Bodo Ziegler | University of Vienna (original) (raw)
Papers by Bodo Ziegler
Astronomy & Astrophysics, 2014
We describe and discuss the selection procedure and statistical properties of the galaxy sample u... more We describe and discuss the selection procedure and statistical properties of the galaxy sample used by the Calar Alto Legacy Integral Field Area Survey (CALIFA), a public legacy survey of 600 galaxies using integral field spectroscopy. The CALIFA 'mother sample' was selected from the Sloan Digital Sky Survey (SDSS) DR7 photometric catalogue to include all galaxies with an r-band isophotal major axis between 45 and 79.2 and with a redshift 0.005 < z < 0.03. The mother sample contains 939 objects, 600 of which will be observed in the course of the CALIFA survey. The selection of targets for observations is based solely on visibility and thus keeps the statistical properties of the mother sample. By comparison with a large set of SDSS galaxies, we find that the CALIFA sample is representative of galaxies over a luminosity range of −19 > Mr > −23.1 and over a stellar mass range between 10 9.7 and 10 11.4 M . In particular, within these ranges, the diameter selection does not lead to any significant bias against -or in favour of -intrinsically large or small galaxies. Only below luminosities of Mr = −19 (or stellar masses < 10 9.7 M ) is there a prevalence of galaxies with larger isophotal sizes, especially of nearly edge-on late-type galaxies, but such galaxies form < 10% of the full sample. We estimate volume-corrected distribution functions in luminosities and sizes and show that these are statistically fully compatible with estimates from the full SDSS when accounting for large-scale structure. For full characterization of the sample, we also present a number of value-added quantities determined for the galaxies in the CALIFA sample. These include consistent multi-band photometry based on growth curve analyses; stellar masses; distances and quantities derived from these; morphological classifications; and an overview of available multi-wavelength photometric measurements. We also explore different ways of characterizing the environments of CALIFA galaxies, finding that the sample covers environmental conditions from the field to genuine clusters. We finally consider the expected incidence of active galactic nuclei among CALIFA galaxies given the existing pre-CALIFA data, finding that the final observed CALIFA sample will contain approximately 30 Sey2 galaxies.
Our spectroscopic observations were spread across 5 nights in October and November 2004 for Cl 04... more Our spectroscopic observations were spread across 5 nights in October and November 2004 for Cl 0412, 7 nights in December 2005 and February 2005 for MS 1008, 5 nights between May and July 2005 for MS 2137. For photometric data, we use both VLT/FORS2 and HST/ACS images. We obtained imaging of the MS 1008, MS 2137 and Cl 0412 samples in the ACS/F606W filter while we exploited existing imaging of MS 0451 in the ACS/F814W filter from the ST-ECF HST archive. Ground based images were taken in the B, V, R and I filters for the whole sample. The FORS2 filters B, V and I are close approximations to the Johnson-Cousins photometric system while the R filter is a special filter for FORS2 that is similar to the Cousins R . (5 data files).
Proceedings of the International Astronomical Union, 2006
Most of the galaxies in the local universe are located in groups, in particular in small groups, ... more Most of the galaxies in the local universe are located in groups, in particular in small groups, and most of the transformations suffered by galaxies located in today's clusters are likely to have occurred in groups at higher redshifts. Understanding the formation and evolution of groups is essential to understand the whole picture of structures and galaxy build-up. Using multi-band photometry we studied the intragroup light component (IGL) observed in compact groups of galaxies in a subsample of Hickson's catalogue, an efficient tool for determining its stage of dynamical evolution and for mapping its gravitational potential. Applying the OV WAV package, a wavelet based technique, we can identify the IGL independently of the main contaminating effects. The fractions of IGL detected range from 11% to 46%, with one group with no IGL detected. The colors are consistent with those for old stellar populations and the mean surface brightnesses range from 24.8 to 28.4 B mag arcsec −2 . Using the IGL, along with other dynamical evolution indicators, we could establish an evolutionary sequence for our sample.
The Astrophysical Journal, 1998
We explore the possibility of calibrating massive cluster elliptical galaxies as cosmological sta... more We explore the possibility of calibrating massive cluster elliptical galaxies as cosmological standard rods using the fundamental plane relation combined with a correction for luminosity evolution. Although cluster ellipticals certainly formed in a complex way, their passive evolution out to redshifts of about 1 indicates that basically all major merging and accretion events took place at higher redshifts. Therefore, a calibration of their luminosity evolution can be attempted. We propose to use the Mg-p relation for that purpose because it is independent of distance and cosmology. We discuss a variety of possible caveats, ranging from dynamical evolution to uncertainties in stellar population models and evolution corrections to the presence of age spread. Sources of major random and systematic errors are analyzed as well.
The Astronomical Journal, 2002
We have obtained deep photometry of NGC 1199 (in the compact group HCG 22) and NGC 6868 (in the T... more We have obtained deep photometry of NGC 1199 (in the compact group HCG 22) and NGC 6868 (in the Telescopium loose group) with the Keck II and the VLT-I telescopes. Both galaxies are the optically brightest galaxy of their groups. NGC 1199 has two companion galaxies at a median projected distance of only 33 kpc and, based in its peculiar internal structure and large X-ray halo, NGC 6868 has been proposed to be a merger remnant.
Monthly Notices of the Royal Astronomical Society, 2004
We combine the latest observations of disc galaxy photometry and rotation curves at moderate reds... more We combine the latest observations of disc galaxy photometry and rotation curves at moderate redshift from the FORS Deep Field (FDF) with simple models of chemical enrichment. Our method describes the build-up of the stellar component through infall of gas and allows for gas and metal outflows. In this framework, we keep a minimum number of constraints and we search a large volume of parameter space, looking for the models that best reproduce the photometric observations in the observed redshift range (0.5 < z < 1). We find that star formation efficiency correlates well with v max , so that massive discs are more efficient in the formation of stars and have a smaller spread in stellar ages. This trend presents a break at around v max ∼ 140 km s −1 . Galaxies on either side of this threshold have significantly different age distributions. This break has been already suggested by several authors in connection with the contribution from either gravitational instabilities or supernova-driven turbulence to star formation. The gas infall time-scale and gas outflows also present a correlation with galaxy mass, so that massive discs have shorter infall time-scales and smaller outflow fractions. The model presented in this paper suggests that massive discs have formation histories resembling those of early-type galaxies, with highly efficient and short-lived bursts, in contrast with low-mass discs, which have a more extended star formation history. The ages correlate well with galaxy mass or luminosity, and the predicted gas-phase metallicities are consistent with the observations of local and moderate-redshift galaxies. One option to explain the observed shallow slope of the Tully-Fisher relation at intermediate redshift could be small episodes of star formation in low-mass discs.
Monthly Notices of the Royal Astronomical Society, 2011
We use the semi-analytic model GalICS to predict the Tully-Fisher relation in the B, I and for th... more We use the semi-analytic model GalICS to predict the Tully-Fisher relation in the B, I and for the first time, in the K band, and its evolution with redshift, up to z ∼ 1. We refined the determination of the disk galaxies rotation velocity, with a dynamical recipe for the rotation curve, rather than a simple conversion from the total mass to maximum velocity. The new recipe takes into account the disk shape factor, and the angular momentum transfer occurring during secular evolution leading to the formation of bulges. This produces model rotation velocities that are lower by ∼ 40−50 km/s in case of Milky Way-like objects, up to ∼ 50−60 km/s at the high-mass end, and 20−30 km/s for the majority of the spirals, amounting to an average effect of ∼ 20 − 25%. We implemented stellar population models with a complete treatment of the thermally pulsing asymptotic giant branch, which leads to a revision of the mass-to-light ratio in the near-IR. Due to this effect, K band luminosities increase by ∼ 0.5 mags at redshift z = 0 and by ∼ 1 mags at z = 3, while in the I band at the same redshifts the increase amounts to ∼ 0.3 and ∼ 0.5 mags. With these two new recipes in place, the comparison between the predicted Tully-Fisher relation with a series of datasets in the optical and near-infrared, at redshifts between 0 and 1, is used as a diagnostics of the assembly and evolution of spiral galaxies in the model. The new model shows a net improvement in comparison with its original version of 2003. However, the redshift z = 0 predicted Tully-Fisher is too bright in all bands, although the model is able to reproduce the morphological differentiation observed in the K band. At redshifts z 0.4 the match between the model and data improves dramatically. We argue that this behavior is caused by inadequate star formation histories in the model galaxies at low redshifts. The star-formation rate declines too slowly, due to continuous gas infall that is not efficiently suppressed.
