Author Index

Authors Index

Author Index     

A multi-wavelength study of the evolution of early-type galaxies in groups: the ultraviolet view

The ultraviolet–optical colour magnitude diagram of rich galaxy groups is characterised by a well developed Red Sequence, a Blue Cloud and the so-called Green Valley. Loose, less evolved groups of galaxies which are probably not virialised yet may lack a well defined Red Sequence. This is actually explained in the framework of galaxy evolution. We are focussing on understanding galaxy migration towards the Red Sequence, checking for signatures of such a transition in their photometric and morphological properties. We report on the ultraviolet properties of a sample of early-type (ellipticals+S0s) galaxies inhabiting the Red Sequence. The analysis of their structures, as derived by fitting a Sérsic law to their ultraviolet luminosity profiles, suggests the presence of an underlying disk. This is the hallmark of dissipation processes that still must have a role to play in the evolution of this class of galaxies. Smooth particle hydrodynamic simulations with chemo-photometric implementations able to match the global properties of our targets are used to derive their evolutionary paths through ultraviolet–optical colour magnitude diagrams, providing some fundamental information such as the crossing time through the Green Valley, which depends on their luminosity. The transition from the Blue Cloud to the Red Sequence takes several Gyrs, being about 3–5 Gyr for the brightest galaxies and longer for fainter ones, if occurring.The photometric study of nearby galaxy structures in the ultraviolet is seriously hampered by either the limited field of view of the cameras (e.g., in Hubble Space Telescope) or by the low spatial resolution of the images (e.g., in the Galaxy Evolution Explorer). Current missions equipped with telescopes and cameras sensitive to ultraviolet wavelengths, such as Swift-UVOT and Astrosat-UVIT, provide a relatively large field of view and a better resolution than the Galaxy Evolution Explorer. More powerful ultraviolet instruments (size, resolution and field of view) are obviously bound to yield fundamental advances in the accuracy and depth of the surface photometry and in the characterisation of the galaxy environment.     

Engineering geomorphological interpretation of the Mitchell Creek Landslide,British Columbia,Canada

The recent assessment of the Mitchell Creek Landslide (MCL) in northern British Columbia is a good case history of engineering geomorphological analysis of a large landslide. It was completed using historic aerial photographs, with approximately 20-year time intervals dating back to the mid-twentieth century and field investigations completed between 2008 and 2014. The large bedrock slide initiated between 1956 and 1972 and continues to experience ongoing annual movements. Significant glacial downwasting and retreat has been observed in the photographic record, and it is hypothesized that alpine glaciation has contributed to development of the MCL. This paper documents four aspects of the engineering geomorphological assessment completed at the MCL: (i) topographic evolution, (ii) slope morphology, (iii) deformation features, and (iv) displacement behavior. Four distinct geomorphic zones have been defined at the MCL based on these analyses, controlled by different failure mechanisms. The extents of these zones have changed little over the documented history of the landslide, and rates of movement estimated from aerial photography have been consistent over the last 60 years. Retreat of the Mitchell Valley Glacier appears to have played an important role in landslide initiation, as the ice mass receded the kinematic freedom of the slope increased. This study of the initiation and development of the MCL demonstrates the capabilities of a multi-faceted approach to engineering geomorphology. The combination of historical aerial photographs with digital photogrammetric modeling and point cloud analysis techniques, and geomorphological mapping, allows for development of a robust understanding of landslide behavior.     

Drought 2002 in Colorado: An Unprecedented Drought or a Routine Drought?

The 2002 drought in Colorado was reported by the media and by public figures, and even by a national drought-monitoring agency, as an exceptionally severe drought. In this paper we examine evidence for this claim. Our study shows that, while the impacts of water shortages were exceptional everywhere, the observed precipitation deficit was less than extreme over a good fraction of the state. A likely explanation of this discrepancy is the imbalance between water supply and water demand over time. For a given level of water supply, water shortages become intensified as water demands increase over time. The sobering conclusion is that Colorado is more vulnerable to drought today than under similar precipitation deficits in the past.     

