J/A+A/519/A40 Spectroscopic study of 65 nearby galaxies (Annibali+, 2010)
Nearby early-type galaxies with ionized gas.
IV. Origin and powering mechanism of the ionized gas.
Annibali F., Bressan A., Rampazzo R., Zeilinger W.W., Vega O., Panuzzo P.
<Astron. Astrophys. 519, A40 (2010)>
=2010A&A...519A..40A 2010A&A...519A..40A
ADC_Keywords: Galaxies, nearby ; Galaxies, optical ; Galaxies, spectra
Keywords: galaxies: elliptical and lenticular, cD - galaxies: ISM -
galaxies: active - galaxies: abundances
Abstract:
With the aim of constraining the source of excitation and the origin
of the ionized gas in early-type galaxies (ETGs), we analyzed
intermediate resolution optical spectra of a sample of 65 ETGs mostly
located in low density environments. Optical emission lines are
detected in 89% of the sample. The incidence and strength of emission
do not correlate either with the E/S0 classification, or with the
fast/slow rotator classification. Comparing the nuclear r<re/16 line
emission with the classical [OIII]/Hb vs [NII]/Ha diagnostic diagram,
the galaxy activity is so classified: 72% of the galaxies with
emission are LINERs, 9% are Seyferts, 12% are Composite/Transition
objects, and 7% are non-classified. Seyferts have young
luminosity-weighted ages (<5Gyr), and appear, on average,
significantly younger than LINERs and Composites. Excluding the
Seyferts from our sample, we find that the spread in the ([OIII], Ha
or [NII]) emission strength increases with the galaxy central velocity
dispersion sigmac. The [NII]/Ha ratio decreases with increasing
galacto-centric distance, indicating either a decrease of the nebular
metallicity, or a progressive "softening" of the ionizing spectrum.
The average oxygen abundance of the ionized gas is slightly less than
solar, and a comparison with the results obtained in Paper III (Cat.
J/A+A/463/455) from Lick indices reveals that it is ∼0.2dex lower than
that of stars. Conclusions: the nuclear emission can be explained with
photoionization by PAGB stars alone only in ∼22% of the
LINERs/Composite sample. On the other hand, we can not exclude an
important role of PAGB star photoionization at larger radii. For the
major fraction of the sample, the nuclear emission is consistent with
excitation from a low-accretion rate AGN, fast shocks (200-500km/s) in
a relatively gas-poor environment (n<100cm-3), or coexistence of the
two. The derived nebular metallicities suggest either an external
origin of the gas, or an overestimate of the oxygen yields by SN
models.
Description:
Fluxes and equivalent widths for the emission lines measured in the
optical spectra of 65 nearby early-type galaxies. The emission lines
are: [OII] λ3727, [NeIII] λ3869, Hβ λ4861,
[OIII] λ4959, [OIII] λ5007, [OI] λ6300, [NII]
λ6548, Hα λ6563, [NII] λ6584, [SII]
λ6717, [SII] λ6731. The emission lines were measured in
4 annuli of increasing galacto-centric distance: r<re/16 (where re is
the effective radius), re/16<r<re/8, re/8<r<re/4, and re/4<r<re/2. The
reddening E(B-V) was derived from the Hβ and Hα emission
lines, assuming flux(Hα)/flux(Hβ)=3.1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 89 65 Sample overview
table2.dat 154 212 Emission line fluxes
table3.dat 141 212 Emission line equivalent widths
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See also:
J/A+A/433/497 : Nearby early-type gal. with ionized gas. I. (Rampazzo+, 2005)
J/A+A/445/79 : Nearby early-type gal. with ionized gas. II. (Annibali+, 2006)
J/A+A/463/455 : Nearby early-type gal. with ionized gas. III. (Annibali+, 2007)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Galaxy Galaxy name
9- 21 A13 --- MType1 RSA (Cat. VII/51) morphological type
23- 35 A13 --- MType2 RC3 (Cat. VII/155) morphological type
38- 40 I3 km/s sigmac ?=- Central velocity dispersion
(from HYPERLEDA, Cat. VII/237)
42- 45 F4.1 arcsec re Effective radius from RC3 (Cat. VII/155)
47- 50 I4 km/s HV Galaxy systemic velocity
52- 55 F4.2 Mpc-3 rho ?=- Richness parameter rhoxyz,
in gal/Mpc3 (1)
57- 60 F4.1 Gyr Age ? Age (from paper II, Cat. J/A+A/445/79)
62- 65 F4.1 Gyr e_Age ? rms uncertainty on Age
67- 71 F5.3 --- Z ? Metallicity (from paper II,
Cat. J/A+A/445/79)
73- 77 F5.3 --- e_Z ? rms uncertainty on Z
79- 82 F4.2 [-] [a/Fe] ? α/Fe abundance ratio (from paper II,
Cat. J/A+A/445/79)
84- 87 F4.2 [-] e_[a/Fe] ? rms uncertainty on [a/Fe]
89 A1 --- Data [*] * when data in tables 2 and 3
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Note (1): It represents the density of galaxies brighter than -16 apparent
B-mag in the vicinity of the entry.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Galaxy Galaxy identifier
9 I1 --- Reg [1/4] Annulus code (G1)
11- 16 F6.2 --- E(B-V) Reddening
18- 22 F5.2 --- e_E(B-V) Error on reddening
24- 29 F6.2 10-19W/m2/arcsec2 FOII ?=99.99 OII 3727 flux (G2)
31- 34 F4.2 10-19W/m2/arcsec2 e_FOII ?=9.99 Error on FOII 3727
36- 41 F6.2 10-19W/m2/arcsec2 FNeIII ?=99.99 NeIII 3869 flux (G2)
43- 46 F4.2 10-19W/m2/arcsec2 e_FNeIII ?=9.99 Error on FNeIII 3869
48- 53 F6.2 10-19W/m2/arcsec2 FHb ?=99.99 Hbeta flux (G2)
55- 58 F4.2 10-19W/m2/arcsec2 e_FHb ?=9.99 Error on FHbeta
60- 65 F6.2 10-19W/m2/arcsec2 FOIII59 ?=99.99 OIII 4959 flux (G2)
67- 70 F4.2 10-19W/m2/arcsec2 e_FOIII59 ?=9.99 Error on FOIII 4959
72- 77 F6.2 10-19W/m2/arcsec2 FOIII07 ?=99.99 OIII 5007 flux (G2)
79- 82 F4.2 10-19W/m2/arcsec2 e_FOIII07 ?=9.99 Error on FOIII 5007
84- 89 F6.2 10-19W/m2/arcsec2 FOI ?=99.99 OI 6300 flux (G2)
91- 94 F4.2 10-19W/m2/arcsec2 e_FOI ?=9.99 Error on FOI 6300
96-101 F6.2 10-19W/m2/arcsec2 FNII48 ?=99.99 NII 6548 flux (G2)
103-106 F4.2 10-19W/m2/arcsec2 e_FNII48 ?=9.99 Error on FNII 6548
108-113 F6.2 10-19W/m2/arcsec2 FHa ?=99.99 Halpha flux (G2)
115-118 F4.2 10-19W/m2/arcsec2 e_FHa ?=9.99 Error on FHalpha
120-125 F6.2 10-19W/m2/arcsec2 FNII84 ?=99.99 NII 6584 flux (G2)
127-130 F4.2 10-19W/m2/arcsec2 e_FNII84 ?=9.99 Error on FNII 6584
132-137 F6.2 10-19W/m2/arcsec2 FSII17 ?=99.99 SII 6717 flux (G2)
139-142 F4.2 10-19W/m2/arcsec2 e_FSII17 ?=9.99 Error on FSII 6717
144-149 F6.2 10-19W/m2/arcsec2 FSII31 ?=99.99 SII 6731 flux (G2)
151-154 F4.2 10-19W/m2/arcsec2 e_FSII31 ?=9.99 Error on FSII 6731
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Galaxy Galaxy identifier
9 I1 --- Reg [1/4] Annulus code (G1)
11- 16 F6.2 0.1nm WOII ?=99.99 OII 3727 equivalent width (G2)
18- 21 F4.2 0.1nm e_WOII ?=9.99 Error on WOII 3727
23- 28 F6.2 0.1nm WNeIII ?=99.99 NeIII 3869 equivalent width (G2)
30- 33 F4.2 0.1nm e_WNeIII ?=9.99 Error on WNeIII 3869
35- 40 F6.2 0.1nm WHb ?=99.99 Hbeta equivalent width (G2)
42- 45 F4.2 0.1nm e_WHb ?=9.99 Error on WHbeta
47- 52 F6.2 0.1nm WOIII59 ?=99.99 OIII 4959 equivalent width (G2)
54- 57 F4.2 0.1nm e_WOIII59 ?=9.99 Error on WOIII 4959
59- 64 F6.2 0.1nm WOIII07 ?=99.99 OIII 5007 equivalent width (G2)
66- 69 F4.2 0.1nm e_WOIII07 ?=9.99 Error on WOIII 5007
71- 76 F6.2 0.1nm WOI ?=99.99 OI 6300 equivalent width (G2)
78- 81 F4.2 0.1nm e_WOI ?=9.99 Error on WOI 6300
83- 88 F6.2 0.1nm WNII48 ?=99.99 NII 6548 equivalent width (G2)
90- 93 F4.2 0.1nm e_WNII48 ?=9.99 Error on WNII 6548
95-100 F6.2 0.1nm WHa ?=99.99 Halpha equivalent width (G2)
102-105 F4.2 0.1nm e_WHa ?=9.99 Error on WHalpha
107-112 F6.2 0.1nm WNII84 ?=99.99 NII 6584 equivalent width (G2)
114-117 F4.2 0.1nm e_WNII84 ?=9.99 Error on WNII 6584
119-124 F6.2 0.1nm WSII17 ?=99.99 SII 6717 equivalent width (G2)
126-129 F4.2 0.1nm e_WSII17 ?=9.99 Error on WSII 6717
131-136 F6.2 0.1nm WSII31 ?=99.99 SII 6731 equivalent width (G2)
138-141 F4.2 0.1nm e_WSII31 ?=9.99 Error on WSII 6731
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Global notes:
Note (G1): Annulus code as follows:
1 = r <re/16
2 = re/16< r <re/8
3 = re/8 < r <re/4
4 = re/4 < r <re/2
Note (G2): Fluxes are expressed in 10-16erg/s/cm2/arcsec2.
A value of 99.99 indicates that the line emission is not provided.
Negative emission values are consistent with no emission.
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Acknowledgements:
Francesca Annibali, francesca.annibali(at)oapd.inaf.it
References:
Rampazzo et al., Paper I 2005A&A...433..497R 2005A&A...433..497R, Cat. J/A+A/433/497
Annibali et al., Paper II 2006A&A...445...79A 2006A&A...445...79A, Cat. J/A+A/445/79
Annibali et al., Paper III 2007A&A...463..455A 2007A&A...463..455A, Cat. J/A+A/463/455
(End) Francesca Annibali [INAF-OAPd], Patricia Vannier [CDS] 01-Jul-2010