Monthly Notices of the Royal Astronomical Society, 2014
We analyse the extended, ionized-gas emission of 24 early-type galaxies (ETGs) at 0 < z < 1 from ... more We analyse the extended, ionized-gas emission of 24 early-type galaxies (ETGs) at 0 < z < 1 from the ESO Distant Cluster Survey (EDisCS). We discuss different possible sources of ionization and favour star-formation as the main cause of the observed emission. Ten galaxies have disturbed gas kinematics, while 14 have rotating gas disks. In addition, 15 galaxies are in the field, while 9 are in the infall regions of clusters. This implies that, if the gas has an internal origin, this is likely stripped as the galaxies get closer to the cluster centre. If the gas instead comes from an external source, then our results suggest that this is more likely acquired outside the cluster environment, where galaxy-galaxy interactions more commonly take place. We analyse the Tully-Fisher relation of the ETGs with gas disks, and compare them to EDisCS spirals. Taking a matched range of redshifts, M B < −20, and excluding galaxies with large velocity uncertainties, we find that, at fixed rotational velocity, ETGs are 1.7 mag fainter in M B than spirals. At fixed stellar mass, we also find that ETGs have systematically lower specific star-formation rates than spirals. This study constitutes an important step forward towards the understanding of the evolution of the complex ISM in ETGs by significantly extending the look-back-time baseline explored so far.
Monthly Notices of the Royal Astronomical Society, 1998
Using HST WFPC2 V-and R-band data of the z = 0.37 cluster MS1512+36 we show that the z = 2.72 'pr... more Using HST WFPC2 V-and R-band data of the z = 0.37 cluster MS1512+36 we show that the z = 2.72 'protogalaxy' cB58 is not extraordinarily luminous intrinsically but lensed into a gravitational fold arc by the cluster. The arc has a surface brightness weighted axis ratio of 1 : 7, is marginally resolved in width and about 3 ′′ long. Its counterimage was identified and found to be very compact (r 1/2 = 2.4 − 4.0h −1 50 kpc in a q 0 = 0.05 cosmology). In addition, we found three further multiple image systems, one with five and two with three images each. The positions of the multiple images can be explained by modelling the light deflection caused by the cluster and the cDgalaxy with elliptical isothermal potentials. The major axis of the cluster potential approximately agrees with that of the cD-light and that of the X-ray isophotes. Since the multiple images are within ≈ 8 ′′ around the cD galaxy, a cluster core radiuscluster velocity dispersion degeneracy arises. Interpreting the observations conservatively, the cluster velocity dispersion and the core radius are limited to 540 − 670 km/s and 5 ′′ -11 ′′ , respectively, and the brightness of the unlensed counterimage of cB58 is about 23.9 ± 0.3 (R-band), corresponding to a magnification and extinction corrected restframe-B band absolute magnitude of −24.75 ± 0.7 mag. The redshifts of the sources of the remaining three multiple image systems are predicted to be similar to that of cB58 while a strict upper limit of 4 is set as they are visible in B-band ground based data. That part of the source of cB58 which is mapped into the arc is reconstructed and its magnification is found to be µ arc > ∼ 50. This large magnification explains at least some of the untypical spectroscopic properties of cB58, e.g. that the star formation rate seems to be high and uniform and to take place in a large area.
We explore the possibility to calibrate massive cluster ellipticals as cosmological standard rods... more We explore the possibility to calibrate massive cluster ellipticals as cosmological standard rods. The method is based on the Fundamental Plane relation combined with a correction for luminosity evolution which is derived from the Mg-sigma relation. Principle caveats and sources of major errors are briefly discussed. We apply the described procedure to nine elliptical galaxies in two clusters at z=0.375 and derive constraints on the cosmological model. For the best fitting Lambda-free cosmological model we obtain: q_o ~ 0.1, with 90% confidence limits being 0 < q_o < 0.7 (the lower limit being due to the presence of matter in the Universe). If the inflationary scenario applies (i.e., space has flat geometry), then, for the best fitting model, matter and Lambda contribute about equally to the critical cosmic density (i.e. Omega_m ~ Omega_Lambda ~0.5). With 90% confidence Omega_Lambda should be smaller than 0.9. A more detailed account of the work presented here has recently bee...
Arxiv preprint arXiv: …, 2009
Abstract: To understand the processes that build up galaxies we investigate the stellar structure... more Abstract: To understand the processes that build up galaxies we investigate the stellar structure and gas kinematics of spiral and irregular galaxies out to redshift 1. We target 92 galaxies in four cluster (z= 0.3 & 0.5) fields to study the environmental influence. Their ...
The Messenger, 2009
Many large telescopes today offer 3D-spectroscopy and most future facilities (like the European E... more Many large telescopes today offer 3D-spectroscopy and most future facilities (like the European Extremely Large Telescope) will provide such instrument modes. At the VLT, for example, VIMOS and FLAMES offer integral field unit (IFU) spectroscopy in the optical ...
