Nature 314, 240 - 242 (21 March 1985); doi:10.1038/314240a0

Infrared Seyferts: a new population of active galaxies?

M. H. K. de Grijp^*†, G. K. Miley^†‡, J. Lub^† & T. de Jong^§

^*ESTEC-SA, Postbus 299, 2200 AG Noordwijk, The Netherlands
^†Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, The Netherlands
^‡Space Telescope Science Institute, Homewood Campus, The Johns Hopkins University, Baltimore, Maryland 21218, USA
^§Sterrenkundig Instituut, Universiteit van Amsterdam, Roetersstraat 15, 1018 WB Amsterdam, The Netherlands

A Seyfert spectrum is one of the most important indicators of nuclear activity in galaxies. It is characterized by broad emission lines with high ionization. Most known Seyferts have been found indirectly, for example, by the presence of a strong ultraviolet continuum (Markarian galaxies) or of intense radio emission (broad/narrow-line radio galaxies). Here, we present a new method for finding hitherto unknown Seyferts based on their mid-infrared spectra and we show using data from the Infrared Astronomical Satellite (IRAS) that this method has a success rate of 70%. One Seyfert, so discovered, contains the most luminous infrared nucleus known so far. X-ray surveys are also an efficient means of finding new Seyferts and QSOs (quasistellar objects)^1,2, but tend to reveal samples at considerably higher redshifts and lower space density. We believe that 'infrared' Seyferts may soon out-number those detected by other methods.

References

1.	Stocke, J. T. et al. Astrophys. J. 273, 458−477 (1983). | Article | ISI | ChemPort |
2.	Gioia, I. M. et al. Astrophys. J. 283, 495−511 (1984). | Article | ISI | ChemPort |
3.	Neugebauer, G. et al. Astrophys. J. Lett. 278, L1−L6 (1984). | Article |
4.	Soifer, B. T. et al. Astrophys. J. Lett. 278, L71−L74 (1984). | Article |
5.	Young, E. et al. Astropys. J. Lett. 278, L75−L78 (1984). | Article |
6.	Habing, H. J. et al. Astrophys. J. Lett. 278, L59−L62 (1984). | Article | ChemPort |
7.	De Jong, T. et al. Astrophys. J. Lett. 278, L67−L70 (1984). | Article |
8.	Rieke, G. H. & Low, F. J. Astrophys. J. Lett. 199, L13−L17 (1975). | Article |
9.	Simon, T. & Dyck, H. M. Mon. Not. R. astr. Soc. 172, 19P−21P (1975).
10.	Jameson, R. F., Longmore, A. J., McLinn, J. A. & Woolf, N. J. Astrophys. J. Lett. 187, L109 (1974). | Article |
11.	Jones, T. W., Leung, C. M., Gould, R. J. & Stein, W. A. Astrophys. J. 212, 51−59 (1977). | Article |
12.	Miley, G. K. et al. Astrophys. J. Lett. 278, L79−L81 (1984). | Article |
13.	Neugebauer, G. et al. Astrophys. J. Lett. 278, L83−L85 (1984). | Article |
14.	IRAS Circ. 11 Astr. Astrophys. 134, C5 (1984).
15.	Baldwin, J. A., Phillips, M. M. & Terlevich, R. Publs astr. Soc. Pacif. 93, 5−19 (1981). | Article | ChemPort |
16.	Feldmann, F. R., Weedman, D. W., Balzano, V. A. & Ramsey, L. W. Astrophys. J. 256, 427−434 (1982). | Article |
17.	Véron, M. P. Astr. Astrophys. 100, 12−19 (1981). | ISI |
18.	Shuder, J. M. & Osterbrock, D. E. Astrophys. J. 250, 55−65 (1981). | Article | ISI | ChemPort |
19.	Heckman, T. M., Miley, G. K. & Green, R. F. Astrophys. J. 281, 525−534 (1984). | Article | ISI | ChemPort |
20.	IRAS Circ. 16 Astr. Astrophys. (in the press).
21.	IRAS Circ. 6 Astr. Astrophys. 131, C1 (1984).
22.	Beichman, C. et al. Astrophys. J. Lett. (in the press).
23.	Véron-Cetty, M. P. & Véron, P. European Southern Observatory Sci. Rep. 1, (1984).
24.	Meurs, E. J. A. & Wilson, A. S. Astr. Astrophys. (in the press).