The 2MASS Red AGN Survey

• R. Cutri, B. Nelson, D. Kirkpatrick (IPAC/Caltech)

• M. Skrutskie (U. Virginia)

• P. Francis (ANU/MSSSO)

• P. Smith. G. Schmidt, D. Hines (U. Arizona)

• J. Huchra, B. Wilkes (Harvard/Smithsonian)

Is There a Population of Obscured AGN?

• Far-IR and Radio surveys suggest 50-80% of AGN in local universe are missed by optical/UV surveys because of dust obscuration

– IRAS QSOs (Low et al. 1997)– Red QSOs from radio surveys (Webster et al. 1995; Francis et al. 1999)– Very red, luminous, high-z FIRST/2MASS AGN (Gregg et al. 2002)– May account for at least part of XRB (e.g. Comastri et al. 1995)

• But UV-excess/optical color-selected surveys appear to be 80-90% complete

–2dF complete spectroscopic survey - 16.5<bj<19.7 (Meyer et al. 2001)

– SDSS QSO survey (Ivezic et al. 2002)

• Conduct a large-scale, uniform IR survey for reddened AGN

Red AGN Search Criteria

• Uniform all-sky photometry of 2MASS provides basis to search for and characterize a population of obscured or intrinsically red AGN

• 95% of known optical/UV/radio-selected QSOs have J-Ks < 2.0

• 2MASS Red AGN candidate selection – 3 band detection, J-Ks > 2

–|b|>30o, exclude SMC/LMC to avoid AGB stars– 20,400 deg2

– 16,997 candidates – Brightest candidates are high-latitude AGB stars– <5% are known AGN

Histograms of J-Ks color (from 2MASS) for (top-to-bottom) PG, northern and southern Hamburg, LBQS and FIRST Bright QSO samples

Preliminary 2MASS Search Results

• Spectroscopic follow-up of 704 (4.1%) candidates

• 69% of observed candidates are Type 1 or Type 2 AGN

– Remainder are starburst or normal galaxies, AGB stars and L-dwarfs – ~5% unclassifiable because of low SNR

• Most of the AGN are Type 1 (e.g. broad-line - QSO/Sy1.x)

– N(type 1)/N(type 2) ~ 4

Number Class Extrap. Surface Density (deg-2)384 Type 1 AGN (Sy1/QSO) 0.45101 Type 2 AGN (Sy2/LINER) 0.1211 Uncertain em-line objects 0.0197 Normal & Starburst Galaxies 0.1167 Stars (AGB and Carbon) 0.084 L-dwarf stars <0.0140 Unidentifiable 0.05

Selection Biases

• Color selection biases search

– Reddest objects missed because flux-limited sample driven by J-band

– Ks<12m missed because resolved

– Dilution by starlight makes blue

• Redshift distribution: 0.03 < z < 2.52

– Most are low z - Median z = 0.22 – k-correction biases to low-z– Peak near J-Ks ~2.2 because H-alpha in Ks

• Extrapolated surface density is

~0.5 red AGN deg-2 @ Ks<14.5

– Incomplete for Ks>13.5

– Corresponds to QSO surface density at bj<18.2 mag (Meyer et al. 2001)

• Detection in other surveys

– 50% detected in FIRST radio survey – 10% detected in Rosat Faint Src. Sur.– 20% detected by IRAS

Properties of the New 2MASS AGN

Cumulative red AGN number counts as a function of Ks magnitude

• LK- Redshift Distribution

– Type 2 AGN lower luminosity

– As expected, IR survey finds highest IR-

luminosity objects– But some optical surveys (e.g. Hamburg/ESO) sample similar Ks-luminosity range

Properties of the New 2MASS AGN

• Ks luminosity function ( 1/Vmax)

– Local space density of 2MASS type 1 AGN comparable to optical/UV selected QSOs at intermediate luminosities

– Drop-off at highest luminosity due to redshift bias (fewer high-z objects in 2MASS sample)

Nature of the 2MASS Red AGN

• Relative near-IR colors of 2MASS red AGN consistent with reddening of optical/UV population

• Optical/near-IR colors are not consistent with simple screen extinction model

• 2MASS Red AGN span very large range of blue-IR color (Bj ~ 15 to >21)

Polarization of 2MASS AGN

Smith, Schmidt, Hines, Cutri, & Nelson

(2002 ApJ, 569, 23)

• 2MASS AGN most strongly polarized sample of radio quiet AGN

– 11/89 2MASS red AGN have optical broadband P>3%, with max P=11% (no PG QSOs have P>3%)– Host galaxy dilutes light in some, so %P lower limit–Intermediate types (1.5-1.9) highest polarized fraction (23%) – Highest degree of polarization seen in reddest objects

• Spectropolarimetry of two 2MASS AGN shows

highly polarized broad lines– Viewing obscured BLR in scattered light

Chandra Observations of 2MASS AGN

Wilkes, Cutri, Hines, Nelson, Schmidt, & Smith (2001 ApJ, 564, L65)

• Subset of Type 1 & 2 AGN with

Ks<13.8 & B-Ks > 4.3– 15/26 with ACIS-I observations– Exposures set to detect 1/800 x prediction based on KX = 2.1

• 2MASS red AGN are absorbed in X-rays

• All are X-ray faint • Hardness ratios - NH ~ 1021-1023

• Even after correction for internal extinction, some are still underluminous in X-rays

Summary

• 2MASS is revealing large numbers of previously unknown, predominantly low redshift, red AGN

– >12,000 expected over the entire sky, ~70% of which will be Sy1/QSO

• Luminosity function implies that space density of intermediate luminosity Type 1 2MASS AGN may be comparable to optical/UV-selected QSOs

– Under-represented in optical/UV searches because too faint in blue/UV (e.g. Francis, Whiting and Webster 2000)

• NIR colors, source counts, polarization properties and X-ray flux and slopes suggest that many 2MASS AGN are red because of obscuration

– But geometry and distribution of dust, origin of continuum at different wavelengths complicates interpretation

• Red AGN may be underluminous in X-rays– Implications for modeling AGN contribution of X-ray background

2MASS Overview

• Highly uniform digital imaging survey of the entire sky in three near IR bands– Identical, dedicated 1.3m telescopes at Mt. Hopkins and CTIO

–Three NICMOS 3 arrays for simultaneous imaging in J(1.25m) H(1.65m) and Ks(2.17m)

• Data Products– Calibrated Image Atlas (~4e6 512x1024 1”/pix FITS images in the 3 survey bands)– Point Source Catalog (astrometry and photometry for ~3.5e8 point sources)

• SNR=10:1 at ~1mJy (J<15.8, H<15.1 Ks<14.3), positional accuracy <0.3" RMS wrt ICRS

– Extended Source Catalog (positions and photometry for ~2e6 resolved sources, mostly galaxies)

• SNR=10:1 at ~4mJy (J<15.0, H<14.6, Ks<13.5)

• Survey Status– 100% of the sky observed (Feb 2001)– Data products covering 48% of the sky now

in public domain – Final data processing of full data set completed

Feb 2002, – Catalog generation and validation in progress– Full-sky data release in Sept 2002

All-sky JHKs composite point source surface density map