A study of central galaxy rotation with stellar mass and environment

© 2017. The American Astronomical Society. All rights reserved. We present a pilot analysis of the influence of galaxy stellar mass and cluster environment on the probability of slow rotation in 22 central galaxies at mean redshift z = 0.07. This includes new integral-field observations of five central galaxies selected from the Sloan Digital Sky Survey, observed with the SPIRAL integral-field spectrograph on the Anglo-Australian Telescope. The composite sample presented here spans a wide range of stellar masses, 10.9 < log(M∗/M⊙)lt; 12.0, and are embedded in halos ranging from groups to clusters, 12.9 < log(M 200 Ṁ) < 15.6. We find a mean probability of slow rotation in our sample of P(SR) = 54 ± 7%. Our results show an increasing probability of slow rotation in central galaxies with increasing stellar mass. However, when we examine the dependence of slow rotation on host cluster halo mass, we do not see a significant relationship. We also explore the influence of cluster dominance on slow rotation in central galaxies. Clusters with low dominance are associated with dynamically younger systems. We find that cluster dominance has no significant effect on the probability of slow rotation in central galaxies. These results conflict with a paradigm in which halo mass alone predetermines central galaxy properties

Changes in Kelp and Other Seaweeds Following Elwha Dam Removal

Kelps are ecologically important seaweeds that dominated the nearshore vegetation community prior to dam removal on the Elwha River. Dam removal is expected to trigger a shift from kelps to vegetation types that are characteristic of soft-sediment communities through restoring natural sediment supply. This study is investigating how nearshore vegetation responds to restoration of the natural sediment regime, both initially when large amounts of sediment entrained in the reservoirs are released and over longer time periods. We assessed vegetation at multiple spatial scales using three approaches. First, we measured floating kelp canopy area using aerial photography. Second, we assessed the abundance of understory kelp and seagrasses with towed videography along 50 km of shoreline. Third, scuba divers recorded density of kelp species and other seaweeds along 10 km of shoreline bracketing the river mouth. Results show profound changes in vegetation and a strong gradient in magnitude of impact related to distance from the river mouth. Floating kelp canopy area decreased 74% in the Elwha Drift Cell in the first year following project initiation (year 1), with lower magnitude losses throughout the Strait of Juan de Fuca. Area of prostrate kelps decreased by 45% (400 ha) and of stipitate kelps by 30% (130 ha) in the Elwha Drift Cell in year 1. Mean kelp density near the river mouth decreased 77% in year 1 and 95% in year 2. While all 10 kelp species declined, annuals were more impacted than perennials. In contrast to the general decline, juveniles of several kelp species appeared in late August of year 2, a substantial delay compared to typical spring timing of juvenile growth. What caused the large kelp losses and apparent delay of juvenile growth? Likely candidates include light reduction from the river plume and scour, burial or settlement inhibition from deposition. These candidates will be explored using physical data from the multidisciplinary research effort

Population and dynamical state of the eta Chamaeleontis sparse young open cluster

We report new results in our continuing study of the unique compact (1 pc extent), nearby (d = 97 pc), young (t = 9 Myr) stellar cluster dominated by the B9 star eta Chamaeleontis. An optical photometric survey spanning 1.3 x 1.3 pc adds two M5-M5.5 weak-lined T Tauri (WTT) stars to the cluster inventory which is likely to be significantly complete for primaries with masses > 0.15 M_sun. The cluster now consists of 17 primaries and approximately 9 secondaries lying within 100 AU of their primaries. The apparent distribution of 9:7:1 single:binary:triple systems shows 2-4 x higher multiplicity than in the field main sequence stars, and is comparable to that seen in other pre-main sequence (PMS) populations. The initial mass function (IMF) is consistent with that of rich young clusters and field stars. By extending the cluster IMF to lower masses, we predict 10-14 additional low mass stars with 0.08 < M < 0.15 M-sun and 10-15 brown dwarfs with 0.025 < M < 0.08 M_sun remain to be discovered. The eta Cha cluster extends the established stellar density and richness relationship for young open clusters. The radial distribution of stars is consistent with an isothermal sphere, but mass segregation is present with > 50 percent of the stellar mass residing in the inner 6 arcmin (0.17 pc). Considering that the eta Cha cluster is sparse, diffuse and young, the cluster may be an ideal laboratory for distinguishing between mass segregation that is primordial in nature, or arising from dynamical interaction processes.Comment: 10 pages, 7 figures, 2 tables, accepted for MNRA