Astronomy and Astrophysics, 2004
We present the redshift evolution of the restframe galaxy luminosity function (LF) in the red r ,... more We present the redshift evolution of the restframe galaxy luminosity function (LF) in the red r , i , and z bands, as derived from the FORS Deep Field (FDF), thus extending our earlier results to longer wavelengths. Using the deep and homogeneous I-band selected dataset of the FDF, we were able to follow the red LFs over the redshift range 0.5 < z < 3.5. The results are based on photometric redshifts for 5558 galaxies derived from the photometry in 9 filters and achieving an accuracy of ∆z/(z spec + 1) ≤ 0.03 with only ∼1% outliers. A comparison with results from the literature shows the reliability of the derived LFs. Because of the depth of the FDF, we can give relatively tight constraints on the faint-end slope α of the LF; the faint-end of the red LFs does not show a large redshift evolution and is compatible within 1σ to 2σ with a constant slope over the redshift range 0.5 < ∼ z < ∼ 2.0. Moreover, the slopes in r , i , and z are very similar to a best-fitting value of α = −1.33 ± 0.03 for the combined bands. There is a clear trend of α to steepen with increasing wavelength: α UV&u = −1.07 ± 0.04 → α g &B = −1.25 ± 0.03 → α r &i &z = −1.33 ± 0.03. We subdivided our galaxy sample into four SED types and determined the contribution of a typical SED type to the overall LF. We show that the wavelength dependence of the LF slope can be explained by the relative contribution of different SED-type LFs to the overall LF, as different SED types dominate the LF in the blue and red bands. Furthermore we also derived and analyzed the luminosity density evolution of the different SED types up to z ∼ 2. We investigated the evolution of M * and φ * by means of the redshift parametrization M * (z) = M * 0 + a ln (1 + z) and φ * (z) = φ * 0 (1 + z) b . Based on the FDF data, we found only a mild brightening of M * (a r ∼ −0.8, and a i ,z ∼ −0.4) and a decreasing φ * (b r ,i ,z ∼ −0.6) with increasing redshift. Therefore, from z ∼ 0.5 to z ∼ 3 the characteristic luminosity increases by ∼0.8, ∼0.4, and ∼0.4 mag in the r , i , and z bands, respectively. Simultaneously the characteristic density decreases by about 40% in all analyzed wavebands. A comparison of the LFs with semianalytical galaxy formation models by shows a similar result to the blue bands: the semi-analytical models predict LFs that describe the data at low redshift very well, but show growing disagreement with increasing redshifts.
We analyse the Tully-Fisher relation at moderate redshift from the point of view of the underlyin... more We analyse the Tully-Fisher relation at moderate redshift from the point of view of the underlying stellar populations, by comparing optical and NIR photometry with a phenomenological model that combines population synthesis with a simple prescription for chemical enrichment. The sample comprises 108 late-type galaxies extracted from the FORS Deep Field (FDF) and William Herschel Deep Field (WHDF) surveys at z < ∼ 1 (median redshift z=0.45). A correlation is found between stellar mass and the parameters that describe the star formation history, with massive galaxies forming their populations early (z FOR ∼ 3), with star formation timescales, τ 1 ∼ 4 Gyr; although with very efficient chemical enrichment timescales (τ 2 ∼ 1 Gyr). In contrast, the stellar-to-dynamical mass ratio -which, in principle, would track the efficiency of feedback in the baryonic processes driving galaxy formation -does not appear to correlate with the model parameters. On the Tully-Fisher plane, no significant age segregation is found at fixed circular speed, whereas at fixed stellar-to-dynamical mass fraction, age splits the sample, with older galaxies having faster circular speeds at fixed M s /M dyn . Although our model does not introduce any prior constraint on dust reddening, we obtain a strong correlation between colour excess and stellar mass.
The formation of ultra-compact dwarf galaxies (UCDs) is believed to be interaction driven, and UC... more The formation of ultra-compact dwarf galaxies (UCDs) is believed to be interaction driven, and UCDs are abundant in the cores of galaxy clusters, environments that mark the end-point of galaxy evolution. Nothing is known about the properties of UCDs in compact groups of galaxies, environments where most of galaxy evolution and interaction is believed to occur and where UCDs in intermediate state of evolution may be expected. The main goal of this study is to detect and characterize, for the first time, the UCD population of compact groups. For that, 2 groups in different evolutionary stages, HCG 22 and HCG 90, were targeted with VLT/FORS2/MXU. We detect 16 and 5 objects belonging to HCG 22 and HCG 90, respectively, covering the magnitude range -10.0 > M_R > -11.5 mag. Their colours are consistent with old ages covering a broad range in metallicities. Photometric mass estimates put 4 objects in HCG 90 and 9 in HCG 22 in the mass range of UCDs (>2x10^6 M_Sun) for an assumed a...
