The Upper Ocean at the End of an Ice Age: Using Proxies in Benthic Foraminifera to Investigate Intermediate Water Changes During the Last Glacial Termination

The ocean is an important component of the global climate system and plays a key role as a storage reservoir for heat and carbon. Under glacial conditions, the ocean sequestered carbon from the atmosphere, contributing to a cooler global climate. During the last glacial termination, that carbon was released back into the atmosphere, but the exact timing and mechanisms of this transfer are still not fully understood. This study examines waters from the intermediate depths of the Southern Ocean to gain insight into deglacial processes. Intermediate waters are capable of reacting to climate change on decadal timescales, making them a good candidate for catching the early part of deglacial changes. Geochemical proxies in benthic foraminifera provide information on the physical and chemical conditions of these water masses. Prior to applying the Mg/Ca–temperature proxy downcore, we performed a coretop calibration using the species Uvigerina peregrina for our southwest Pacific site. Thorough examination of coretop conditions and foraminifer chemistry yieled a globally-applicable Mg/Ca–temperature calibration, and a series of recommendations for utilizing U. peregrina in paleotemperature reconstructions. Using the resulting calibration as well as a calibration for a second species, Hoeglundina elegans, we reconstructed a paleotemperature record for site 79JPC (1163 m water depth), located in New Zealand’s Bay of Plenty. Temperatures of Antarctic Intermediate Water (AAIW) at this site support the hypothesis of a rapid global warming early during the last glacial termination, and provide further evidence for deglacial changes occurring on timescales much more rapid than those of the continental ice sheets. For a second perspective on deglacial changes in AAIW, we applied a similar approach to site 50GGC, located in the Indian Sector of the Southern Ocean. Using Cibicidoides wuellerstorfi and Cibicidoides kullenbergi, we reconstructed paleotemperature as well as carbonate ion concentrations. Unlike AAIW records from the Pacific and Atlantic basins, those at 50GGC show greater stability and a lower magnitude of change. The uniqueness of the records from 50GGC highlights the need for further study in this basin, and the need to separate concepts of “Indo-Pacific” deglacial change into “Indian sector” and “Pacific sector” components

Assessing the Reliability of the Benthic Mg/Ca–Temperature Proxy: a Uvigerina Core-top Study from New Zealand

Sediment cores from New Zealand’s Bay of Plenty and the Chatham Rise in the Southwest Pacific were sampled to establish a regional Mg/Ca–temperature calibration for the benthic foraminifer Uvigerina peregrina. Comparison of foraminiferal Mg/Ca from core-top sediments to local bottom water temperatures reveals a Mg/Ca–temperature relationship broadly consistent with previously published calibrations. In addition to bottom water temperatures, other environmental parameters are examined for possible influence on the Mg/Ca of foraminiferal calcite. Elderfield et al. (2006) proposed that such parameters may exert an influence at colder temperatures, particularly below temperatures of ~3oC (e.g. Lear et al., 2002; Elderfield et al., 2006; Bryan and Marchitto, 2008). Multiple cores, from water depths between 2400 and 3300 meters, yielded unexpectedly high Mg/Ca ratios (~1.35 mmol/mol) given the ambient bottom water temperatures of ~2oC. Several non-temperature influences were ruled out as the possible cause of the high Mg/Ca measurements. These include morphotype variations, dissolution, down-slope transport, inorganic calcite overgrowths, and carbonate ion saturation. Further analyses, including SEM/EDS analysis of the interior of test chambers, revealed the presence of aluminosilicate crystals growing within chambers of U. peregrina. It is hypothesized that authigenic aluminosilicate growths may present difficulties in measuring and interpreting Mg/Ca in infaunal foraminifera by contributing additional cations during analysis. This affects sediments from New Zealand, and may also occur in other locations. The chemical conditions required for such aluminosilicate precipitation are expected to include high detrital sediment inputs (i.e. fluvial or volcanic), intense surface ocean productivity (i.e. high biogenic silica flux), and high dissolved inorganic carbon concentrations in the water mass overlying the seafloor. Due to the widespread use of the benthic Mg/Ca paleotemperature proxy, it is important to identify any factors that could potentially complicate its use or interpretation. The observed aluminosilicate grains emphasize the need to look beyond the carbonate system when considering diagenetic influences on foraminiferal calcite. Factors such as pore water chemistry and sediment type could exert a significant influence on Mg/Ca measurements, potentially overwriting the Mg/Ca–temperature signal of foraminiferal calcite. Identifying the presence of silicate contaminants and the conditions that cause them to precipitate could enable a better understanding of the factors leading to Mg/Ca measurements that reflect factors other than primary temperature control. Our results suggest that SEM imaging of foraminifer chamber interiors, particularly in areas susceptible to aluminosilicate precipitation, should be done as part of the sample selection process, both in core-top sediments and in paleo records, to ensure production of quality Mg/Ca datasets without diagenetic overprinting

