A QSO survey via optical variability and zero proper motion in the M 92 field
III. Narrow emission line galaxies
Thüringer Landessternwarte Tautenburg, 07778 Tautenburg, Germany e-mail: meus@tls-tautenburg.de, brunz@tls-tautenburg.de
Corresponding author: H. Meusinger, meus@tls-tautenburg.de
Received:
26
November
2001
Accepted:
13
May
2002
We study a sample of 23 narrow-emission line galaxies (NELGs)
which were selected by their strong variability
as QSO candidates in the framework of a
variability-and-proper motion QSO survey on digitised Schmidt plates.
In previous work, we have shown that variability is an
efficient method to find AGNs. The variability properties of
the NELGs are however significantly different from those
of the QSOs. The main aim of this paper is to clarify
the nature of this variability and to estimate the fraction of
AGN-dominated NELGs in this sample.
New photometric and spectroscopic observations
are presented, along with revised data from the
photographic photometry. The originally measured high variability
indices could not be confirmed. The diagnostic line-ratios of
the NELG spectra are consistent with 
region-like spectra.
No AGN could be proved, yet we cannot rule out the existence of
faint low-luminosity AGNs masked by regions from
intense star formation.
Key words: galaxies: active / galaxies: starburst / quasars: emission lines
© ESO, 2002