275 research outputs found
Representing colours
How to describe the faded colours in ancient textiles in a way that is understandable to others when no laboratory facilities are available and dye analysis not possible? How do we find names of colours that carry the right connotations to an international readership, and how can we refer to them? The paper discusses challenges posed by these questions and how they have been attempted solved in the Mons Claudianus textile project
The scaling relations of early--type galaxies in clusters I. Surface photometry in seven nearby clusters
This is the first paper of a series investigating the scaling relations of
early-type galaxies in clusters. Here we illustrate the multi-band imagery and
the image reduction and calibration procedures relative to the whole sample of
22 clusters at 0.05 < z < 0.25. We also present the detailed surface photometry
of 312 early-type galaxies in 7 clusters in the first redshift bin,
z~0.025-0.075. We give for each galaxy the complete set of luminosity and
geometrical profiles, and and a number of global, photometric and morphological
parameters. They have been evaluated taking into account the effects of seeing.
Internal consistency checks and comparisons with data in the literature confirm
the quality of our analysis. These data, together with the spectroscopic ones
presented in the second paper of the series, will provide the local calibration
of the scaling relations.Comment: 36 pages, 13 figures, 7 tables, accepted for publication in A&
Spatially resolved spectroscopy of Coma cluster early-type galaxies - II:the minor axis dataset
We present minor axis, off set major axis and one diagonal long slit spectra for 10 E and S0 galaxies of the Coma cluster drawn from a magnitude-limited sample studied before. We derive rotation curves, velocity dispersion profiles and the H-3 and H-4 coefficients of the Hermite decomposition of the line of sight velocity distribution. Moreover, we derive the line index profiles of Mg, Fe and Hbeta line indices and assess their errors. The data will be used to construct dynamical models of the galaxies and study their stellar populations
The Evolution of Cluster Early-Type Galaxies over the Past 8 Gyr
We present the Fundamental Plane (FP) of early-type galaxies in the clusters
of galaxies RXJ1415.1+3612 at z=1.013. This is the first detailed FP
investigation of cluster early-type galaxies at redshift z=1. The distant
cluster galaxies follow a steeper FP relation compared to the local FP. The
change in the slope of the FP can be interpreted as a mass-dependent evolution.
To analyse in more detail the galaxy population in high redshift galaxy
clusters at 0.8<z<1, we combine our sample with a previous detailed
spectroscopic study of 38 early-type galaxies in two distant galaxy clusters,
RXJ0152.7-1357 at z=0.83 and RXJ1226.9+3332 at z=0.89. For all clusters
Gemini/GMOS spectroscopy with high signal-to-noise and intermediate-resolution
has been acquired to measure the internal kinematics and stellar populations of
the galaxies. From HST/ACS imaging, surface brightness profiles, morphologies
and structural parameters were derived for the galaxy sample. The least massive
galaxies (M=2x10^{10}M_{\sun}) in our sample have experienced their most recent
major star formation burst at z_{form}~1.1. For massive galaxies
(M>2x10^{11}M_{\sun}) the bulk of their stellar populations have been formed
earlier z_{form}>~1.6. Our results confirm previous findings by Jorgensen et
al. This suggests that the less massive galaxies in the distant clusters have
much younger stellar populations than their more massive counterparts. One
explanation is that low-mass cluster galaxies have experienced more extended
star formation histories with more frequent bursts of star formation with
shorter duration compared to the formation history of high-mass cluster
galaxies.Comment: 6 pages, 2 figures, Talk for "Matter Cycles of Galaxies in Clusters",
presented at JENAM 2008, Vienna, to be published in Astronomische Nachrichten
in Nov 2009 (proceedings of Symposium 6 of the JENAM 2008, Vienna
The Faber-Jackson relation for early-type galaxies: Dependence on the magnitude range
We take a sample of early-type galaxies from the Sloan Digital Sky Survey
(SDSS-DR7, 90 000 galaxies) spanning a range of approximately 7 in
both and filters and analyse the behaviour of the Faber-Jackson
relation parameters as functions of the magnitude range. We calculate the
parameters in two ways: i) We consider the faintest (brightest) galaxies in
each sample and we progressively increase the width of the magnitude interval
by inclusion of the brighter (fainter) galaxies
(increasing-magnitude-intervals), and ii) we consider narrow-magnitude
intervals of the same width ( ) over the whole magnitude
range available (narrow-magnitude-intervals). Our main results are that: i) in
both increasing and narrow-magnitude-intervals the Faber-Jackson relation
parameters change systematically, ii) non-parametric tests show that the
fluctuations in the values of the slope of the Faber-Jackson relation are not
products of chance variations. We conclude that the values of the Faber-Jackson
relation parameters depend on the width of the magnitude range and the
luminosity of galaxies within the magnitude range. This dependence is caused,
to a great extent by the selection effects and because the geometrical shape of
the distribution of galaxies on the plane depends on
luminosity. We therefore emphasize that if the luminosity of galaxies or the
width of the magnitude range or both are not taken into consideration when
comparing the structural relations of galaxy samples for different wavelengths,
environments, redshifts and luminosities, any differences found may be
misinterpreted.Comment: 15 pages, 5 figures. A&A. Accepte
The Archaeology of Textiles – Recent advances and new methods
