Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theoretical Models for Classical Cepheids: VII. Metallicity effects on
  the Cepheid distance scale   We use theoretical Period-Luminosity and Period-Luminosity-Color relations in
the VI passbands, as based on nonlinear, nonlocal and time-dependent convective
pulsating models, to predict the reddening and true distance modulus of distant
Cepheids observed with the Hubble Space Telescope. By relying on the pulsating
models with metal content Z=0.008, we find that the theoretical predictions
agree to the values obtained by the Extragalactic Distance Scale Key Project on
the basis of empirical Period-Luminosity relations referenced to LMC variables.
In the meantime, from the theoretical relations with Z=0.004 and 0.02 we find
that the predicted E(B-V) and mu_0 decrease as the adopted metal content
increases. This suggests a metallicity correction to LMC-based distances as
given by about -0.27 mag/dex. Such a theoretical correction appears supported
by an existing, although weak, correlation between the Cepheid distance and the
[O/H] metallicity of galaxies within a given group or cluster, as well as by a
similar correlation between the H_0 estimate and the [O/H] metallicity of the
galaxies which calibrate the SNIa luminosity. On the contrary, the metallicity
correction earlier suggested on empirical grounds seem to be excluded.
Eventually we suggest that the average value <H_0> ~ 67 km/s/Mpc provided by
the Key Project team should increase at least up to ~ 69 km/s/Mpc.

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The categories of this paper are: math
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
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The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph