Defining And Measuring Green FDI: An Exploratory Review Of Existing Work And Evidence

This paper was developed at the request of the OECD Working Party of the Investment Committee to document efforts to date to define and measure green FDI and to investigate the practicability of various possible definitions, as well as to identify investment policy restrictions to green FDI. It does so by reviewing the literature and existing work on the contributions of FDI to the environment; by providing a two-part definition of green FDI; and by discussing various assumptions necessary to estimate the magnitude of \u27green\u27 FDI

Infalling Faint [OII] Emitters in Abell 851. I. Spectroscopic Confirmation of Narrowband-Selected Objects

We report on a spectroscopic confirmation of narrowband-selected [OII] emitters in Abell 851 catalogued by Martin et al. (2000). The optical spectra obtained from the Keck I Low Resolution Imaging Spectrometer (LRIS) and Keck II Deep Imaging Multi-Object Spectrograph (DEIMOS) have confirmed [OII]3727 emission in narrowband-selected cluster [OII] candidates at a 85% success rate for faint (i <~ 25) blue (g-i < 1) galaxies. The rate for the successful detection of [OII] emission is a strong function of galaxy color, generally proving the efficacy of narrowband [OII] search supplemented with broadband colors in selecting faint cluster galaxies with recent star formation. Balmer decrement-derived reddening measurements show a high degree of reddening [E(B-V) >~ 0.5] in a significant fraction of this population. Even after correcting for dust extinction, the [OII]/Ha line flux ratio for the high-E(B-V) galaxies remains generally lower by a factor of ~2 than the mean [OII]/Ha ratios reported by the studies of nearby galaxies. The strength of [OII] equivalent width shows a negative trend with galaxy luminosity while the Ha equivalent width does not appear to depend as strongly on luminosity. This in part is due to the high amount of reddening observed in luminous galaxies. Furthermore, emission line ratio diagnostics show that AGN-like galaxies are abundant in the high luminosity end of the cluster [OII]-emitting sample, with only moderately strong [OII] equivalent widths, consistent with a scenario of galaxy evolution connecting AGNs and suppression of star-forming activity in massive galaxies.Comment: 11 pages (LaTeX emulateapj), 8 figures, to appear in ApJ. A version with high resolution figures available from the lead autho

The Color-Magnitude Relation in Coma: Clues to the Age and Metallicity of Cluster Populations

We have observed three fields of the Coma cluster of galaxies with a narrow band (modified Stromgren) filter system. Observed galaxies include 31 in the vicinity of NGC 4889, 48 near NGC 4874, and 60 near NGC 4839 complete to M_5500=-18 in all three subclusters. Spectrophotometric classification finds all three subclusters of Coma to be dominated by red, E type (ellipticals/S0's) galaxies with a mean blue fraction, f_B, of 0.10. The blue fraction increases to fainter luminosities, possible remnants of dwarf starburst population or the effects of dynamical friction removing bright, blue galaxies from the cluster population by mergers. We find the color-magnitude (CM) relation to be well defined and linear over the range of M_5500=-13 to -22. After calibration to multi-metallicity models, bright ellipticals are found to have luminosity weighted mean [Fe/H] values between -0.5 and +0.5, whereas low luminosity ellipticals have [Fe/H] values ranging from -2 to solar. The lack of CM relation in our continuum color suggests that a systematic age effect cancels the metallicity effects in this bandpass. This is confirmed with our age index which finds a weak correlation between luminosity and mean stellar age in ellipticals such that the stellar populations of bright ellipticals are 2 to 3 Gyrs younger than low luminosity ellipticals.Comment: 26 pages AAS LaTeX, 6 figures, accepted for publication in A

A possible observational bias in the estimation of the virial parameter in virialized clumps

