A spatially resolved study of ionized regions in galaxies at different ...

2.3. Results 23
Aperture R eff F(Hα) L(Hα) Q(H 0 ) M ii EW(Hα)
pc 10 −13 erg s −1 cm −2 10 39 erg s −1 10 51 s −1 10 4 M ⊙ Å
NGC5471-1 61.1 6.63 ± 0.31 4.1 4.1 13.0 1187 ± 77
NGC5471-2 60.9 3.07 ± 0.14 1.9 1.9 6.1 993 ± 64
NGC5471-3 47.0 0.93 ± 0.04 0.6 0.6 1.9 354 ± 23
NGC5471-4 51.2 1.59 ± 0.07 1.0 1.0 3.2 1103 ± 71
NGC5471-5 46.0 0.79 ± 0.04 0.5 0.5 1.6 788 ± 51
NGC5471-6 58.9 2.42 ± 0.11 1.5 1.5 4.8 919 ± 59
NGC5471-7 63.1 2.34 ± 0.11 1.5 1.4 4.7 872 ± 57
NGC5471-8 43.5 0.72 ± 0.03 0.5 0.4 1.4 756 ± 49
NGC5471-9 34.0 0.38 ± 0.02 0.2 0.2 0.8 1369 ± 90
NGC5471-10 46.2 1.22 ± 0.06 0.8 0.8 2.4 1282 ± 83
NGC5471-11 53.6 0.31 ± 0.01 0.2 0.2 0.6 585 ± 37
NGC 5471 525 36.5 ± 1.70 23 22 73 783 ± 40
Table 2.4: Integrated Hα flux and derived parameters for the eleven regions of NGC 5471. R eff is
the effective radius of the polygon. The last row belongs to the integrated values of the whole region.
a file with the photometry data and a series of input parameters, such as the model family,
understood as the collection of SED from stellar atmosphere models or synthetic stellar
populations, and the range of the parameters to be used. Then, CHORIZOS reads the model
photometry from the tables calculated previously, interpolates, calculates the likelihood for
each grid point, and write the results for each of the four parameters (mode, mean, standard
deviation, median, . . . ). The program contains a useful module which reads the results and
produces spectra, probability contour plots and additional statistics.
In the case of our study, we have used the STARBURST99 models (Leitherer et al., 1999)
with the implementation by Smith et al. (2002) which includes a grid of blanketed stellar
atmospheres at different metallicities. We fixed two parameters: the known metallicity of
NGC 5471 and the type of dust, leaving unconstrained the amount of extinction and the
age.
Regarding extinction, CHORIZOS works with E(4405 − 5495) and R 5495 , which are the
monochromatic equivalent to E(B − V ) and R V respectively, the values 4405 and 5495
referring to the central wavelength (in Å) of the B and V filters. We used the standard type
of dust characterized by a value R 5495 = 3.1. The metallicity of the region was assumed to
be traced by the oxygen abundance. Recent derivations from detailed spectrophotometric
studies give a mean value of 12+log(O/H) of 8.06 ± 0.03 for components A, C and D;
a slightly lower abundance of 7.94 ± 0.03 is found for component B (Kennicutt et al.,
2003). These values correspond to about 0.25 the solar oxygen abundance, if the value by
Asplund et al. (2005) for the solar oxygen abundance is assumed. Therefore we used the