Compact Composite AGN-Starbursts: hidden AGN or slow starburst-driven shocksquestionMark

We propose observations of a sample of IRselected galaxies dominated by apowerful starburst but where a hidden AGN may enhance the optical emission lineratios. Recent models, however, have shown that objects of composite type couldbe falsely flagged as hosting an AGN in the presence of shocks associated withstarburst superwinds. Radio VLBI observations on the IRselected sources pointto a lack of AGN, and thus favoring the shockinterpretation for these sources.These observations will increase the current sample with good XMM data and willdetermine whether black holes are accreting and dominating the Xray emission inthese starbursts. This would aid in determining at what level AGN are present inobjects of compositetype spectra at low redshift. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]