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Groundwater plays an important role in New Zealand water supplies and hence monitoring activities are conducted regularly. Most monitoring programmes aim to evaluate groundwater chemistry and almost completely overlook the microbial component in this ecosystem. In our present study, the bacterial community structure of groundwater in the Wairarapa Valley was examined using the terminal restriction fragment length polymorphism (T-RFLP), and relationships between bacterial community structure and groundwater chemistry, aquifer confinement and groundwater usage were explored. In addition, the results from this study were compared with a previous T-RFLP survey of the same area in an attempt to detect changes in bacterial community structure over time. The data obtained suggested that bacterial community structure was related to groundwater chemistry, especially to redox conditions. Species composition showed minimal variation over time if groundwater chemistry remained unchanged. These findings reflect the potential of using bacterial communities as biological indicators to evaluate the health of groundwater ecosystems. We suggest that it is important to include this type of broad bacterial diversity assessment criteria into regular groundwater monitoring activities. 相似文献
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K.G. Noeske J. Iglesias-Páramo J.M. Vílchez K.J. Fricke 《Astrophysics and Space Science》2001,276(2-4):577-583
We are currently performing a new analysis of the close environment of star-forming dwarf galaxies and its effects on their
star-forming activity. For a sample of 142 thoroughly studied objects, we search the NASA Extragalactic Database for possible
companion galaxies of any apparent luminosity and angular size. From a first analysis of a part of our sample, we find only
about 50% of our objects to be isolated in the sense that no companion object was detected within a redshift difference of
500 km s-1 and an angular separation corresponding to a projected distance of 1 Mpc, assuming H
0=75km s-1 Mpc-1. By splitting the sample into different redshift intervals, we demonstrate an observational bias against low-luminosity companion
objects which implies that a large fraction of star-forming dwarf galaxies, although lacking bright companions, might possess
dwarf companion objects. Similarly to other authors, we find no evidence for a difference in star-forming activity due to
the presence or absence of possible companions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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准噶尔盆地南缘新生代构造特征及其与砂岩型铀矿成矿作用初析 总被引：5，自引：0，他引：5
准噶尔盆地南缘盆山结合部中新生界沉积巨厚,新生代变形强烈,是研究新盆山耦合的理想场所,也是我国砂岩型铀矿找矿的远景区段。本文在综合前人资料和野外观测分析基础上,根据新生代构造活动特征,将准噶尔盆地南缘划分为博格达山前和西部断褶带两个构造分区,博格达山前以强烈的逆冲推覆为特征,发育多条活动的逆冲推覆断裂; 乌鲁木齐以西至乌苏南的西部断褶带则发育三-四排的褶皱-逆冲断裂构造带。对采自博格达山前逆冲推覆断裂带内的方解石和断层泥,利用电子自旋共振测年手段,推测博格达山前的富康-吉木萨尔断裂带和北三台断裂带分别在0.7~1Ma和0.25Ma期间,经历了一期重要的逆冲推覆作用。结合盆地南缘砂岩型铀矿的展布规律及其成矿条件的分析,探讨了新生代构造运动对砂岩型铀矿成矿的控制作用,认为西部断褶带的第一排构造带具有较好的成矿前景,而博格达山前由于新生代构造活动强烈而相对成矿不利,为此提出了准噶尔盆地南缘砂岩型铀矿成矿“构造优先权”的构造控矿模式,进而指出了区域找矿的优选区段。 相似文献
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P. Papaderos Y.I. Izotov K.G. Noeske L.M. Cairós N.G. Guseva T.X. Thuan K.J. Fricke 《Astrophysics and Space Science》2003,284(2):619-622
Using HST and ground-based optical and NIR imaging data, we investigate whether the blue compact dwarf (BCD) galaxy I Zw 18
possesses an extended low-surface brightness (LSB) old stellar population underlying its star-forming (SF) regions. We show
that the exponential intensity decrease observed in the filamentary LSB envelope of the BCD out to 18″ (1.3 kpc at the adopted
distance of 15 Mpc) is not due to an evolved stellar disc, but rather due to extended ionized gas emission. Broad-band images
reveal, after subtraction of nebular line emission, a compact stellar LSB component extending slightly beyond the SF regions.
This stellar host, being blue over a radius range of 5 exponential scale lengths and showing little colour contrast to the
SF component, differs strikingly from the red LSB host of standard BCDs. This fact, in connection with the blue colours of
component I Zw 18 C (see discussion in Papaderos et al. 2002), suggests that most of the stellar mass in I Zw 18 has formed
within the last 0.5 Gyr. Furthermore, we show that the exponential intensity fall-off in the filamentary ionized envelope
of I Zw 18 is not particular to this system but a common property of the ionized halo of many SF dwarf galaxies on galactocentric
distances of several kpc. In the absence of an appreciable underlying stellar background, extended ionized gas emission dominates
in the periphery of I Zw 18, superficially resembling an exponential stellar disc on optical surface brightness profiles.
