For refcode 2006A&A...452..423P: Retrieve 26 NED objects in this reference. Please click here for ADS abstract
NED Abstract
Copyright by European Southern Observatory (ESO).
Reproduced by permission
2006A&A...452..423P
The extragalactic Cepheid bias: a new test using the
periodluminositycolor relation
G. Paturel and P. Teerikorpi
Received 16 November 2005 / Accepted 9 February 2006
We use the PeriodLuminosityColor relation (PLC) for Cepheids to test
for the existence of a bias in extragalactic distances derived from the
classical PeriodLuminosity (PL) relation.
We calculate the parameters of the PLC using several galaxies observed
with the Hubble Space Telescope and show that this calculation must be
conducted with a PLC written in a form where the parameters are
independent. The coefficients thus obtained are similar to those derived
from theoretical models.
Calibrating with a few unbiased galaxies, we apply this PLC to all
galaxies of the Hubble Space Telescope Key Program (HSTKP) and compare
the distance moduli with those published by the HSTKP team. The new
distance moduli are larger (more exactly, the larger the distance the
larger the difference), consistent with a bias.
Further, the bias trend that is observed is the same previously obtained
from two independent methods based either on the local Hubble law or on
a theoretical model of the bias.
The results are quite stable but when we force the PLC relation closer
to the classical PL relation by using unrealistic parameters, the
agreement with HSTKP distance moduli is retrieved. This also suggests
that the PL relation leads to biased distance moduli.
The new distance moduli reduce the scatter in the calibration of the
absolute magnitude of supernovae SNIa at their maximum. This may also
suggest that the relation between the amplitude at maximum and the decay
of the light curve {DELTA} m_15_ may not be as strong as believed.
Key words: Cepheids, distance scale, methods: statistical
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