Spatial kinematics of Brightest Cluster Galaxies and their close companions from Integral Field Unit spectroscopy

We present Integral Field Unit (IFU) spectroscopy of four brightest cluster galaxies (BCGs) at z~0.1. Three of the BCGs have close companions within a projected radius of 20 kpc and one has no companion within that radius. We calculate the dynamical masses of the BCGs and their companions to be 1.4x10^11<M_dyn (M_solar)<1.5x10^12. We estimate the probability that the companions of the BCGs are bound using the observed masses and velocity offsets. We show that the lowest mass companion (1:4) is not bound while the two nearly equal mass (1:1.45 and 1:1.25) companions are likely to merge with their host BCGs in 0.35 Gyr in major, dry mergers. We conclude that some BCGs continue to grow from major merging even at z~0. We analyse the stellar kinematics of these systems using the \lambda_R parameter developed by the SAURON team. This offers a new and unique means to measure the stellar angular momentum of BCGs and make a direct comparison to other early-type galaxies. The BCGs and their companions have similar ellipticities to those of other early-type galaxies but are more massive. We find that not all these massive galaxies have low \lambda_R_e as one might expect. One of the four BCGs and the two massive companions are found to be fast-rotating galaxies with high angular momentum, thereby providing a new test for models of galaxy evolution and the formation of Intra-Cluster Light.Comment: 5 pages. Accepted for publication in MNRAS Letter

Oceanic loading of wildfire-derived organic compounds from a small mountainous river

Copyright 2008 by the American Geophysical Union.Small mountainous rivers (SMRs) export substantial amounts of sediment into the world's oceans. The concomitant yield of organic carbon (OC) associated with this class of rivers has also been shown to be significant and compositionally unique. We report here excessively high loadings of polycyclic aromatic hydrocarbons (PAHs), lignin, and levoglucosan, discharged from the Santa Clara River into the Santa Barbara Channel. The abundance of PAHs, levoglucosan, and lignin in Santa Barbara Channel sediments ranged from 201.7 to 1232.3 ng gdw−1, 1.3 to 6.9 μg gdw−1, and 0.3 to 2.2 mg per 100 mg of the sedimentary OC, respectively. Assuming a constant rate of sediment accumulation, the annual fluxes of PAHs, levoglucosan, and lignin, to the Santa Barbara Channel were respectively, 885.5 ± 170.2 ng cm−2 a−1, 3.5 ± 1.9 μg cm−2 a−1 and 1.4 ± 0.3 mg per 100 mg OC cm−2 a−1, over ∼30 years. The close agreement between PAHs, levoglucosan, and lignin abundance suggests that the depositional flux of these compounds is largely biomass combustion-derived. To that end, use of the Santa Clara River as a model for SMRs suggests this class of rivers may be one of the largest contributors of pyrolyzed carbon to coastal systems and the open ocean. Wildfire associated carbon discharged from other high yield fluvial systems, when considered collectively, may be a significant source of lignin, pyrolytic PAHs, and other pyrogenic compounds to the ocean. Extrapolating these methods over geologic time may offer useful historical information about carbon sequestration and burial in coastal sediments and affect coastal carbon budgets

Late Little Ice Age palaeoenvironmental records from the Anzali and Amirkola Lagoons (south Caspian Sea): Vegetation and sea level changes