Thermal unfolding of holo and apo pseudoazurin

The role of the copper ion in the thermal unfolding of pseudoazurin has been investigated by differential scanning calorimetry, optical density and fluorescence. In the presence of copper the denaturation of pseudoazurin (holo form) is irreversible and scan rate dependent. The melting temperature ranges between 60.0 and 67.3◦C, depending on the scan rate and the technique used. The DSC data analysis indicates that the denaturation pathway of the holo pseudoazurin is described by the classical Lumry-Eyring model, N ⇔ U ⇒ F. The simulation of the experimental DSC profiles according to this model has allowed the calculation of the thermodynamic and kinetic parameters related to the two steps. The destabilization of the copper active site and of the hydrophobic core precedes the global denaturation of the protein. The removal of the copper ion (apo from) significantly reduces the stability of the protein: the denaturation occurs at 41.8◦C. Moreover, the thermal unfolding of apo pseudoazurin is compatible with a two-state reversible process, N ⇔ U

Intrinsic Absorption in the Spectrum of Mrk 279: Simultaneous Chandra, FUSE, and STIS Observations

We present a study of the intrinsic X-ray and far-ultraviolet absorption in the Seyfert 1.5 galaxy Markarian 279 using simultaneous observations from the Chandra X-ray Observatory, the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope, and the Far Ultraviolet Spectroscopic Explorer (FUSE). We also present FUSE observations made at three additional epochs. We detect the Fe K-alpha emission line in the Chandra spectrum, and its flux is consistent with the low X-ray continuum flux level of Mrk 279 at the time of the observation. Due to low signal-to-noise ratios in the Chandra spectrum, no O VII or O VIII absorption features are observable in the Chandra data, but the UV spectra reveal strong and complex absorption from HI and high-ionization species such as O VI, N V, and C IV, as well as from low-ionization species such as C III, N III, C II, and N II in some velocity components. The far-UV spectral coverage of the FUSE data provides information on high-order Lyman series absorption, which we use to calculate the optical depths and line and continuum covering fractions in the intrinsic HI absorbing gas in a self-consistent fashion. The UV continuum flux of Mrk 279 decreases by a factor of ~7.5 over the time spanning these observations and we discuss the implications of the response of the absorption features to this change. From arguments based on the velocities, profile shapes, covering fractions and variability of the UV absorption, we conclude that some of the absorption components, particularly those showing prominent low-ionization lines, are likely associated with the host galaxy of Mrk 279, and possibly with its interaction with a close companion galaxy, while the remainder arises in a nuclear outflow.Comment: To appear in 2004 May ApJS; double-column format; 58 pages, incl. 29 figures, 9 tables; minor changes to tex