The dynamics of massive clumps, the environment where massive stars originate, is still unclear. Many theories predict that these regions are in a state of near-virial equilibrium, or near energy equi-partition, while others predict that clumps are in a sub-virial state. Observationally, the majority of the massive clumps are in a sub-virial state with a clear anti-correlation between the virial parameter $\alpha_{vir}$ and the mass of the clumps $M_{c}$, which suggests that the more massive objects are also the more gravitationally bound. Although this trend is observed at all scales, from massive clouds down to star-forming cores, theories do not predict it. In this work we show how, starting from virialized clumps, an observational bias is introduced in the specific case where the kinetic and the gravitational energies are estimated in different volumes within clumps and how it can contribute to the spurious $\alpha_{vir}-M_{c}$ anti-correlation in these data. As a result, the observed effective virial parameter $\tilde{\alpha}_{eff}<\alpha_{vir}$, and in some circumstances it might not be representative of the virial state of the observed clumps.Comment: A&A letter, accepte

ALFALFA HI Data Stacking III. Comparison of environmental trends in HI gas mass fraction and specific star formation rate

It is well known that both the star formation rate and the cold gas content of a galaxy depend on the local density out to distances of a few Megaparsecs. In this paper, we compare the environmental density dependence of the atomic gas mass fractions of nearby galaxies with the density dependence of their central and global specific star formation rates. We stack HI line spectra extracted from the Arecibo Legacy Fast ALFA survey centered on galaxies with UV imaging from GALEX and optical imaging/spectroscopy from SDSS. We use these stacked spectra to evaluate the mean atomic gas mass fraction of galaxies in bins of stellar mass and local density. For galaxies with stellar masses less than 10^10.5 M_sun, the decline in mean atomic gas mass fraction with density is stronger than the decline in mean global and central specific star formation rate. The same conclusion does not hold for more massive galaxies. We interpret our results as evidence for ram-pressure stripping of atomic gas from the outer disks of low mass satellite galaxies. We compare our results with the semi-analytic recipes of Guo et al. (2011) implemented on the Millennium II simulation. These models assume that only the diffuse gas surrounding satellite galaxies is stripped, a process that is often termed "strangulation". We show that these models predict relative trends in atomic gas and star formation that are in disagreement with observations. We use mock catalogues generated from the simulation to predict the halo masses of the HI-deficient galaxies in our sample. We conclude that ram-pressure stripping is likely to become effective in dark matter halos with masses greater than 10^13 M_sun.Comment: 12 pages, 10 figures. Accepted for publication in MNRA

Luminosity Density of Galaxies and Cosmic Star Formation Rate from Lambda-CDM Hydrodynamical Simulations

We compute the cosmic star formation rate (SFR) and the rest-frame comoving luminosity density in various pass-bands as a function of redshift using large-scale \Lambda-CDM hydrodynamical simulations with the aim of understanding their behavior as a function of redshift. To calculate the luminosity density of galaxies, we use an updated isochrone synthesis model which takes metallicity variations into account. The computed SFR and the UV-luminosity density have a steep rise from z=0 to 1, a moderate plateau between z=1 - 3, and a gradual decrease beyond z=3. The raw calculated results are significantly above the observed luminosity density, which can be explained either by dust extinction or the possibly inappropriate input parameters of the simulation. We model the dust extinction by introducing a parameter f; the fraction of the total stellar luminosity (not galaxy population) that is heavily obscured and thus only appears in the far-infrared to sub-millimeter wavelength range. When we correct our input parameters, and apply dust extinction with f=0.65, the resulting luminosity density fits various observations reasonably well, including the present stellar mass density, the local B-band galaxy luminosity density, and the FIR-to-submm extragalactic background. Our result is consistent with the picture that \sim 2/3 of the total stellar emission is heavily obscured by dust and observed only in the FIR. The rest of the emission is only moderately obscured which can be observed in the optical to near-IR wavelength range. We also argue that the steep falloff of the SFR from z=1 to 0 is partly due to the shock-heating of the universe at late times, which produces gas which is too hot to easily condense into star-forming regions.Comment: 25 pages, 6 figures. Accepted version in ApJ. Substantially revised from the previous version. More emphasis on the comparison with various observations and the hidden star formation by dust extinctio

The triggering probability of radio-loud AGN: A comparison of high and low excitation radio galaxies in hosts of different colors

