More evidence for hidden spiral and bar features in bright early-type dwarf galaxies

Abstract

Abstract. Following the discovery of spiral structure in IC 3328 (Jerjen et al. 2000), we present further evidence that a sizable fraction of bright early-type dwarfs in the Virgo cluster are genuine disk galaxies, or are hosting a disk component. Among a sample of 23 nucleated dwarf ellipticals and dS0s observed with the Very Large Telescope in B and R, we found another four systems exhibiting non-axisymmetric structures, such as a bar and/or spiral arms, indicative of a disk (IC 0783, IC 3349, NGC 4431, IC 3468). Particularly remarkable are the two-armed spiral pattern in IC 0783 and the bar and trailing arms in NGC 4431. For both galaxies the disk nature has recently been confirmed by a rotation velocity measurement (Simien & Prugniel 2002). Our photometric search is based on a Fourier decomposition method and a specific version of unsharp masking. Some "early-type" dwarfs in the Virgo cluster seem to be former late-type galaxies which were transformed to early-type morphology, e.g. by "harassment", during their infall to the cluster, while maintaining part of their disk structure.

Embedded disks in Fornax dwarf elliptical galaxies

“…This galaxy possesses a large bulge. These results can be compared to the findings of Jerjen et al (2000) and Barazza et al (2002) who discovered nucleated dEs with spiral and bar features in the Virgo Cluster. …”

“…We smoothed the R-band image of a galaxy with the MIDAS command filter/med 1 , which replaces each pixel by the median of a surrounding box. Like Barazza et al (2002), we opted for a 6 × 6 box. This smoothed image is then subtracted off the original one, highlighting any fine structure.…”

“…De Rijcke, et al (2001) and Simien & Prugniel (2002). Jerjen et al (2000) and Barazza et al (2002) discovered spiral structure and bars in 5 bright nucleated dEs in the Virgo Cluster: IC 3328, IC 0783, IC 3349, NGC 4431, and IC 3468. Ryden et al (1999) also report dEs with disky isophotes in the Virgo cluster.…”

The Next Generation Virgo Cluster Survey Xvi: The Angular Momentum of Dwarf Early-Type Galaxies From Globular Cluster Satellites

“…This makes the morphological classification strongly dependent on the data quality, depth, and resolution. Therefore, it is not surprising that, as better data becomes available, many galaxies formerly classified as dEs show a substantial amount of substructure in the form of spiral arms, disks, and/or irregular features (Jerjen et al 2000;Barazza et al 2002;De Rijcke et al 2003;Geha et al 2003;Graham & Guzmán 2003;Ferrarese et al 2006;Lisker et al 2006aLisker et al , 2006bLisker et al , 2007Janz et al 2012Janz et al , 2014.…”

Detailed kinematics and morphological features in tidally heated disks

“…Recent observations confirm that early type galaxies have a broad range of photometric and kinematical characteristics. Jerjen, Kalnajs & Binggeli (2000) and Barazza, Binggeli & Jerjen (2002) discovered hidden spiral structures and bar features in bright dEs in the Virgo cluster. Spirals and disks were also observed within dwarf spheroidal galaxies in the Coma (Graham, Jerjen &Guzmán 2003 andFornax clusters (De Rijcke et al 2001).…”