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We have used XMM-Newton to observe six Lyman Break Analogs (LBAs): members ofthe rare population of local galaxies that have properties that are verysimilar to distant Lyman Break Galaxies. Our six targets were specificallyselected because they have optical emission-line properties that areintermediate between starbursts and Type 2 (obscured) AGN. Our new X-ray dataprovide an important diagnostic of the presence of an AGN. We find X-rayluminosities of order 10^{42} erg/s and ratios of X-ray to far-IR luminositiesthat are higher than values in pure starburst galaxies by factors ranging from~ 3 to 30. This strongly suggests the presence of an AGN in at least some ofthe galaxies. The ratios of the luminosities of the hard (2-10 keV) X-ray to [OIII]\lambda 5007 emission-line are low by about an order-of-magnitude comparedto Type 1 AGN, but are consistent with the broad range seen in Type 2 AGN.Either the AGN hard X-rays are significantly obscured or the [O III] emissionis dominated by the starburst. We searched for an iron emission line at ~ 6.4keV, which is a key feature of obscured AGN, but only detected emission at the~ 2\sigma level. Finally, we find that the ratios of the mid-infrared (24\mu m)continuum to [O III]\lambda 5007 luminosities in these LBAs are higher than thevalues for Type 2 AGN by an average of 0.8 dex. Combining all these clues, weconclude that an AGN is likely to be present, but that the bolometricluminosity is produced primarily by an intense starburst. If these black holesare radiating at the Eddington limit, their masses would lie in the range of10^5 to 10^6 M_{sun}. These objects may offer ideal local laboratories toinvestigate the processes by which black holes grew in the early universe.

Evidence for Black Hole Growth in Local Analogs to Lyman Break Galaxies