References of "Arp, H"
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See detailFurther investigation of the pair of quasars Q0107 - 025 A and B
Surdej, Jean ULg; Arp, H.; Gosset, Eric ULg et al

in Astronomy and Astrophysics (1986), 161

Low and intermediate dispersion spectroscopy of Q0107 - 025 A and B obtained at ESO, AAT, and MMT provide evidence for spectral differences between these two quasars. A redshift difference of 0.004 is ... [more ▼]

Low and intermediate dispersion spectroscopy of Q0107 - 025 A and B obtained at ESO, AAT, and MMT provide evidence for spectral differences between these two quasars. A redshift difference of 0.004 is found between the two objects, and forbidden emission lines due to O II (3727 A), Ne III (1815), and possibly Ne V (3426 A), are seen in the spectrum of Q0107 - 025 A, while only the forbidden Ne III line at 1815 A is possibly detected in the spectdrum of Q0107 - 025 B. No narrow absorption lines could be detected in the 3252 - 5616 A spectral range of the intermediate resolution data of either quasar, and the spectrum of quasar B is found to be steeper in the blue that of the quasar A. The possible presence of a highly redshifted cluster of galaxies in the field of these quasars is suggested by CCD photometry. [less ▲]

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See detailTwo quasars seen near the spiral galaxy NGC 470
Arp, H.; Surdej, Jean ULg; Swings, Jean-Pierre ULg

in Astronomy and Astrophysics (1984), 138

The discovery of two quasars with 16arcsec separation from each other on the sky and within 95arcsec of the nucleus of the spiral galaxy NGC 470 is reported. The quasars were discovered in a search for ... [more ▼]

The discovery of two quasars with 16arcsec separation from each other on the sky and within 95arcsec of the nucleus of the spiral galaxy NGC 470 is reported. The quasars were discovered in a search for ultraviolet-excess objects in four overlapping fields of about 25 square degrees each. Preliminary spectroscopy of the quasars yields z = 1.875 (mv = 19.9 mag) and z = 1.533 (mv = 18.2 mag). [less ▲]

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See detailA new very interesting pair of quasars - Q0107 - 025 A and B
Surdej, Jean ULg; Swings, Jean-Pierre ULg; Henry, A. et al

in 24th Liege International Astrophysical Colloquium: "Quasars and gravitational lenses" (1983)

A search for ultraviolet-excess objects in a field centered around NGC 450 has revealed the presence of two quasar-candidates (18.2 and 17.4 mag) fairly near one another (separation of 77 arcsec ... [more ▼]

A search for ultraviolet-excess objects in a field centered around NGC 450 has revealed the presence of two quasar-candidates (18.2 and 17.4 mag) fairly near one another (separation of 77 arcsec). Preliminary spectroscopy with the Palomar 5 m telescope shows that these objects are indeed two quasars (Q0107 - 025 A and B) having very similar spectra and redshifts (of about 0.96), suggesting a new possible case of twin quasars or of a gravitational lens. Although the analysis (to be published elsewhere) of additional spectroscopic data collected with the ESO 3.6 m telescope rather favors the first interpretation, higher resolution data are still necessary before rejecting definitely the second possibility. Deep multi-color CCD frames obtained with the Danish 1.5 m telescope clearly show that a group (or cluster) of faint galaxies is detected in the vicinity of the two quasars. [less ▲]

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See detailA Survey of Ultraviolet Excess Quasar Candidates in a Large Field around NGC450
Swings, Jean-Pierre ULg; Arp, H.; Surdej, Jean ULg et al

in LIAC Colloq. 24: Quasars and Gravitational Lenses (1983)

Preliminary results of a search for QSO candidates in a 25 square degree field around NGC 450 are presented.

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See detailQuasars in a control field far from bright galaxies
Arp, H.; Surdej, Jean ULg

in Astronomy and Astrophysics (1982), 109

The density of quasars in a control field of the sky selected to be free of bright galaxies is investigated in order to derive a value for the average background density of quasars and to analyze quasar ... [more ▼]

The density of quasars in a control field of the sky selected to be free of bright galaxies is investigated in order to derive a value for the average background density of quasars and to analyze quasar distribution within the field. Schmidt plates were obtained in the ultraviolet and blue for a control field surrounding SAO 45758 at R.A. 15 h 49 min, declination plus 48 deg 38 arcmin. Examination of the spectra of 25 of the 137 objects found to exhibit an ultraviolet excess reveals 12 of them to be quasars, indicating a quasar density of 6.7 plus or minus 0.9/sq deg down to a limiting magnitiude of 20 over the 19 sq deg area of the field. This value is noted to be in agreement with previous values of quasar background density deduced for other regions of the sky. Large fluctuations of quasar density are found, however, within the field which may be correlated with groups of intermediate brightness galaxies. [less ▲]

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