Astronomy & Astrophysics, 2014
We describe and discuss the selection procedure and statistical properties of the galaxy sample u... more We describe and discuss the selection procedure and statistical properties of the galaxy sample used by the Calar Alto Legacy Integral Field Area Survey (CALIFA), a public legacy survey of 600 galaxies using integral field spectroscopy. The CALIFA 'mother sample' was selected from the Sloan Digital Sky Survey (SDSS) DR7 photometric catalogue to include all galaxies with an r-band isophotal major axis between 45 and 79.2 and with a redshift 0.005 < z < 0.03. The mother sample contains 939 objects, 600 of which will be observed in the course of the CALIFA survey. The selection of targets for observations is based solely on visibility and thus keeps the statistical properties of the mother sample. By comparison with a large set of SDSS galaxies, we find that the CALIFA sample is representative of galaxies over a luminosity range of −19 > Mr > −23.1 and over a stellar mass range between 10 9.7 and 10 11.4 M . In particular, within these ranges, the diameter selection does not lead to any significant bias against -or in favour of -intrinsically large or small galaxies. Only below luminosities of Mr = −19 (or stellar masses < 10 9.7 M ) is there a prevalence of galaxies with larger isophotal sizes, especially of nearly edge-on late-type galaxies, but such galaxies form < 10% of the full sample. We estimate volume-corrected distribution functions in luminosities and sizes and show that these are statistically fully compatible with estimates from the full SDSS when accounting for large-scale structure. For full characterization of the sample, we also present a number of value-added quantities determined for the galaxies in the CALIFA sample. These include consistent multi-band photometry based on growth curve analyses; stellar masses; distances and quantities derived from these; morphological classifications; and an overview of available multi-wavelength photometric measurements. We also explore different ways of characterizing the environments of CALIFA galaxies, finding that the sample covers environmental conditions from the field to genuine clusters. We finally consider the expected incidence of active galactic nuclei among CALIFA galaxies given the existing pre-CALIFA data, finding that the final observed CALIFA sample will contain approximately 30 Sey2 galaxies.
Our spectroscopic observations were spread across 5 nights in October and November 2004 for Cl 04... more Our spectroscopic observations were spread across 5 nights in October and November 2004 for Cl 0412, 7 nights in December 2005 and February 2005 for MS 1008, 5 nights between May and July 2005 for MS 2137. For photometric data, we use both VLT/FORS2 and HST/ACS images. We obtained imaging of the MS 1008, MS 2137 and Cl 0412 samples in the ACS/F606W filter while we exploited existing imaging of MS 0451 in the ACS/F814W filter from the ST-ECF HST archive. Ground based images were taken in the B, V, R and I filters for the whole sample. The FORS2 filters B, V and I are close approximations to the Johnson-Cousins photometric system while the R filter is a special filter for FORS2 that is similar to the Cousins R . (5 data files).
Proceedings of the International Astronomical Union, 2006
Most of the galaxies in the local universe are located in groups, in particular in small groups, ... more Most of the galaxies in the local universe are located in groups, in particular in small groups, and most of the transformations suffered by galaxies located in today's clusters are likely to have occurred in groups at higher redshifts. Understanding the formation and evolution of groups is essential to understand the whole picture of structures and galaxy build-up. Using multi-band photometry we studied the intragroup light component (IGL) observed in compact groups of galaxies in a subsample of Hickson's catalogue, an efficient tool for determining its stage of dynamical evolution and for mapping its gravitational potential. Applying the OV WAV package, a wavelet based technique, we can identify the IGL independently of the main contaminating effects. The fractions of IGL detected range from 11% to 46%, with one group with no IGL detected. The colors are consistent with those for old stellar populations and the mean surface brightnesses range from 24.8 to 28.4 B mag arcsec −2 . Using the IGL, along with other dynamical evolution indicators, we could establish an evolutionary sequence for our sample.
The Astrophysical Journal, 1998
We explore the possibility of calibrating massive cluster elliptical galaxies as cosmological sta... more We explore the possibility of calibrating massive cluster elliptical galaxies as cosmological standard rods using the fundamental plane relation combined with a correction for luminosity evolution. Although cluster ellipticals certainly formed in a complex way, their passive evolution out to redshifts of about 1 indicates that basically all major merging and accretion events took place at higher redshifts. Therefore, a calibration of their luminosity evolution can be attempted. We propose to use the Mg-p relation for that purpose because it is independent of distance and cosmology. We discuss a variety of possible caveats, ranging from dynamical evolution to uncertainties in stellar population models and evolution corrections to the presence of age spread. Sources of major random and systematic errors are analyzed as well.
