Our understanding of SFDGs has drastically improved in recent years
thanks to data from space telescopes and large groundbased optical,
near-IR and radio telescopes. In particular the data from HST, GALEX and
21-cm surveys have improved our understanding of the formation and
evolution of SFDGs and their relation to other galaxy types. The ACS
nearby galaxy survey (ANGST;
Dalcanton
et al. 2009)
uses data from
HST to derive CMDs and detailed SF histories. The survey contains 69
galaxies of which 58% are dIs, 17% spirals and the rest dEs. The 11
Mpc H
and Ultraviolet
Galaxy Survey (11HUGS;
Lee et
al. 2004)
uses H and GALEX images
to look at the SF
properties of SFDGs in the local volume out to 11 Mpc. Both these
surveys also use Spitzer data. A dedicated Spitzer programme, the
Spitzer Local Volume Legacy Syrvey (LVL) has observed 258 nearby
galaxies, many of which are supplemented by groundbased images in
broadbands and H. The
Faint Irregular Galaxies (65 dIs) GMRT Survey (FIGGS;
Begum
et al. 2008),
is using the Giant Metrewave Radio
Telescope (GMRT) to perform volume limited (< 10 Mpc) H I observations
of SFDGs. The H I Nearby Galaxy Survey (THINGS;
Walter
et al. 2008),
at the VLA, includes 34 galaxies, of which
about a dozen are SFDGs, in the distance interval 3 < D < 15 Mpc. The
resolution is 7" and 5 kms-1. A similar study, 'Little
Things', concerns VLA observations of 41 dIs. Finally, the Arecibo
Legacy Fast ALFA (ALFALFA) blind extragalactic H I survey
(Giovanelli et al. 2005)
will survey galaxies at high latitudes out to a radial velocity of 18000
km s-1. It will improve dramatically on the predecessor HI
Parkes All-Sky Survey (HIPASS;
Barnes
et al. 2001).
As part of the results the survey will provide us with data of hundreds
of dwarf galaxies with H I masses < 107.5
M
.