An ACA Survey of [C i] <sup>3</sup> P <sub>1</sub>−<sup>3</sup> P <sub>0</sub>, CO J = 4 − 3, and Dust Continuum in Nearby U/LIRGs
Tomonari Michiyama, Toshiki Saito, Ken-ichi Tadaki, Junko Ueda, Ming-Yang Zhuang, Juan Molina, Bumhyun Lee, Ran Wang, Alberto D. Bolatto, Daisuke Iono, Kouichiro Nakanishi, Takuma Izumi, Takuji Yamashita, Luis C. Ho
Abstract
Abstract We present the results of surveying [C i ] 3 P 1 – 3 P 0 , 12 CO J = 4 − 3, and 630 μ m dust continuum emission for 36 nearby ultra/luminous infrared galaxies (U/LIRGs) using the Band 8 receiver mounted on the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array. We describe the survey, observations, data reduction, and results; the main results are as follows. (i) We confirmed that [C i ] 3 P 1 – 3 P 0 has a linear relationship with both the 12 CO J = 4 − 3 and 630 μ m continuum. (ii) In NGC 6052 and NGC 7679, 12 CO J = 4 − 3 was detected but [C i ] 3 P 1 – 3 P 0 was not detected with a [C i ] 3 P 1 – 3 P 0 / 12 CO J = 4 − 3 ratio of ≲0.08. Two possible scenarios of weak [C i ] 3 P 1 – 3 P 0 emission are C 0 -poor/CO-rich environments and an environment with an extremely large [C i ] 3 P 1 – 3 P 0 missing flux. (iii) There is no clear evidence showing that galaxy mergers, AGNs, and dust temperatures control the ratios of [C i ] 3 P 1 – 3 P 0 / 12 CO J = 4 − 3 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mo stretchy="false">[</mml:mo> <mml:mi mathvariant="normal">C</mml:mi> <mml:mspace width="0.25em"/> <mml:mi mathsize="small" mathvariant="normal">I</mml:mi> <mml:mo stretchy="false">]</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo>−</mml:mo> <mml:mn>0</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msubsup> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>630</mml:mn> <mml:mi>μ</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:msub> </mml:math> . (iv) We compare our nearby U/LIRGs with high- z galaxies, such as galaxies on the star formation main sequence (MS) at z ∼ 1 and submillimeter galaxies (SMGs) at z = 2–4. We found that the mean value for the [C i ] 3 P 1 – 3 P 0 / 12 CO J = 4 − 3 ratio of U/LIRGs is similar to that of SMGs but smaller than that of galaxies on the MS.