Bibcode
Hinojosa-Goñi, R.; Muñoz-Tuñón, C.; Méndez-Abreu, J.
Bibliographical reference
Astronomy and Astrophysics, Volume 592, id.A122, 17 pp.
Advertised on:
8
2016
Journal
Citations
22
Refereed citations
20
Description
Context. At high redshift, starburst galaxies present irregular
morphologies with 10-20% of their star formation occurring in giant
clumps. These clumpy galaxies are considered the progenitors of local
disk galaxies. To understand the properties of starbursts at
intermediate and low redshift, it is fundamental to track their
evolution and the possible link with the systems at higher z.
Aims: We present an extensive, systematic, and multiband search and
analysis of the starburst galaxies at redshift (0 < z < 0.5) in
the COSMOS field, as well as detailed characteristics of their
star-forming clumps by using Hubble Space Telescope/Advance Camera for
Surveys (HST/ACS) images. Methods: The starburst galaxies are
identified using a tailor-made intermediate-band color excess selection,
tracing the simultaneous presence of Hα and [OIII] emission lines
in the galaxies. Our methodology uses previous information from the
zCOSMOS spectral database to calibrate the color excess as a function of
the equivalent width of both spectral lines. This technique allows us to
identify 220 starburst galaxies at redshift 0 < z < 0.5 using the
SUBARU intermediate-band filters. Combining the high spatial resolution
images from the HST/ACS with ground-based multi-wavelength photometry,
we identify and parametrize the star-forming clumps in every galaxy.
Their principal properties, sizes, masses, and star formation rates are
provided. Results: The mass distribution of the starburst
galaxies is remarkably similar to that of the whole galaxy sample with a
peak around M/M⊙ ~ 2 × 108 and only a
few galaxies with M/M⊙ > 1010. We classify
galaxies into three main types, depending on their HST morphology:
single knot (Sknot), single star-forming knot plus diffuse light
(Sknot+diffuse), and multiple star-forming knots (Mknots/clumpy) galaxy.
We found a fraction of Mknots/clumpy galaxy fclumpy = 0.24
considering out total sample of starburst galaxies up to z ~ 0.5. The
individual star-forming knots in our sample follows the same L(Hα)
vs. size scaling relation as local giant HII regions. However, they
slightly differ from the one provided using samples at high redshift.
This result highlights the importance of spatially resolving the
star-forming regions for this kind of study. Star-forming clumps in the
central regions of Mknots galaxies are more massive, and present higher
star formation rates, than those in the outskirts. This trend is less
clear when we consider either the mass surface density or surface star
formation rate. Sknot galaxies do show properties similar to both dwarf
elliptical and irregulars in the surface brightness (μ) versus
Mhost diagram in the B-band, and to spheroidals and
ellipticals in the μ versus Mhost diagram in the V-band.
Conclusions: The properties of our star-forming knots in
Sknot+diffuse and Mknots/clumpy galaxies support the predictions of
recent numerical simulations claiming that they have been produced by
violent disk instabilities. We suggest that the evolution of these knots
means that large and massive clumps at the galaxy centers represent the
end product of the coalescence of surviving smaller clumps from the
outskirts. Our results support this mechanism and make it unlikely that
mergers are the reason behind the observed starburst knots. Sknot
galaxies might be transitional phases of the Blue Compact Dwarfs (BCD)
class, with their properties consistent with spheroidal-like, but blue
structures.
Tables 3 and 4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A122