Clumpy galaxies do not look like local galaxies even when the local galaxies are modified to appear as they would at high redshift. FUV images of local galaxies contain too many star-forming clumps, and they are also more centrally concentrated than clump clusters. Spiral and barred structure in local galaxies would still show up at high redshift too (using the HST ACS camera, for example), if the disk is not too faint to see.
UDF clump clusters have bigger and fewer clumps than local galaxies, even in the restframe uv, they have no symmetry or central concentration, and they are much brighter in restframe magnitudes. Typical clump clusters have surface brightnesses that are more than 10 times larger than the surface brightness of, for example, M101, which is a locally bright galaxy with lots of giant star-formation clumps (although the M101 clumps are still small by high redshift standards).
We may wonder if local flocculent spiral galaxies are a better match to high-z galaxies because local flocculents get most of their structure from gravitational instabilities in the gas and there are no prominent spiral waves in the old stellar disk. Two redshifted versions of the flocculent galaxy NGC 7793 were shown in Elmegreen et al. (2009b) and compared to GEMS galaxies. The local and distant galaxies do not look similar at all. In general, local galaxies are too smooth and too centrally concentrated compared to clump clusters.
On the other hand, a local dwarf Irregular galaxy is a good match to a
clump cluster, although the clump clusters are much more massive
(Elmegreen et
al. 2009b).
Clump clusters resemble local dwarf irregulars because
both have high gas fractions, both have big complexes relative to the
galaxy size, both have relatively thick disks, and both have high
velocity dispersions relative to the rotation speed. Recall that
LJeans / Galaxy Size ~
Hdisk / Galaxy Size ~
(
/
V)2. That is, the clump size from gravitational
instabilities is comparable to the galactic scale height, and the ratio
of these lengths to the galaxy size is the square of the ratio of the
velocity dispersion to the rotation speed. Thus big complexes, thick
disks, and high dispersions (relative to galaxy size and rotation
speed) all go together regardless of the galaxy mass.
Both local dwarf irregulars and clump clusters are irregular because
they have a relatively high gas mass and a high
/ V. Both are
also relatively young in terms of the number of rotations they have
lived and in terms of the relative gas abundance. The resemblance
between clump clusters and local dwarfs is another example of down
sizing: small galaxies today (dwarf irregulars) are doing what big
galaxies (clump clusters) did at z ~ 2
(Elmegreen et
al. 2009b).
There are other local galaxies that resemble clump clusters too, but
they have about the same stellar mass as clump clusters, i.e., they are
large galaxies. These local analogues are extremely rare, however.
Casini & Heidmann
(1976a,
1976b)
and
Maehara et
al. (1988)
discovered local
"clumpy irregular galaxies" of normal size. Examples are
Markarian 296, 325, 7, 8 (which are ultraviolet galaxies), and Kiso UV
excess galaxies 1618+378, 1624+404, 1626+413, and Mrk 297.
Maehara et
al. (1988)
determined galactic distances of 60 to 120 Mpc, clump sizes of
~ 2" (corresponding to 1 kpc), and clump absolute
magnitudes of MB ~ -11 to -16 mag (corresponding to
~ 106
L
to
108
L).
Garland et
al. (2007)
studied "Luminous Compact Blue Galaxies." These are
small, high luminosity, high surface brightness galaxies with a blue
color. They are also gas-rich (CO, HI), like high-z galaxies, and
rotating with distorted velocities, as if they are interacting or
lopsided. Overzier et al.
(2008,
2009,
2010)
studied Lyman Break Analogs
(Heckman 2005).
These are super-compact uv-luminous
galaxies. They are GALEX objects with LFUV >
1010.3
L
and intensities IFUV > 109
L
kpc-2 at redshifts z < 0.3. They are also very rare
( ~ 10-6 Mpc-3).