H
                    ii
                    Region Population in a Sample of Nearby Galaxies with Nuclear Activity. I. Data and General Results

AbstractThe Local Group contains a great number of dwarf irregulars and spheroidals, for which the spectroscopy of individual stars can be obtained. Thus, the chemical evolution of these galaxies can be traced, with the only need of finding populations spanning a large age range and such that we can accurately derive the composition. Planetary nebulae (PNe) are old- and intermediate-age star remnants and their chemical abundances can be obtained up to 3-4 Mpc. H ii regions, which are brighter and much easily detected, represent galaxies young content. PNe and H ii regions share similar spectroscopic features and are analysed in the same way. Both are among the best tracers of the chemical evolution allowing to draw the chemical time line of nearby galaxies. The focus in this review are the PN and H ii region populations as constraints to the chemical evolution models and the mass-metallicity relation of the local universe.

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Nuclear Activity in Nearby Galaxies

Annual Review of Astronomy and Astrophysics ◽

10.1146/annurev.astro.45.051806.110546 ◽

2008 ◽

Vol 46 (1) ◽

pp. 475-539 ◽

Cited By ~ 651

Author(s):

Luis C. Ho

Keyword(s):

Nuclear Activity ◽

Nearby Galaxies

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The Population of AGNs in Nearby Galaxies

International Astronomical Union Colloquium ◽

10.1017/s0252921100030414 ◽

2002 ◽

Vol 184 ◽

pp. 13-22

Author(s):

Luis C. Ho

Keyword(s):

Nuclear Activity ◽

Nearby Galaxies ◽

Optical Surveys

AbstractThis contribution reviews the properties of nuclear activity in nearby galaxies, with emphasis on results obtained from current optical surveys and multiwavelength follow-up observations thereof.

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Radio Nuclei in Nearby Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900078189 ◽

1984 ◽

Vol 110 ◽

pp. 251-256

Author(s):

E. Preuss

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Seyfert Galaxies ◽

Instrumental Performance ◽

Nuclear Activity ◽

Normal Galaxies ◽

Nearby Galaxies ◽

The Subject ◽

5 Ghz ◽

Work Done

This review is an attempt to summarize VLBI continuum observations at cm- and dm-wavelengths of active galactic nuclei at distances ≲ 100 Mpc (Ho = 50 km s−1 Mpc−1). ‘Nearby galaxies’, thus defined, are close enough for achieving the highest possible spatial resolution. Galaxies at these distances, however, typically do not show extreme and rare forms of nuclear activity such as powerful radio sources, the cores of which are relatively easy to map with VLBI, and which are therefore the subject of most of the VLBI work done so far (see e.g. Preuss, 1983). Nearby active galaxies show rather more ‘ordinary’ forms of nuclear activity; they include a few of the weaker classical ‘radio galaxies’, but most of them are Seyfert galaxies and mildly active ‘normal galaxies’. Their total radio emission is typically weak (P(5 GHz) ≲ 1031 erg s−1 Hz−1) and so are their compact radio nuclei (if any). The highest available sensitivity is therefore required for their study and the current instrumental performance is just becoming sufficient to tackle the strongest of them in the hope of obtaining maps.

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Nuclear Activity in the Hickson Compact Groups of Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900113324 ◽

1999 ◽

Vol 186 ◽

pp. 418-418

Author(s):

M. Shimada ◽

S. Nishiura ◽

Y. Ohyama ◽

T. Murayama ◽

Y. Taniguchi

Keyword(s):

Emission Line ◽

The Other ◽

Compact Groups ◽

Early Type ◽

Late Type ◽

No Emission ◽

Nuclear Activity ◽

Groups Of Galaxies ◽

Nearby Galaxies ◽

Hickson Compact Groups

In order to study environmental effects on the nuclear activity in galaxies, we have been conducting a spectroscopic study of Hickson Compact Groups of galaxies (HCGs, Hickson 1982) which are the densest agglomeration of galaxies. We obtained nuclear spectra of 62 galaxies in 29 HCGs in the spectral range 6200–7000Å with the 188cm telescope at Okayama Astrophysical Observatory. These spectra were classified into the three types by using the emission line ratio [NII]λ6583/Hα; (1) AGN: [NII]λ6583/Hα >0.6, (2) HII nuclei: [NII]λ6583/Hα <0.6, and (3) Absorption: no emission line. We compared the nuclear activity of galaxies in HCGs with that of nearby galaxies (Ho 1996; Ho, Filippenko & Sargent 1997) which provides a representative sample of field galaxies. In early-type spirals (Sa-Sbc), the fraction of HII nuclei in HCGs is smaller than that in the field galaxies, while the fraction of absorption in HCGs is larger than that in field galaxies. On the other hand, in early-type galaxies (E-S0a) and late-type spirals (Sc-P), we found little difference in the nuclear activity between HCGs and field galaxies.

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