Merger driven vs. Cold-flow driven Star Formation in Typical High-redshift Galaxies : [CII] Line Observation of Local Analogs of High-redshift Galaxies
One of the biggest challenges in galaxy evolution is to understand how star formation is powered in high-redshift star-forming galaxies. Recent discovery of unusually strong (EW > 500A) Halpha emission in majority of z>4 star-forming galaxies has provided indirect evidence that significant fraction of high-redshift star formation is fueled by mechanisms other than gas-rich merger, suggesting that cold gas accretion is an important source of cold, neutral gas in high-redshift galaxies. FIR cooling lines such as [CII] 158 micron line, produced by the UV stellar radiation like Halpha, afford an efficient probe to study physical properties of the interstellar medium in star-forming galaxies. Therefore, we propose to observe [CII] emission line from local counterparts of high-redshift strong Halpha Emitters to investigate the properties of cold neutral gas in these galaxies and understand how star formation is powered. We request total 11.1 hours of Herschel-PACS observation using Line Spectroscopy AOT for 20 targets, detecting the expected [CII] line with line S-N of >3. Unlike the IR-luminous galaxies or QSOs, HAEs are typical star-forming galaxies at high redshifts thus [CII] observation of local HAEs would provide the first measurement of [CII] and [CII]-FIR ratio of typical high-redshift star-forming galaxies. Thanks to the existing data including spectroscopy, the relationship between the observed [CII] and Halpha, FIR luminosity can be investigated as a function of metallicity, stellar population, extinction, etc. Such relationship would be able to tell whether [CII]-FIR ratio can be used as an indicator that discriminates merger-driven star formation and cold-flow driven star formation. Using the last opportunity of Herschel to access rest-frame FIR cooling lines of local galaxies, this observing program would provide a detailed physical framework for interpretation of future large [CII] surveys in galaxies at hig...her redshifts using existing or planned submm to radio facilities.
Publication
Instrument
PACS_PacsLineSpec_point
Temporal Coverage
2012-09-26T19:26:17Z/2013-03-10T17:03:36Z
Version
SPG v14.2.0
Mission Description
Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
