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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
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:
FileName Lrecl Records Explanations
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
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
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 rho_xyz_, 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
Note (1): It represents the density of galaxies brighter than -16 apparent B-mag in the vicinity of the entry.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
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
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.
Acknowledgements: Francesca Annibali, francesca.annibali(at)oapd.inaf.it References: Rampazzo et al., Paper I 2005A&A...433..497R, Cat. J/A+A/433/497 Annibali et al., Paper II 2006A&A...445...79A, Cat. J/A+A/445/79 Annibali et al., Paper III 2007A&A...463..455A, Cat. J/A+A/463/455
(End) Francesca Annibali [INAF-OAPd], Patricia Vannier [CDS] 01-Jul-2010
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