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Дата индексирования: Sat Sep 11 20:29:26 2010
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Поисковые слова: equinox

Emission-line galaxies

The emission line galaxies observed are listed in Table 3 containing the following information:
column 1: The object's IAU-type name with the prefix HS.
column 2: Right ascension for equinox B1950.
column 3: Declination for equinox B1950. The coordinates were measured on direct plates of the HQS and are accurate to $\sim$ 2$\arcsec$ (Hagen et al. [1995]).
column 4: Heliocentric velocity and its r.m.s. uncertainty in km s^-1.
column 5: Apparent B-magnitude obtained by calibration of the digitized photoplates with photometric standard stars (Engels et al. [1994]), having an r.m.s. accuracy of $\sim$ $0\fm5$ for objects fainter than m$_{\rm B}$ = $16\fm0$ (Popescu et al. [1996]). Since the algorithm to calibrate the objective prism spectra is optimized for point sources the brightnesses of extended galaxies are underestimated. The resulting systematic uncertainties are expected to be as large as 2 mag (Popescu et al. [1996]). For about 1/3 of our objects, B-magnitudes are unavailable at the moment. We present for them blue magnitudes obtained from the APM database. They are marked by a ``plus" before the value in the corresponding column. According to our estimate they are systematically brighter by $0\fm92$ than the B-magnitudes obtained by calibration of the digitized photoplates (r.m.s. $1\fm02$). For all objects marked as from Popescu et al. ([2000]) one may find improved B-magnitudes in Vennik, Hopp & Popescu ([2000]) which we do not list here for the sake of homogeneity.
column 6: Absolute B-magnitude, calculated from the apparent B-magnitude and the heliocentric velocity. No correction for galactic extinction is made as all objects are located at high galactic latitudes and because the corrections are significantly smaller than the uncertainties of the magnitudes.
column 7: Preliminary spectral classification type according to the spectral data presented in this article. BCG means that the galaxy possesses a characteristic H II-region spectrum and that the luminosity is low enough. SBN and DANS are galaxies of lower excitation with a corresponding position in line ratio diagrams, as discussed in Paper I. SBN are the brighter fraction of this type. We here follow the notation of Salzer et al. ([1989]). Seyfert galaxies are separated mainly on diagnostic diagrams as AGN. The criterion of broad lines was also used for the Sy classification. With SA two probable super-association in a spiral and an irregular galaxy are denoted. Two ELGs are difficult to classify. They are coded as NON.
column 8: One or more alternative names, according to the information from NED. References to other sources of spectral information indicating that a galaxy is an ELG are given in bold face.

The spectra of all emission-line galaxies are shown in Appendix A, which is available only in the electronic version of the journal.

The results of line flux measurements are given in Table 4. It contains the following information:
column 1: The object's IAU-type name with the prefix HS. By asterisk we note the objects observed during non-photometric conditions.
column 2: Observed flux (in 10^-16ergs^-1cm^-2) of the H$\beta$ line. For few objects without H$\beta$ emission line the fluxes are given for H$\alpha$ and marked by a ``plus''. For several objects observed during non-photometric conditions this parameter is unreliable and marked by (:).
columns 3,4,5: The observed flux ratios [O II]/H$\beta$, [O III]/H$\beta$ and H$\alpha$/H$\beta$. For few objects without H$\beta$ flux ratios are given for H$\alpha$ and marked by a ``plus''.
columns 6,7: The observed flux ratios [N II]$\lambda$6583 Å/H$\alpha$, and ([S II]$\lambda$6716 Å + $\lambda$6731 Å)/H$\alpha$.
columns 8,9,10: Equivalent widths of the lines [O II]$\lambda$3727 Å, H$\beta$ and [O III]$\lambda$5007 Å. For few objects without detected H$\beta$ emission line the equivalent widths are given for H$\alpha$ and marked by a ``plus''.

Among the 97 ELGs observed as first-priority candidates, 66 are classified as BCGs or probable BCGs. Two very faint objects (HS 1134+3640 and HS 1308+3845) are probably super-associations in the dwarf spiral NGC 3755 and in the Im galaxy UGC 8261. Two ELGs are probable LINERs. One candidate is difficult to classify. The remaining 26 ELGs are objects of lower excitation: either starburst nuclei galaxies (SBN and probable SBN) or their lower mass analogs dwarf amorphous nuclear starburst galaxies (DANS or probable DANS).

Below we give notes on several individual objects:

HS 0847+3639: The HS magnitude for this galaxy seems to be too faint. The KUG magnitude (Takase & Miyauchi-Isobe [1993]) B=154 corresponds to M_B=-196 and an SBN classification as given in Table 3.
HS 0934+3629: The FWHMs, corrected for instrumental resolution, for H$\alpha$ and H$\beta$ are $\approx$1800 km s^-1 and $\approx$1400 km s^-1, respectively.
HS 1047+3714: Very strong N II line $\lambda$6583 Å, H$\beta$ is only seen in absorption.
HS 1116+3951: Uncertain H$\alpha$/H$\beta$ ratio because of a cosmic hit on H$\alpha$.
HS 1134+3639: Probable low-mass companion of the galaxy NGC 3755 (the distance is $\approx$230 or $\sim$25 kpc).
HS 1134+3640: Possible giant H II-region at the very edge of the SAB(rs)c pec galaxy NGC 3755 with V_hel=1570 km s^-1, seen at an inclination angle of $\approx$60$^\circ$. The HI-line width at the level of 0.2 of the peak flux value W_0.2=290 km s^-1 (Huchtmeier & Richter [1989]) corresponds to a maximum V_rot of $\approx$150 km s^-1. In accordance with the difference in radial velocities (-108 km s^-1) of HS 1134+3640 and the dynamical center of NGC 3755, HS 1134+3640 is either an H II-region in NGC 3755, or a companion like HS 1134+3639. The real situation can be checked only if it is determined whether this edge of NGC 3755, corresponds to the receding or approaching spiral arm.
HS 1308+3545: Giant H II-region at the edge of the B=160 Im galaxy UGC 8261 with V_hel=852 km s^-1. Its HI-line width W_0.2=127 km s^-1 corresponds to a maximum V_rot of $\approx$65 km s^-1. This is consistent with the measured difference in the radial velocities of HS 1308+3545 and the dynamical center of the Im galaxy.
HS 1620+4003: The profiles of the O III-lines $\lambda$ 4959,5007 Å have a composite structure with a narrow (FWHM₅₀₀₇ = FWHM$_{H\beta}$) and broad (FWHM = $\approx$1800 km s^-1) component. The broad to narrow component flux ratio is 1.44.