Arheologija tekstila doživljava nagli razvoj posljednjih godina. U članku se predstavlja pregled dosadašnjih saznanja o prapovijesnom europskom tekstilu, prikazuju se recentna dostignuća u metodama analize, kao što su analiza vlakana i boja, datiranje radioaktivnim ugljikom te analiza izotopa stroncija koja bi mogla pridonijeti određivanju podrijetla tekstilnih vlakana kao što su vuna, lan ili kopriva. Raspravlja se i o eksperimentalnoj arheologiji kao metodi proučavanja tekstila.Archaeology of textiles has seen rapid development in recent years. The paper presents an overview of current knowledge on prehistoric textiles from Europe, surveying recent advances in methods of analysis such as fibre and dyes analysis, radiocarbon dating, and strontium isotope analysis that is promising to allow provenancing of textile fibres such as wool, fax or nettle. Experimental archaeology as a tool in textile studies will also be discussed
En glemt skat: Miranda Bødtkers tegninger af arkæologiske tekstiler
Over many years, illustrator Miranda Bødtker (1896–1996) carried out drawings for botanists, zoologists and archaeologists at Bergen Museum, the University of Bergen. After her death, thousands of drawings were discovered in her estate. Among them were numerous unpublished drawings of archaeological textiles from five sites. Bødtker’s illustrations show that although several scholars have studied the textiles, none had seen them all. This applies in particular to textiles from two Viking Age burials, Grønhaug and Dale, both of which comprise remains of figured tapestries that are hardly mentioned in archaeological literature. Grønhaug, and a boat from Halsnøy also offer several types of textiles related to the maritime world. The paper presents Bødtker’s drawings and discusses how they compare with published descriptions of those textiles, with drawings of textiles from the Oseberg burial, and to what degree this form of documentation meets current scientific demands.publishedVersio
Spatially resolved spectroscopy of Coma cluster early -- type galaxies: III. The stellar population gradients
We derive central values and logarithmic gradients for the Hbeta, Mg and Fe
indices of 35 early-type galaxies in the Coma cluster. We find that pure
elliptical galaxies have on average slightly higher velocity dispersions, lower
Hbeta, and higher metallic line-strengths than galaxies with disks (S0). The
gradients strongly correlate with the gradients of sigma, but only weakly with
the central index values and galaxy velocity dispersion. Using stellar
population models with variable element abundance ratios from Thomas, Maraston
& Bender (2003a) we derive average ages, metallicities and [alpha/Fe] ratios in
the center and at the effective radius. We find that the [alpha/Fe] ratio
correlates with velocity dispersion and drives 30% of the Mg-sigma relation,
the remaining 70% being caused by metallicity variations. We derive negative
metallicity gradients (-0.16 dex per decade) that are significantly flatter
than what is expected from gaseous monolithic collapse models, pointing to the
importance of mergers in the galaxy formation history. The gradients in age are
negligible, implying that no significant residual star formation has occurred
either in the center or in the outer parts of the galaxies, and that the
stellar populations at different radii must have formed at a common epoch. For
the first time we derive the gradients of the [alpha/Fe] ratio and find them
very small on the mean. Hence, [alpha/Fe] enhancement is not restricted to
galaxy centers but it is a global phenomenon. Our results imply that the
Mg-sigma local relation inside a galaxy, unlike the global Mg-sigma relation,
must be primarily driven by metallicity variations alone.Comment: 19 pages, 8 figures, Accepted for publication in A&
Abundance ratios in hierarchical galaxy formation
The chemical enrichment and stellar abundance ratios of galaxies which form
in a hierarchical clustering scheme are calculated. For this purpose I adopt
the star formation histories (SFH) as they are delivered by semi-analytic
models in Kauffmann (1996}. It turns out that the average SFH of cluster
ellipticals does not yield globally alpha-enhanced stellar populations. The
star burst that occurs when the elliptical forms in the major merger plays
therefore a crucial role in producing alpha-enhancement. Only under the
assumption that the IMF is significantly flattened with respect to the Salpeter
value during the burst, a Mg/Fe overabundant population can be obtained. In
particular for the interpretation of radial gradients in metallicity and
alpha-enhancement, the mixing of global and burst populations are of great
importance. The model predicts bright field galaxies to be less alpha-enhanced
than their counterparts in clusters.Comment: 7 pages, 3 figures, accepted by MNRA
Line-of-sight velocity distribution corrections for Lick/IDS indices of early-type galaxies
We investigate line-of-sight velocity distribution (LOSVD) corrections for
absorption line-strength indices of early-type galaxies in the Lick/IDS system.
This system is often used to estimate basic stellar population parameters such
as luminosity weighted ages and metallicities. Using single stellar population
model spectral energy distributions by Vazdekis (1999) we find that the LOSVD
corrections are largely insensitive to changes in the stellar populations for
old galaxies (age >3 Gyr). Only the Lick/IDS Balmer series indices show an
appreciable effect, which is on the order of the correction itself.
Furthermore, we investigate the sensitivity of the LOSVD corrections to
non-Gaussian LOSVDs. In this case the LOSVD can be described by a Gauss-Hermite
series and it is shown that typical values of h_3 and h_4 observed in
early-type galaxies can lead to significant modifications of the LOSVD
corrections and thus to changes in the derived luminosity weighted ages and
metallicities. A new, simple parameterisation for the LOSVD corrections, taking
into account the h_3 and h_4 terms, is proposed and calibrations given for a
subset of the Lick/IDS indices and two additional indices applicable to old (>3
Gyr) stellar populations.Comment: 10 pages, 8 figures, accepted by A&
- …