Impact of land cover data on the simulation of urban heat island for Berlin using WRF coupled with bulk approach of Noah-LSM

Urban-rural difference of land cover is the key determinant of urban heat island (UHI). In order to evaluate the impact of land cover data on the simulation of UHI, a comparative study between up-to-date CORINE land cover (CLC) and Urban Atlas (UA) with fine resolution (100 and 10 m) and old US Geological Survey (USGS) data with coarse resolution (30 s) was conducted using the Weather Research and Forecasting model (WRF) coupled with bulk approach of Noah-LSM for Berlin. The comparison between old data and new data partly reveals the effect of urbanization on UHI and the historical evolution of UHI, while the comparison between different resolution data reveals the impact of resolution of land cover on the simulation of UHI. Given the high heterogeneity of urban surface and the fine-resolution land cover data, the mosaic approach was implemented in this study to calculate the sub-grid variability in land cover compositions. Results showed that the simulations using UA and CLC data perform better than that using USGS data for both air and land surface temperatures. USGS-based simulation underestimates the temperature, especially in rural areas. The longitudinal variations of both temperature and land surface temperature show good agreement with urban fraction for all the three simulations. To better study the comprehensive characteristic of UHI over Berlin, the UHI curves (UHIC) are developed for all the three simulations based on the relationship between temperature and urban fraction. CLC- and UA-based simulations show smoother UHICs than USGS-based simulation. The simulation with old USGS data obviously underestimates the extent of UHI, while the up-to-date CLC and UA data better reflect the real urbanization and simulate the spatial distribution of UHI more accurately. However, the intensity of UHI simulated by CLC and UA data is not higher than that simulated by USGS data. The simulated air temperature is not dominated by the land cover as much as the land surface temperature, as air temperature is also affected by air advection.     

BeppoSAX observations of 1-Jy BL Lacertae objects – I

We present new BeppoSAX observations of seven BL Lacertae objects selected from the 1-Jy sample plus one additional source. The collected data cover the energy range     (observer's frame), reaching ∼50 keV for one source (BL Lac). All sources characterized by a peak in their multifrequency spectra at infrared/optical energies (i.e., of the low-energy peaked BL Lac type, LBL) display a relatively flat     X-ray spectrum, which we interpret as inverse Compton emission. Four objects (two-thirds of the LBLs) show some evidence for a low-energy steepening, which is probably due to the synchrotron tail merging into the inverse Compton component around ∼     . If this were generally the case with LBLs, it would explain why the     ROSAT spectra of our sources are systematically steeper than the BeppoSAX ones     . The broad-band spectral energy distributions fully confirm this picture, and a synchrotron inverse Compton model allows us to derive the physical parameters (intrinsic power, magnetic field, etc.) of our sources. Combining our results with those obtained by BeppoSAX on BL Lacs covering a wide range of synchrotron peak frequency, ν _peak, we confirm and clarify the dependence of the X-ray spectral index on ν _peak originally found in ROSAT data.     

TIGRE: A new robotic spectroscopy telescope at Guanajuato,Mexico

TIGRE is a new robotic spectroscopy telescope located in central Mexico at the La Luz Observatory of the University of Guanajuato. The 1.2 m telescope is fiber‐coupled to an ´echelle spectrograph with a spectral resolving power exceeding 20000 over most of the covered spectral range between 3800 Å and 8800 Å, with a small gap of 130 Å around 5800 Å. TIGRE operates robotically, i.e. it (normally) carries out all observations without any human intervention, including, in particular, the target selection in any given observing night. In this paper we describe the properties of the TIGRE instrumentation and its technical realization, as well as our first operational experience with the performance and efficiency of the overall system. Finally, we present some examples of recent TIGRE observations. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)