The Astronomical Journal, 2002
We have obtained deep photometry of NGC 1199 (in the compact group HCG 22) and NGC 6868 (in the T... more We have obtained deep photometry of NGC 1199 (in the compact group HCG 22) and NGC 6868 (in the Telescopium loose group) with the Keck II and the VLT-I telescopes. Both galaxies are the optically brightest galaxy of their groups. NGC 1199 has two companion galaxies at a median projected distance of only 33 kpc and, based in its peculiar internal structure and large X-ray halo, NGC 6868 has been proposed to be a merger remnant.
Monthly Notices of the Royal Astronomical Society, 2004
We combine the latest observations of disc galaxy photometry and rotation curves at moderate reds... more We combine the latest observations of disc galaxy photometry and rotation curves at moderate redshift from the FORS Deep Field (FDF) with simple models of chemical enrichment. Our method describes the build-up of the stellar component through infall of gas and allows for gas and metal outflows. In this framework, we keep a minimum number of constraints and we search a large volume of parameter space, looking for the models that best reproduce the photometric observations in the observed redshift range (0.5 < z < 1). We find that star formation efficiency correlates well with v max , so that massive discs are more efficient in the formation of stars and have a smaller spread in stellar ages. This trend presents a break at around v max ∼ 140 km s −1 . Galaxies on either side of this threshold have significantly different age distributions. This break has been already suggested by several authors in connection with the contribution from either gravitational instabilities or supernova-driven turbulence to star formation. The gas infall time-scale and gas outflows also present a correlation with galaxy mass, so that massive discs have shorter infall time-scales and smaller outflow fractions. The model presented in this paper suggests that massive discs have formation histories resembling those of early-type galaxies, with highly efficient and short-lived bursts, in contrast with low-mass discs, which have a more extended star formation history. The ages correlate well with galaxy mass or luminosity, and the predicted gas-phase metallicities are consistent with the observations of local and moderate-redshift galaxies. One option to explain the observed shallow slope of the Tully-Fisher relation at intermediate redshift could be small episodes of star formation in low-mass discs.
Monthly Notices of the Royal Astronomical Society, 2011
We use the semi-analytic model GalICS to predict the Tully-Fisher relation in the B, I and for th... more We use the semi-analytic model GalICS to predict the Tully-Fisher relation in the B, I and for the first time, in the K band, and its evolution with redshift, up to z ∼ 1. We refined the determination of the disk galaxies rotation velocity, with a dynamical recipe for the rotation curve, rather than a simple conversion from the total mass to maximum velocity. The new recipe takes into account the disk shape factor, and the angular momentum transfer occurring during secular evolution leading to the formation of bulges. This produces model rotation velocities that are lower by ∼ 40−50 km/s in case of Milky Way-like objects, up to ∼ 50−60 km/s at the high-mass end, and 20−30 km/s for the majority of the spirals, amounting to an average effect of ∼ 20 − 25%. We implemented stellar population models with a complete treatment of the thermally pulsing asymptotic giant branch, which leads to a revision of the mass-to-light ratio in the near-IR. Due to this effect, K band luminosities increase by ∼ 0.5 mags at redshift z = 0 and by ∼ 1 mags at z = 3, while in the I band at the same redshifts the increase amounts to ∼ 0.3 and ∼ 0.5 mags. With these two new recipes in place, the comparison between the predicted Tully-Fisher relation with a series of datasets in the optical and near-infrared, at redshifts between 0 and 1, is used as a diagnostics of the assembly and evolution of spiral galaxies in the model. The new model shows a net improvement in comparison with its original version of 2003. However, the redshift z = 0 predicted Tully-Fisher is too bright in all bands, although the model is able to reproduce the morphological differentiation observed in the K band. At redshifts z 0.4 the match between the model and data improves dramatically. We argue that this behavior is caused by inadequate star formation histories in the model galaxies at low redshifts. The star-formation rate declines too slowly, due to continuous gas infall that is not efficiently suppressed.
