4 research outputs found
Distance to the Active Galaxy NGC 6951 via the Type Ia Supernova 2000E
CCD-photometry and low-resolution spectroscopy of the bright supernova SN
2000E in NGC 6951 are presented. Both the light curve extending up to 150 days
past maximum and the spectra obtained at 1 month past maximum confirm that SN
2000E is of Type Ia. The reddening of SN 2000E is determined as
E(B-V)=0.36+/-0.15, its error is mainly due to uncertainties in the predicted
SN (B-V) colour at late epochs. The V(RI)_C light curves are analyzed with the
Multi-Colour Light Curve Shape (MLCS) method. The shape of the late light curve
suggests that SN 2000E was overluminous by about 0.5 mag at maximum comparing
with a fiducial SN Ia. This results in an updated distance of 33+/-8 Mpc of NGC
6951 (corrected for interstellar absorption). The SN-based distance modulus is
larger by about +0.7 mag than the previous Tully-Fisher estimates. However,
possible systematic errors due to ambiguities in the reddening determination
and estimates of the maximum luminosity of SN 2000E may plague the present
distance measurement.Comment: 9 p., 5 figs, accepted for publication in A&A. A reference correcte
The density of extremely red objects around high-z radio-loud AGN
We present the results of a K-band imaging survey of 40 arcmin^{2} in fields
around 14 radio-loud AGN (6 radio galaxies and 8 quasars) with z>1.5. The
survey, 80% complete to K<19.2 and complemented by R-band imaging, aimed at
investigating whether extremely red objects (EROs) are present in excess around
high-z AGN, and to study the environment of z>1.5 radio galaxies and radio-loud
quasars. At the differential galaxy counts in our fields suggest a
systematic excess over the general field counts. At K<19.2, we find an excess
of galaxies with R-K>6 compared to the general field. Consistently, we also
find that the R-K colour distribution of all the galaxies in the AGN fields are
significantly redder than the colour distribution of the field galaxies. On the
other hand, the distribution of the R-K colours is undistinguishable from that
of galaxies taken from literature fields around radio-loud quasars at 1<z<2. We
discuss the main implications of our findings and we compare the possible
scenarios which could explain our results.Comment: 10 pages, 6 figures, MNRAS, in pres
The Galaxy Population of Cl1601+42 at z=0.54
Photometric redshifts are used to determine the rest frame luminosity
function (LF) of both early-type and late-type galaxies to M_B ~ -17.6 for the
cluster Cl1601+42 at z = 0.54. The total LF shows a steep faint-end slope alpha
\~ -1.4, indicating the existence of a numerous population of dwarf galaxies.
Luminous galaxies, with M_B < -19.5 are mostly red, early-type galaxies, with a
LF best described by a Gaussian. Faint galaxies are predominantly blue,
late-type galaxies, well fitted by a Schechter function with alpha ~ -1.7.
Compared to clusters at lower redshift, the steepening of the faint end starts
at brighter magnitudes for Cl1601+42, which may indicate a brightening of
todays dwarf population relative to the giant population with increasing
redshift. Early-type galaxies are centrally concentrated, and dominate the core
region, implying that the radial gradient of early-type galaxies seen in local
clusters is already established at z ~ 0.5. Bright, late-type galaxies are
rare, consistent with a decrease in star formation in field galaxies as they
are accreted on to the cluster, while faint, blue galaxies are evenly
distributed across the cluster, except for a depletion in the core region. The
blue fraction is f_B ~ 0.15, which is somewhat lower than the Butcher-Oemler
average at z ~ 0.5. The value of f_B is found to increase with limiting
magnitude and with radius from the centre.Comment: 19 pages, 12 figures, accepted by MNRA