This is a postprint version of the article. The official published article can be found from the link below - Copyright @ 2011 Elsevier Ltd.Two internationally important Ramsar lagoons on the south coast of the Caspian Sea (CS) have been studied by palynology on short sediment cores for palaeoenvironmental and palaeoclimatic investigations. The sites lie within a small area of very high precipitation in a region that is otherwise dry. Vegetation surveys and geomorphological investigations have been used to provide a background to a multidisciplinary interpretation of the two sequences covering the last four centuries. In the small lagoon of Amirkola, the dense alder forested wetland has been briefly disturbed by fire, followed by the expansion of rice paddies from AD1720 to 1800. On the contrary, the terrestrial vegetation reflecting the diversity of the Hyrcanian vegetation around the lagoon of Anzali remained fairly complacent over time. The dinocyst and non-pollen palynomorph assemblages, revealing changes that have occurred in water salinity and water levels, indicate a high stand during the late Little Ice Age (LIA), from AD < 1620 to 1800–1830. In Amirkola, the lagoon spit remained intact over time, whereas in Anzali it broke into barrier islands during the late LIA, which merged into a spit during the subsequent sea level drop. A high population density and infrastructure prevented renewed breaking up of the spit when sea level reached its maximum (AD1995). Similar to other sites in the region around the southern CS, these two lagoonal investigations indicate that the LIA had a higher sea level as a result of more rainfall in the drainage basin of the CS.The coring and the sedimentological analyses were funded by the Iranian National Institute for Oceanography in the framework of a research project entitled “Investigation of the Holocene sediment along the Iranian coast of Caspian Sea: central Guilan”. The radiocarbon date of core HCGL02 was funded by V. Andrieu (Europôle Méditerranéen de l'Arbois, France) and that of core HCGA04 by Brunel University

Nearshore subtidal community response during and after sediment disturbance associated with dam removal

Dam removal is used increasingly to restore aquatic ecosystems and remove unnecessary or high-risk infrastructure. As the number of removals increases, there is a growing understanding about the hydrologic, geomorphic, and ecological responses to these removals. Most dam removal studies, however, focus on river and watershed responses to dam removal. The removal of two dams on the Elwha River provided a unique opportunity to characterize the response of nearshore (coastal) ecosystems. We conducted SCUBA surveys between 2011 and 2022 to quantify trajectories of change in a nearshore ecosystem during and after dam removal. We focused on the degree to which the abundances of kelp, benthic invertebrates, and fish changed in response to patterns of sediment fluxes during and after dam removal. Our findings point to two pathways of response depending on the disturbance mechanism and species type. Sites with persistent sediment deposition were characterized by wholesale community changes that did not recover to a before dam removal condition. Instead, the sites were colonized by new species that were largely absent prior to dam removal. Sites that experienced high turbidity but lacked persistent seafloor deposition were primarily characterized by a reduction in the abundance of kelp and other algae during dam removal and a rapid recovery after sediment flux to the nearshore declined. Dam removal influences on invertebrates and fish at these sites were more variable, benefiting some species and disadvantaging others. In addition to dam removal, sea star wasting syndrome and a marine heatwave exerted distinct controls on subtidal communities during the same period. The loss of the predatory sea star Pycnopodia helianthoides was associated with gains in some of its prey species, and kelp community changes reflected regional trends in ocean temperature and kelp abundance. The results presented here have important implications for understanding the response of marine ecosystems to future dam removals and similar sediment perturbation events

The Evolution of Bat Vestibular Systems in the Face of Potential Antagonistic Selection Pressures for Flight and Echolocation

PMCID: PMC3634842This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Galaxy ecology: groups and low-density environments in the SDSS and 2dFGRS

We analyse the observed correlation between galaxy environment and Hα emission-line strength, using volume-limited samples and group catalogues of 24 968 galaxies at 0.05 < z < 0.095, drawn from the 2dF Galaxy Redshift Survey ( < −19.5) and the Sloan Digital Sky Survey (Mr < −20.6). We characterize the environment by: (1) Σ5, the surface number density of galaxies determined by the projected distance to the fifth nearest neighbour; and (2) ρ1.1 and ρ5.5, three-dimensional density estimates obtained by convolving the galaxy distribution with Gaussian kernels of dispersion 1.1 and 5.5 Mpc, respectively. We find that star-forming and quiescent galaxies form two distinct populations, as characterized by their Hα equivalent width, W0(Hα). The relative numbers of star-forming and quiescent galaxies vary strongly and continuously with local density. However, the distribution of W0(Hα) amongst the star-forming population is independent of environment. The fraction of star-forming galaxies shows strong sensitivity to the density on large scales, ρ5.5, which is likely independent of the trend with local density, ρ1.1. We use two differently selected group catalogues to demonstrate that the correlation with galaxy density is approximately independent of group velocity dispersion, for σ= 200-1000 km s-1. Even in the lowest-density environments, no more than ∼70 per cent of galaxies show significant Hα emission. Based on these results, we conclude that the present-day correlation between star formation rate and environment is a result of short-time-scale mechanisms that take place preferentially at high redshift, such as starbursts induced by galaxy-galaxy interaction