Monthly Notices of the Royal Astronomical Society, 2014
We analyse the extended, ionized-gas emission of 24 early-type galaxies (ETGs) at 0 < z < 1 from ... more We analyse the extended, ionized-gas emission of 24 early-type galaxies (ETGs) at 0 < z < 1 from the ESO Distant Cluster Survey (EDisCS). We discuss different possible sources of ionization and favour star-formation as the main cause of the observed emission. Ten galaxies have disturbed gas kinematics, while 14 have rotating gas disks. In addition, 15 galaxies are in the field, while 9 are in the infall regions of clusters. This implies that, if the gas has an internal origin, this is likely stripped as the galaxies get closer to the cluster centre. If the gas instead comes from an external source, then our results suggest that this is more likely acquired outside the cluster environment, where galaxy-galaxy interactions more commonly take place. We analyse the Tully-Fisher relation of the ETGs with gas disks, and compare them to EDisCS spirals. Taking a matched range of redshifts, M B < −20, and excluding galaxies with large velocity uncertainties, we find that, at fixed rotational velocity, ETGs are 1.7 mag fainter in M B than spirals. At fixed stellar mass, we also find that ETGs have systematically lower specific star-formation rates than spirals. This study constitutes an important step forward towards the understanding of the evolution of the complex ISM in ETGs by significantly extending the look-back-time baseline explored so far.
Monthly Notices of the Royal Astronomical Society, 1998
Using HST WFPC2 V-and R-band data of the z = 0.37 cluster MS1512+36 we show that the z = 2.72 'pr... more Using HST WFPC2 V-and R-band data of the z = 0.37 cluster MS1512+36 we show that the z = 2.72 'protogalaxy' cB58 is not extraordinarily luminous intrinsically but lensed into a gravitational fold arc by the cluster. The arc has a surface brightness weighted axis ratio of 1 : 7, is marginally resolved in width and about 3 ′′ long. Its counterimage was identified and found to be very compact (r 1/2 = 2.4 − 4.0h −1 50 kpc in a q 0 = 0.05 cosmology). In addition, we found three further multiple image systems, one with five and two with three images each. The positions of the multiple images can be explained by modelling the light deflection caused by the cluster and the cDgalaxy with elliptical isothermal potentials. The major axis of the cluster potential approximately agrees with that of the cD-light and that of the X-ray isophotes. Since the multiple images are within ≈ 8 ′′ around the cD galaxy, a cluster core radiuscluster velocity dispersion degeneracy arises. Interpreting the observations conservatively, the cluster velocity dispersion and the core radius are limited to 540 − 670 km/s and 5 ′′ -11 ′′ , respectively, and the brightness of the unlensed counterimage of cB58 is about 23.9 ± 0.3 (R-band), corresponding to a magnification and extinction corrected restframe-B band absolute magnitude of −24.75 ± 0.7 mag. The redshifts of the sources of the remaining three multiple image systems are predicted to be similar to that of cB58 while a strict upper limit of 4 is set as they are visible in B-band ground based data. That part of the source of cB58 which is mapped into the arc is reconstructed and its magnification is found to be µ arc > ∼ 50. This large magnification explains at least some of the untypical spectroscopic properties of cB58, e.g. that the star formation rate seems to be high and uniform and to take place in a large area.
We explore the possibility to calibrate massive cluster ellipticals as cosmological standard rods... more We explore the possibility to calibrate massive cluster ellipticals as cosmological standard rods. The method is based on the Fundamental Plane relation combined with a correction for luminosity evolution which is derived from the Mg-sigma relation. Principle caveats and sources of major errors are briefly discussed. We apply the described procedure to nine elliptical galaxies in two clusters at z=0.375 and derive constraints on the cosmological model. For the best fitting Lambda-free cosmological model we obtain: q_o ~ 0.1, with 90% confidence limits being 0 < q_o < 0.7 (the lower limit being due to the presence of matter in the Universe). If the inflationary scenario applies (i.e., space has flat geometry), then, for the best fitting model, matter and Lambda contribute about equally to the critical cosmic density (i.e. Omega_m ~ Omega_Lambda ~0.5). With 90% confidence Omega_Lambda should be smaller than 0.9. A more detailed account of the work presented here has recently bee...
Arxiv preprint arXiv: …, 2009
Abstract: To understand the processes that build up galaxies we investigate the stellar structure... more Abstract: To understand the processes that build up galaxies we investigate the stellar structure and gas kinematics of spiral and irregular galaxies out to redshift 1. We target 92 galaxies in four cluster (z= 0.3 & 0.5) fields to study the environmental influence. Their ...
The Messenger, 2009
Many large telescopes today offer 3D-spectroscopy and most future facilities (like the European E... more Many large telescopes today offer 3D-spectroscopy and most future facilities (like the European Extremely Large Telescope) will provide such instrument modes. At the VLT, for example, VIMOS and FLAMES offer integral field unit (IFU) spectroscopy in the optical ...
