期刊
ASTROPHYSICAL JOURNAL
卷 777, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/777/2/155
关键词
galaxies: evolution; galaxies: formation; galaxies: high-redshift; galaxies: structure
资金
- Japan Society for the Promotion of Science (JSPS)
- KAKENHI [24840010, 23244025]
- World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan
- UK Science and Technology Facilities Council
- Space Telescope Science Institute [HST-GO-12498.01]
- European Research Council via the award of an Advanced Grant
- Royal Society through a Wolfson Research Merit Award
- European Commission
- NASA [NAS5-26555]
- Science and Technology Facilities Council [ST/J001422/1] Funding Source: researchfish
- STFC [ST/J001422/1] Funding Source: UKRI
- Grants-in-Aid for Scientific Research [23244022, 24840010, 23244025] Funding Source: KAKEN
We analyze the redshift-and luminosity-dependent sizes of dropout galaxy candidates in the redshift range z similar to 7-12 using deep images from the 2012 Hubble Ultra Deep Field (UDF12) campaign, which offers two advantages over that used in earlier work. First, we utilize the increased signal-to-noise ratio offered by the UDF12 imaging to provide improved measurements for known galaxies at z similar or equal to 6.5-8 in the HUDF. Second, because the UDF12 data have allowed the construction of the first robust galaxy sample in the HUDF at z > 8, we have been able to extend the measurement of average galaxy size out to higher redshifts. Restricting our measurements to sources detected at > 15s, we confirm earlier indications that the average half-light radii of z similar to 7-12 galaxies are extremely small, 0.3-0.4 kpc, comparable to the sizes of giant molecular associations in local star-forming galaxies. We also confirm that there is a clear trend of decreasing half-light radius with increasing redshift, and provide the first evidence that this trend continues beyond z similar or equal to 8. Modeling the evolution of the average half-light radius as a power law,.(1 + z) s, we obtain a best-fit index of s = -1.30(-0.14)(+0.12) over z similar to 4-12. A clear size-luminosity relation is evident in our dropout samples. This relation can be interpreted in terms of a constant surface density of star formation over a range in luminosity of 0.05-1.0L* z = 3. The average star formation surface density in dropout galaxies is 2-3 orders of magnitude lower than that found in extreme starburst galaxies, but is comparable to that seen today in the centers of normal disk galaxies.
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