HST photometry: Can UV colors probe the Galaxy ages?
CHIOSI C., VALLENARI A. and BRESSAN A.
Abstract (from CDS):
We present grids of magnitudes and colours for the WFPC2 of the refurbished HST using pass-bands from the far UV to the near infrared, i.e. the filters F170W, F218W, F255W, F300W, F336W, F439W, F450W, F555W, F606W, F702W, F814W, and F850LP. In addition to this, we consider also the filters F150W+F130LP, F175W, F220W and F342W of the old HST in the FOC mode in which a great deal of observations have been taken. The theoretical magnitudes and colours are calculated convolving spectral energy distributions with different metallicity (Z), effective temperature (Teff), and gravity with the pass-band transmission, response of the camera, and telescope assembly. In order to enable an easy usage of the present results we provide tabulations of Bolometric Corrections BC{DELTA}λHST as function of gravity, Teff, and chemical composition for each pass-band under consideration. As already pointed out by Yi et al. (1995PASP..107..273Y), the UV filters suffer from the visible/red-leak problem, which destroys the monotonic relation between colours and Teff and causes serious difficulties to analyze the data. With the aid of the above technique we calculate isochrones in the observational colour-magnitude diagram (CMD) and integrated magnitudes and colours of single stellar populations (SSP). The ages span the range from 18Gyr to 0.01 Gyr. For the sake of brevity, results are described here in some detail limited to the solar chemical composition [Y=0.28 Z=0.020]. In addition to this, we present synthetic CMDs for a composite sample of stars containing both young and old objects as they would appear in various pass-bands. Finally, we address the question whether the variation of the UV colours of elliptical galaxies as a function of the red-shift shows signatures from which one can infer the age and the type of source emitting the UV flux. The goal is achieved looking at the red-shift dependence of colours obtained from the pass-bands F170W, F210W, and F555W at varying the Hubble constant H0 and deceleration parameter q0 defining the model of the Universe. It is found that those colours run differently according to underlying source, i.e either P-AGB or P-AGB plus H-HB and AGB-manque stars (see below for details) and the cosmological parameters. If the UV flux is mainly generated by P-AGB plus H-HB and AGB-manque stars a marked discontinuity in suitable UV colours is expected at the red-shift corresponding to the age of about 5.6Gyr.
(Ref) Object type as listed in the reference "Ref"
(acronym) Object type linked to the acronym according to the original reference
() Anterior to 2007, before we can link the objet type to a reference, or given by the CDS team in some particular cases
Other object types:
G
(2014AJ,LEDA,...),
GiG
(2007ApJ,[CHM2007]),
IR
(IRAS,ISOSS),
AG?
(2020MNRAS),
*
(Gaia)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
Syntax of radial velocity (or/and redshift) is : "value [error] (wavelength) quality bibcode"
value : radial velocity or/and redshift (Heliocentric frame) according to your Output Options
(redshift may be not displayed if the data value is <0 and the database inside value is a radial velocity)
[error] : error of the corresponding value displayed before
(wavelength) : wavelength range of the measurement : Rad, mm, IR, Opt, UV, Xray, Gam or '∼'(unknown)
quality : flag of quality ( A=best quality -> E=worst quality, ∼=unknown quality)
References (1308 between 1850 and 2024) (Total 1308)
Simbad bibliographic survey began in 1850 for stars (at least bright stars) and in 1983 for all other objects (outside the solar system).
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