A New H I Survey of Active Galaxies

We have conducted a new Arecibo survey for H I emission for 113 galaxies with broad-line (type 1) active galactic nuclei (AGNs) out to recession velocities as high as 35,000 km/s. The primary aim of the study is to obtain sensitive H I spectra for a well-defined, uniformly selected sample of active galaxies that have estimates of their black hole masses in order to investigate correlations between H I properties and the characteristics of the AGNs. H I emission was detected in 66 out of the 101 (65%) objects with spectra uncorrupted by radio frequency interference, among which 45 (68%) have line profiles with adequate signal-to-noise ratio and sufficiently reliable inclination corrections to yield robust deprojected rotational velocities. This paper presents the basic survey products, including an atlas of H I spectra, measurements of H I flux, line width, profile asymmetry, optical images, optical spectroscopic parameters, as well as a summary of a number of derived properties pertaining to the host galaxies. To enlarge our primary sample, we also assemble all previously published H I measurements of type 1 AGNs for which can can estimate black hole masses, which total an additional 53 objects. The final comprehensive compilation of 154 broad-line active galaxies, by far the largest sample ever studied, forms the basis of our companion paper, which uses the H I database to explore a number of properties of the AGN host galaxies.Comment: To appear in ApJS; 31 pages. Preprint will full-resolution figures can be downloaded from http://www.ociw.edu/~lho/preprints/ms1.pd

VLT/ISAAC Spectra of the H-beta Region in Intermediate Redshift Quasars

We present high S/N spectra of the H-beta region in 17 intermediate redshift (0.85 le z le 2.5) quasars. The spectra represent first results of our campaign to test the redshift/luminosity robustness of the so-called Eigenvector 1 (E1) parameter space as developed for low redshift AGN in Sulentic et al. (2000). The new quasars span the luminosity range -26 ge M_B ge -29 while most of our low redshift sample (n=215) involve sources in the range -19 ge M_B ge -26. The high redshift sources show E1 parameter values and domain occupation that are similar to our low redshift sample supporting earlier findings that E1 parameters are uncorrelated with source luminosity. Elementary accretion theory can account for a systematic increase of the minimum observed H-beta profile width with source luminosity. Narrow line Seyfert 1 sources with M_B = -28 show FWHM(H-beta) as much as 2000 km/s broader than those with M_B = -22. A possible change in the higher redshift/luminosity sources involves systematically weaker [OIII]4959,5007 narrow line emission.Comment: 17 pages, 13 figures, accepted by A&A; added references and minor correction

Hβ spectra of high-redshift QSOs: Eigenvector 1 at high luminosities

n/

The ESO Slice Project (ESP) galaxy redshift survey: III. The Sample

The ESO Slice Project (ESP) is a galaxy redshift survey extending over about 23 square degrees, in a region near the South Galactic Pole. The survey is ~85% complete to the limiting magnitude b_J=19.4 and consists of 3342 galaxies with redshift determination. The ESP survey is intermediate between shallow, wide angle samples and very deep, one-dimensional pencil beams; the spanned volume is ~ 5 x 10^4 Mpc^3 at the sensitivity peak (z ~ 0.1). In this paper we present the description of the observations and of the data reduction, the ESP redshift catalogue and the analysis of the quality of the velocity determinations.Comment: 10 pages, 4 encapsulated figures, uses A&A LATEX; A&A Supplements in press (June 1998 issue

The Host Galaxies of Narrow-Line Seyfert 1s: Evidence for Bar-Driven Fueling

We present a study of the host-galaxy morphologies of narrow- and broad-line Seyfert 1 galaxies (NLS1s and BLS1s) based on broad-band optical images from the Hubble Space Telescope archives. We find that large-scale stellar bars, starting at ~1 kpc from the nucleus, are much more common in NLS1s than BLS1s. Furthermore, the fraction of NLS1 spirals that have bars increases with decreasing full-width at half-maximum (FWHM) of the broad component of H-beta. These results suggest a link between the large-scale bars, which can support high fueling rates to the inner kpc, and the high mass-accretion rates associated with the supermassive black holes in NLS1s.Comment: 19 pages, 4 figures (1a, 1b, 2, and 3), Accepted for publication in the Astronomical Journa