSC image. † (1) Seth et al (2005a), (2) Figure 3.…”

“…This is because integrated surface brightness is independent of distance. Subsequently, other groups inspired by Martínez-Delgado et al (2010) have adopted this observational methodology to perform a direct test of the ΛCDM cosmology (e.g., van Dokkum et al 2014;Javanmardi et al 2016;Merritt et al 2016). These authors also found the varieties in the stellar halos in more distant nearby spiral galaxies beyond the Local Volume, implying stochasticity in the accretion histories of galax-ies.…”

DGSAT: Dwarf Galaxy Survey with Amateur Telescopes

“…A characteristic r e = 500 pc (e.g. Javanmardi et al 2016) corresponds to 3 at a distance of 30 Mpc (≈2000 km s −1 recessional velocity; see also fig. 5 of Carrasco et al 2006)).…”

“…Merrit et al 2014;Javanmardi et al 2016), the field of view of optical telescopes is another important parameter. It should allow for direct imaging of the entire relevant volume surrounding a host galaxy.…”