QSOs in the 2 Micron All-Sky Survey
The Two Micron All-Sky Survey (2MASS) will detect QSOs. For example, all of the PG QSOs will be detected by 2MASS in J, H and K s at a SNR> 10. During prototyping observations for 2MASS, 40 QSOs with redshifts in the range 0.1 < z < 3.1 were serendipitously detected in at least one of the survey bands. Thus, 2MASS will produce a highly uniform set of near infrared photometry for a wide variety radio, optical, ultraviolet and X—ray detected QSOs. 2MASS also has the potential to reveal large numbers of previously unknown AGN. Because QSOs occupy distinct regions of near infrared and infrared-optical color space, it will be possible to carry out highly efficient automated searches of the 2MASS databases in combination with newly available digitized optical sky survey databases for candidates. We review the near IR and optical/IR properties of “conventional” QSOs from UV and optical samples, and estimate the number that will be detected by 2MASS. At minimum, it should be possible to find the southern hemisphere equivalents of the UV-excess PG QSOs (≈100 new QSOs in the area b < 30 deg. There is growing evidence for the existence of a significant population of highly reddened QSOs from IRAS and radio—based surveys (e.g. Low et al. 1988, ApJ, 327, L41; Webster et al. 1995, Nature, 375, 469; Gregg et al. 1996, AJ, 112, 407). The infrared and radio surveys suggest that UV—selected searches for QSOs, such as the PG-survey, underestimate by factors of 2–5 the space density of even nearby QSOs. Thus, 2MASS may reveal between several hundred and several thousand new, red QSOs. We discuss 2MASS’s ability to test for such new populations of QSOs based on a variety of models of their space density and luminosity function. Finally, we discuss preliminary infrared/infraredoptical color searches and spectroscopic follow-up of new QSO candidates drawn from the 2MASS Prototype Camera database.