Astronomy and Astrophysics, 2004
We present the redshift evolution of the restframe galaxy luminosity function (LF) in the red r ,... more We present the redshift evolution of the restframe galaxy luminosity function (LF) in the red r , i , and z bands, as derived from the FORS Deep Field (FDF), thus extending our earlier results to longer wavelengths. Using the deep and homogeneous I-band selected dataset of the FDF, we were able to follow the red LFs over the redshift range 0.5 < z < 3.5. The results are based on photometric redshifts for 5558 galaxies derived from the photometry in 9 filters and achieving an accuracy of ∆z/(z spec + 1) ≤ 0.03 with only ∼1% outliers. A comparison with results from the literature shows the reliability of the derived LFs. Because of the depth of the FDF, we can give relatively tight constraints on the faint-end slope α of the LF; the faint-end of the red LFs does not show a large redshift evolution and is compatible within 1σ to 2σ with a constant slope over the redshift range 0.5 < ∼ z < ∼ 2.0. Moreover, the slopes in r , i , and z are very similar to a best-fitting value of α = −1.33 ± 0.03 for the combined bands. There is a clear trend of α to steepen with increasing wavelength: α UV&u = −1.07 ± 0.04 → α g &B = −1.25 ± 0.03 → α r &i &z = −1.33 ± 0.03. We subdivided our galaxy sample into four SED types and determined the contribution of a typical SED type to the overall LF. We show that the wavelength dependence of the LF slope can be explained by the relative contribution of different SED-type LFs to the overall LF, as different SED types dominate the LF in the blue and red bands. Furthermore we also derived and analyzed the luminosity density evolution of the different SED types up to z ∼ 2. We investigated the evolution of M * and φ * by means of the redshift parametrization M * (z) = M * 0 + a ln (1 + z) and φ * (z) = φ * 0 (1 + z) b . Based on the FDF data, we found only a mild brightening of M * (a r ∼ −0.8, and a i ,z ∼ −0.4) and a decreasing φ * (b r ,i ,z ∼ −0.6) with increasing redshift. Therefore, from z ∼ 0.5 to z ∼ 3 the characteristic luminosity increases by ∼0.8, ∼0.4, and ∼0.4 mag in the r , i , and z bands, respectively. Simultaneously the characteristic density decreases by about 40% in all analyzed wavebands. A comparison of the LFs with semianalytical galaxy formation models by shows a similar result to the blue bands: the semi-analytical models predict LFs that describe the data at low redshift very well, but show growing disagreement with increasing redshifts.
We analyse the Tully-Fisher relation at moderate redshift from the point of view of the underlyin... more We analyse the Tully-Fisher relation at moderate redshift from the point of view of the underlying stellar populations, by comparing optical and NIR photometry with a phenomenological model that combines population synthesis with a simple prescription for chemical enrichment. The sample comprises 108 late-type galaxies extracted from the FORS Deep Field (FDF) and William Herschel Deep Field (WHDF) surveys at z < ∼ 1 (median redshift z=0.45). A correlation is found between stellar mass and the parameters that describe the star formation history, with massive galaxies forming their populations early (z FOR ∼ 3), with star formation timescales, τ 1 ∼ 4 Gyr; although with very efficient chemical enrichment timescales (τ 2 ∼ 1 Gyr). In contrast, the stellar-to-dynamical mass ratio -which, in principle, would track the efficiency of feedback in the baryonic processes driving galaxy formation -does not appear to correlate with the model parameters. On the Tully-Fisher plane, no significant age segregation is found at fixed circular speed, whereas at fixed stellar-to-dynamical mass fraction, age splits the sample, with older galaxies having faster circular speeds at fixed M s /M dyn . Although our model does not introduce any prior constraint on dust reddening, we obtain a strong correlation between colour excess and stellar mass.
The formation of ultra-compact dwarf galaxies (UCDs) is believed to be interaction driven, and UC... more The formation of ultra-compact dwarf galaxies (UCDs) is believed to be interaction driven, and UCDs are abundant in the cores of galaxy clusters, environments that mark the end-point of galaxy evolution. Nothing is known about the properties of UCDs in compact groups of galaxies, environments where most of galaxy evolution and interaction is believed to occur and where UCDs in intermediate state of evolution may be expected. The main goal of this study is to detect and characterize, for the first time, the UCD population of compact groups. For that, 2 groups in different evolutionary stages, HCG 22 and HCG 90, were targeted with VLT/FORS2/MXU. We detect 16 and 5 objects belonging to HCG 22 and HCG 90, respectively, covering the magnitude range -10.0 > M_R > -11.5 mag. Their colours are consistent with old ages covering a broad range in metallicities. Photometric mass estimates put 4 objects in HCG 90 and 9 in HCG 22 in the mass range of UCDs (>2x10^6 M_Sun) for an assumed a...