Low luminosity radio-loud active galactic nuclei (AGN) are generally found in massive red elliptical galaxies, where they are thought to be powered through gas accretion from their surrounding hot halos in a radiatively inefficient manner. These AGN are often referred to as "low-excitation" radio galaxies (LERGs). When radio-loud AGN are found in galaxies with a young stellar population and active star formation, they are usually high-power radiatively-efficient radio AGN ("high-excitation", HERG). Using a sample of low-redshift radio galaxies identified within the Sloan Digital Sky Survey (SDSS), we determine the fraction of galaxies that host a radio-loud AGN, $f_{RL}$, as a function of host galaxy stellar mass, $M_*$, star formation rate, color (defined by the 4000 \angstrom break strength), radio luminosity and excitation state (HERG/LERG). We find the following: 1. LERGs are predominantly found in red galaxies. 2. The radio-loud AGN fraction of LERGs hosted by galaxies of any color follows a $f^{LE}_{RL} \propto M^{2.5}_*$ power law. 3. The fraction of red galaxies hosting a LERG decreases strongly for increasing radio luminosity. For massive blue galaxies this is not the case. 4. The fraction of green galaxies hosting a LERG is lower than that of either red or blue galaxies, at all radio luminosities. 5. The radio-loud AGN fraction of HERGs hosted by galaxies of any color follows a $f^{HE}_{RL} \propto M^{1.5}_*$ power law. 6. HERGs have a strong preference to be hosted by green or blue galaxies. 7. The fraction of galaxies hosting a HERG shows only a weak dependence on radio luminosity cut. 8. For both HERGs and LERGs, the hosting probability of blue galaxies shows a strong dependence on star formation rate. This is not observed in galaxies of a different color.[abridged]Comment: 7 pages, 6 figure

Cosmological Origin of the Stellar Velocity Dispersions in Massive Early-Type Galaxies

We show that the observed upper bound on the line-of-sight velocity dispersion of the stars in an early-type galaxy, sigma<400km/s, may have a simple dynamical origin within the LCDM cosmological model, under two main hypotheses. The first is that most of the stars now in the luminous parts of a giant elliptical formed at redshift z>6. Subsequently, the stars behaved dynamically just as an additional component of the dark matter. The second hypothesis is that the mass distribution characteristic of a newly formed dark matter halo forgets such details of the initial conditions as the stellar "collisionless matter" that was added to the dense parts of earlier generations of halos. We also assume that the stellar velocity dispersion does not evolve much at z<6, because a massive host halo grows mainly by the addition of material at large radii well away from the stellar core of the galaxy. These assumptions lead to a predicted number density of ellipticals as a function of stellar velocity dispersion that is in promising agreement with the Sloan Digital Sky Survey data.Comment: ApJ, in press (2003); matches published versio

Time Evolution of Galaxy Formation and Bias in Cosmological Simulations

The clustering of galaxies relative to the mass distribution declines with time because: first, nonlinear peaks become less rare events; second, the densest regions stop forming new galaxies because gas there becomes too hot to cool and collapse; third, after galaxies form, they are gravitationally ``debiased'' because their velocity field is the same as the dark matter. To show these effects, we perform a hydrodynamic cosmological simulation and examine the density field of recently formed galaxies as a function of redshift. We find the bias b_* of recently formed galaxies (the ratio of the rms fluctuations of these galaxies and mass), evolves from 4.5 at z=3 to around 1 at z=0, on 8 h^{-1} Mpc comoving scales. The correlation coefficient r_* between recently formed galaxies and mass evolves from 0.9 at z=3 to 0.25 at z=0. As gas in the universe heats up and prevents star formation, star-forming galaxies become poorer tracers of the mass density field. After galaxies form, the linear continuity equation is a good approximation to the gravitational debiasing, even on nonlinear scales. The most interesting observational consequence of the simulations is that the linear regression of the star-formation density field on the galaxy density field evolves from about 0.9 at z=1 to 0.35 at z=0. These effects also provide a possible explanation for the Butcher-Oemler effect, the excess of blue galaxies in clusters at redshift z ~ 0.5. Finally, we examine cluster mass-to-light ratio estimates of Omega, finding that while Omega(z) increases with z, one's estimate Omega_est(z) decreases. (Abridged)Comment: 31 pages of text and figures; submitted to Ap