arXiv subjects

Chian-Chou Chen

Publications and source records attributed to Chian-Chou Chen.

110 records · Page 7Linked to original sources

arXiv2011

Faint Submillimeter Galaxies behind the Massive Lensing Cluster A2390

Current studies on Submillimeter Galaxies (SMGs) mostly focus on bright sources with 850 micron flux greater than 2 mJy, and the results have shown that they are likely high redshift mergers with z > 2 and could be a dominant population on star formation in the early Universe. However, bright SMGs only contributes 20-30% of the 850 micron extragalactic background light (EBL), meaning the bulk of the cosmic star formation still hidden by dust and our current understanding is biased. We have started a program to study an unbiased sample of highly-amplified and intrinsically faint SCUBA detected SMGs in the field of massive lensing clusters. Here we report the newly obtained SMA observations at 850 micron on one of our sample source, A2390-5, behind the massive lensing cluster A2390. We successfully detect the source with a flux of 3.95 mJy. Surprisingly, it does not have any counterpart in any other wavelengths even though there are tentative candidates, which implies a very dusty and high-z nature. With less than 1" positional accuracy and the adoption of z = 5, we obtain the amplification factor of 12 using current lensing model, which makes A2390-5 a faint SMG with a de-lensed flux of 0.33 mJy. Together with our previous detection on another faint SMG, both of them have no counterpart in other wavelengths and their properties are very different than previously thought from the single-dish data. We emphasize the importance of direct submillimeter high-resolution studies on faint SMGs, which could be the dominant population of the high-z star formation.

astro-ph.CO↗

arXiv2011

Submillimeter sources behind the massive lensing clusters A370 and A2390

We report 850 micron Submillimeter Array (SMA) observations of four gravitationally lensed submillimeter galaxies (SMGs), A370-2, A2390-1, A2390-3 and A2390-4, which were originally discovered with the Submillimeter Common-User Bolometer Array (SCUBA). Our SMA detection of A370-2 with a submillimeter flux of 7.95 +/- 0.60 mJy unambiguously identifies the counterparts to this source at optical and radio wavelengths. A2390-1 is an ultraluminous infrared galaxies with a submillimeter flux of 5.55 +/- 0.92 mJy and a redshift of 1.8 +/- 0.2 computed from submillimeter/radio flux ratio analysis. We resolve A2390-3 into two components, A2390-3a and A2390-3b, with fluxes of 3.15 +/- 0.63 mJy and 1.92 +/- 0.60 mJy, respectively. The structure of the system could be consistent with morphological distortion by gravitational lensing. The lack of counterparts in the optical and infrared indicates a heavily dust-enshrouded nature, and a non-detection in the radio implies that these two sources probably lie at z > 4.7, which would make them among the most distant SMGs known to date. Our non-detection of A2390-4 suggests either that there are multiple fainter submillimeter sources within the SCUBA beam or that the SCUBA detection may have been false. Our precise positions allow us to determine accurate amplifications and fluxes for all our detected sources. Our new results give a shallower power-law fit (-1.10) to the faint-end 850 micron cumulative number counts than previous work. We emphasize the need for high-resolution observations of single-dish detected SMGs in order to measure accurately the faint end of the 850 micron counts.

astro-ph.CO↗