The case of I Zw 18 suggests caution in the search of more distant young galaxy candidates. Intense SF activity in the early
phase of dwarf galaxy formation may result in an extended ionized gas halo which can be mistaken for an evolved stellar disc
by studying only its exponential surface brightness profile.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Michael C. Cooper Jeffrey A. Newman Benjamin J. Weiner Renbin Yan Christopher N. A. Willmer Kevin Bundy Alison L. Coil † Christopher J. Conselice Marc Davis S. M. Faber Brian F. Gerke Puragra Guhathakurta David C. Koo Kai G. Noeske 《Monthly notices of the Royal Astronomical Society》2008,383(3):1058-1078
Using galaxy samples drawn from the Sloan Digital Sky Survey and the DEEP2 Galaxy Redshift Survey, we study the relationship between star formation and environment at z ∼ 0.1 and 1. We estimate the total star formation rate (SFR) and specific star formation rate (sSFR) for each galaxy according to the measured [O ii ]λ 3727 Å nebular line luminosity, corrected using empirical calibrations to match more robust SFR indicators. Echoing previous results, we find that in the local Universe star formation depends on environment such that galaxies in regions of higher overdensity, on average, have lower SFRs and longer star formation time-scales than their counterparts in lower density regions. At z ∼ 1 , we show that the relationship between sSFR and environment mirrors that found locally. However, we discover that the relationship between total SFR and overdensity at z ∼ 1 is inverted relative to the local relation. This observed evolution in the SFR–density relation is driven, in part, by a population of bright, blue galaxies in dense environments at z ∼ 1 . This population, which lacks a counterpart at z ∼ 0 , is thought to evolve into members of the red sequence from z ∼ 1 to ∼0. Finally, we conclude that environment does not play a dominant role in the cosmic star formation history at z < 1 : the dependence of the mean galaxy SFR on local galaxy density at constant redshift is small compared to the decline in the global SFR space density over the last 7 Gyr. 相似文献
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L.M. Cairós B. GarcÍa-Lorenzo N. Caon J.M. VÍlchez P. Papaderos K. Noeske 《Astrophysics and Space Science》2003,284(2):611-614
Preliminary results from a detailed spectrophotometric analysis of the blue compact dwarf galaxy (BCD) Mrk 35 are presented.
We have performed deep UBVRI broad-band and Hα narrow-band optical observations, near-infrared (JHK
s) imaging and long-slit spectroscopy of the galaxy. Mrk 35 is composed of a very young starburst population distributed in
a bar-like structure, placed on top of an underlying, older stellar host galaxy. Using predictions of evolutionary synthesis
models, we estimate the ages of both the starburst regions and the underlying stellar component.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
K.G. Noeske L.M. Cairós P. Papaderos J.M. Vílchez K.J. Fricke 《Astrophysics and Space Science》2001,276(2-4):901-908
We are currently analysing image data for a large sample of blue compact dwarf galaxies (BCDs), obtained in multiple optical
broad- and narrow-band filters. We present preliminary results of a multi-band analysis of two typical BCDs, Mrk 5 and I Zw
123, for which surface-brightness profiles, colour profiles, colour maps and Hα equivalent-width maps have been derived. We demonstrate how a combination of these different processing methods allows a
separate analysis of the young and old stellar populations with respect to their colours and spatial distributions. By comparing
the derived colours with the predictions of evolutionary synthesis models, we estimate ages of the distinct stellar populations.
The surface-brightness profiles of Mrk 5 show an exponential decay at large photometric radii, with slopes typically found
for BCDs. In the case of the very compact object I Zw 123, the surface-brightness profile of the underlying stellar component
can be described either by an exponential or an R
1/4 law. We discuss briefly how noise effects can influence the intrinsic slope of surface brightness profiles at low surface-brightness
levels. For compact objects with extended starbursts, the study of the underlying stellar population can thereby be rendered
difficult.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
K.G. Noeske P. Papaderos L.M. Cairós K.J. Fricke 《Astrophysics and Space Science》2003,284(2):615-618
We present deep Near-Infrared (NIR) imaging of Blue Compact Dwarf Galaxies (BCDs), allowing for the first time to derive and
systematize the NIR structural properties of their stellar low-surface brightness (LSB) host galaxies. Compared to optical
data, NIR images, being less contamined by the extended stellar and ionized gas emission from the starburst, permit to study
the LSB host galaxy closer to its center. We find that radial surface brightness profiles (SBPs) of the LSB hosts show at
large radii a mostly exponential intensity distribution, in agreement with previous optical studies. At small to intermediate
radii, however, the NIR data reveal an inwards flattening with respect to the outer exponential slope (`type V SBPs', Binggeli
and Cameron, 1991) in the LSB component of more than one half of the sample BCDs. This result may constitute an important
observational constraint to the dynamics and evolution of BCDs. We apply a modified exponential fitting function (Papaderos
et al., 1996a) to parametrize and systematically study type V profiles in BCDs. A Sérsic law is found to be less suitable
for studying the LSB component of BCDs, since it yields very uncertain solutions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Landscape evolution models provide a way to determine erosion rates and landscape stability over times scales from tens to thousands of years. The SIBERIA and CAESAR landscape evolution models both have the capability to simulate catchment–wide erosion and deposition over these time scales. They are both cellular, operate over a digital elevation model of the landscape, and represent fluvial and slope processes. However, they were initially developed to solve research questions at different time and space scales and subsequently the perspective, detail and process representation vary considerably between the models. Notably, CAESAR simulates individual events with a greater emphasis on fluvial processes whereas SIBERIA averages erosion rates across annual time scales. This paper describes how both models are applied to Tin Camp Creek, Northern Territory, Australia, where soil erosion rates have been closely monitored over the last 10 years. Results simulating 10 000 years of erosion are similar, yet also pick up subtle differences that indicate the relative strengths and weaknesses of the two models. The results from both the SIBERIA and CAESAR models compare well with independent field data determined for the site over different time scales. Representative hillslope cross‐sections are very similar between the models. Geomorphologically there was little difference between the modelled catchments after 1000 years but significant differences were revealed at longer simulation times. Importantly, both models show that they are sensitive to input parameters and that hydrology and erosion parameter derivation has long‐term implications for sediment transport prediction. Therefore selection of input parameters is critical. This study also provides a good example of how different models may be better suited to different applications or research questions. Copyright © 2010 John Wiley & Sons, Ltd and Commonwealth of Australia 相似文献
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