New results from a near-infrared search for hidden broad-line regions in ultraluminous infrared galaxies

被引:168
作者
Veilleux, S [1 ]
Sanders, DB
Kim, DC
机构
[1] Univ Maryland, Dept Astron, College Pk, MD 20742 USA
[2] Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA
[3] CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA
关键词
galaxies : active; galaxies : Seyfert; galaxies : starburst; infrared : galaxies;
D O I
10.1086/307635
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
This paper reports the latest results from a near-infrared search for hidden broad-line regions (BLRs: Delta V-FWHM greater than or similar to 2000 km s(-1)) in ultraluminous infrared galaxies (ULIGs). The new sample contains 39 ULIGs from the 1 Jy sample selected for their lack of BLRs at optical wavelengths. Broad Paa emission is detected for the first time in two sources-F05189-2524 and F13305-1739. Broad Pact emission may also be present in three other sources-F13443 + 0802SW, F14394 + 5332, and F16156 + 0146-but new data are needed to make sure that H-2 1.8665, 1.8721 mu m are not contributing to this excess emission. The [Si VI] feature, a strong indicator of AGN activity, appears to be present in one object-F13305 - 1739-and perhaps also in Mrk 273 and F13454-2956. In addition, the presence of a hidden BLR is confirmed in the lower luminosity source F11058-1131. The results from this new study are combined with those from our previously published survey to produce a large database on 64 (non-Seyfert 1) ULIGs from the 1 Jy sample. All of the galaxies with strong evidence for a hidden BLR at near-infrared wavelengths present an optical Seyfert 2 spectrum. Overall, at least 50% (and perhaps up to 70%) of the optical Seyfert 2 galaxies in the combined sample present either a BLR or strong [Si VI] emission. In contrast, none of the 41 optically classified LINERs and H II galaxies in the sample shows any obvious signs of an energetically important AGN. Galaxies with "warm" IRAS colors (f(25)/f(60) greater than or similar to 0.2) show a tendency to harbor obscured BLRs in the near-infrared and to have large Pa alpha-to-infrared luminosity ratios. These results support those of our earlier survey and suggest that the screen of dust in most warm Seyfert 2 galaxies is optically thin at 2 mu m. When the results from this near-infrared survey are combined with those from a recent optical spectroscopic study of the entire 1 Jy sample of 118 ULIGs, we find that the fraction of all ULIGs with optical or near-infrared signs of genuine AGN activity (either a BLR or [Si VI] emission) is at least 20%-25% but reaches 35%-50% for objects with L-IR > 10(12.3) L.. Comparisons of the dereddened emission-line luminosities of the optical or obscured BLRs detected in the ULIGs of the 1 Jy sample with those of optical quasars indicate that the obscured AGNs/quasars in ULIGs is the main source of energy in at least 15%-25% of all ULIGs in the 1 Jy sample. This fraction is closer to 30%-50% among ULIGs with L-IR > 10(12.3) L.. These results are compatible with those from recent mid-infrared spectroscopic surveys carried out with ISO.
引用
收藏
页码:139 / 156
页数:18
相关论文
共 33 条
[1]   UNIFIED MODELS FOR ACTIVE GALACTIC NUCLEI AND QUASARS [J].
ANTONUCCI, R .
ANNUAL REVIEW OF ASTRONOMY AND ASTROPHYSICS, 1993, 31 :473-521
[2]   THE DETECTION OF WOLF-RAYET STARS IN A VERY POWERFUL FAR-INFRARED GALAXY - DIRECT EVIDENCE FOR A STARBURST [J].
ARMUS, L ;
HECKMAN, TM ;
MILEY, GK .
ASTROPHYSICAL JOURNAL, 1988, 326 (02) :L45-L49
[3]   FLUORESCENT EXCITATION OF INTERSTELLAR H2 [J].
BLACK, JH ;
VANDISHOECK, EF .
ASTROPHYSICAL JOURNAL, 1987, 322 (01) :412-449
[4]   ATLAS OF QUASAR ENERGY-DISTRIBUTIONS [J].
ELVIS, M ;
WILKES, BJ ;
MCDOWELL, JC ;
GREEN, RF ;
BECHTOLD, J ;
WILLNER, SP ;
OEY, MS ;
POLOMSKI, E ;
CUTRI, R .
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 1994, 95 (01) :1-68
[5]   What powers ultraluminous IRAS galaxies? [J].
Genzel, R ;
Lutz, D ;
Sturm, E ;
Egami, E ;
Kunze, D ;
Moorwood, AFM ;
Rigopoulou, D ;
Spoon, HWW ;
Sternberg, A ;
Tacconi-Garman, LE ;
Tacconi, L ;
Thatte, N .
ASTROPHYSICAL JOURNAL, 1998, 498 (02) :579-605
[6]   SPECTROSCOPY OF LUMINOUS INFRARED GALAXIES AT 2 MICRONS .1. THE ULTRALUMINOUS GALAXIES (L(IR)-GREATER-THAN-OR-SIMILAR-TO-10(12)L(CIRCLE-DOT)) [J].
GOLDADER, JD ;
JOSEPH, RD ;
DOYON, R ;
SANDERS, DB .
ASTROPHYSICAL JOURNAL, 1995, 444 (01) :97-112
[7]   Spectroscopy of luminous infrared galaxies at 2 microns .3. Analysis for galaxies with log (L(IR)/L(circle dot)) greater than or similar to 11.2 [J].
Goldader, JD ;
Joseph, RD ;
Doyon, R ;
Sanders, DB .
ASTROPHYSICAL JOURNAL, 1997, 474 (01) :104-120
[8]   Spectroscopy of luminous infrared galaxies at 2 microns .2. Data for galaxies with 11.2 less than or similar to log (L(IR)/L(circle dot)less than or similar to 11.9 [J].
Goldader, JD ;
Joseph, RD ;
Doyon, R ;
Sanders, DB .
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 1997, 108 (02) :449-470
[9]   INFRARED-SPECTROSCOPY OF SEYFERT-2 GALAXIES - A LOOK THROUGH THE OBSCURING TORUS [J].
GOODRICH, RW ;
VEILLEUX, S ;
HILL, GJ .
ASTROPHYSICAL JOURNAL, 1994, 422 (02) :521-536
[10]   IRAS OBSERVATIONS OF GALAXIES IN THE VIRGO CLUSTER AREA [J].
HELOU, G ;
KHAN, IR ;
MALEK, L ;
BOEHMER, L .
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 1988, 68 (02) :151-172