Title: "Dark'' Gas and "Late-Teen'' Galaxies

Abstract:
I will briefly report on two topics here that will greatly benefit from high sensitivity and high 
resolution millimeter observations, particularly ALMA.
First, the so-called CO-dark molecular gas (DMG). Growing evidence from Planck, Herschel, 
and EGRET have suggested a previous underestimated ISM component, namely DMG, which 
can be as much as 50% to 90% of the total molecular gas in the Milkyway. Better quantification 
and understanding of DMG will significantly impact our understanding for galaxies near and far, 
in terms of fundamental parameters, such the star formation rate (SFR). We have successful 
programs at Arecibo, VLA, and ATCA to explore HI and OH absorption as a sensitive technique 
to measure DMG’s conditions. We have a filler program at ALMA to test CO and HCO+ 
absorption as a way to systematically quantify the DMG throughout the Milkyway.

Second,  WISE selection metal poor Blue Compact Dwarfs (BCD). These  bright mid-IR bright 
BCDs are undergoing a starburst phase in the low metallicity environments, possibly their rst 
major episode of star formation. It is a mystery why the gas in these systems has remained in 
a relatively pristine state with little metal enrichment over the Hubble time and only recently  
exhibiting active star formation. We have detected abundant HI gas with Arecibo in these 
system with Arecibo with gas to stellar mass ratio around 50. We then mapped two of the 
system with GMRT and revealed substantial number of ‘floating’ HI clouds without optical 
or UV counter parts. Our surveys favor the scenario of recent infusing of gas, through such as 
cold flows.