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Дата изменения: Wed Apr 14 14:21:18 1999
Дата индексирования: Sat Sep 11 20:32:02 2010
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Поисковые слова: carl sagan

Discussion

Altogether we have observed 209 objects preselected as ELG candidates on HQS objective prism plates, of which 196 had no previous spectroscopic information. 134 (64 %) are found to be either ELGs, or quasars. Of 128 detected ELGs 108 were classified on the character of their spectra and their absolute magnitudes as BCGs or probable BCGs. One galaxy showing broad H$\alpha$ (FWHM = 1800 kms^-1) and H$\beta$(FWHM = 1400 kms^-1) and wide and strong He II$\lambda$4686 (I(He II)/I(H$\beta$) $\sim$ 0.7) is a Seyfert galaxy (HS 1057+4632). One very faint object (HS 0811+4913) of absolute magnitude M _B= -11.4 is probably a super-association in the dwarf spiral NGC 2541. Two galaxies show emission line ratios characteristic for LINERs. Two are difficult to classify. The remaining 14 ELGs are objects of lower excitation: either Starburst Nuclei galaxies (SBN) or their lower mass analogs Dwarf Amorphous Nuclear Starburst galaxies (DANS) (Salzer et al. [1989]). Since the main goal of the HSS is an efficient search for new BCGs, the fraction of this type among all new detected ELGs - 84 %, or 80 % among all emission-line objects, is very encouraging.

It is worth to note that after the analysis of the results of pilot part of the HSS (see Paper I), the selection algorithm was improved in order to clean the candidate lists for follow-up spectroscopy from the majority of stellar-like and second priority objects. The majority of the former have been found as blue stars, and the latter are either low excitation ELG or galaxies without emission lines. The overall detection efficiency of emission-line objects has grown significantly, up to 64 % for this second part of the HSS.

The distributions of the new HSS ELGs in the line-ratio diagrams [O III]$\lambda$5007/H$\beta$ versus [N II]$\lambda$6583/H$\alpha$ and [O III]$\lambda$5007/H$\beta$ versus [O II]$\lambda$3727/[O III]$\lambda$5007 (see Baldwin et al. ([1981]), Veilleux & Osterbrock ([1987]) for details) in general are similar to those shown in Paper I. Several new high excitation BCGs are discovered or rediscovered. Follow-up spectroscopy with high signal-to-noise of these prominent galaxies resulted in the discovery of new very metal-poor galaxies. This data will appear in separate papers currently in preparation.

One more immediate conclusion comes from the absolute magnitudes of new the ELGs in Table 2. Even with some reservations concerning the accuracy of the apparent magnitudes, the Hamburg/SAO Survey picks up well objects with M $_{B} \geq -15$. Thus, with additional photometry to improve the accuracy of B-magnitudes, this sample will serve as an important instrument to study the still poorly known faint end of the ELG luminosity function.

Altogether in Paper I and in the present paper we discovered 176 new emission-line objects (10 of them QSOs), and for 32 more galaxies we got quantitative data for their emission lines. Preliminary classification of the 198 ELGs yields 155 confident or probable blue compact/low-mass H II-galaxies. Thus a large fraction of BCGs relative to all ELGs is found ($\sim$ 78 %) demonstrating the high efficiency of this survey to find on the Hamburg Quasar Survey photoplates namely galaxies with H II-type spectra. A statistical analysis of this BCG sample, supplemented with galaxies from the next parts of the survey is underway.