Dr Fraser Clarke

Abstract:

We present a stellar mass-metallicity relation at z ~ 1.4 with an unprecedentedly large sample of ~340 star-forming galaxies obtained with FibreMulti-Object Spectrograph (FMOS) on the Subaru Telescope. We observed K-band selected galaxies at 1.2 ≤ zph ≤ 1.6 in the Subaru XMM-Newton Deep Survey/Ultra Deep Survey fields with M*> 109.5M⊙, and expected F(Hα) > 5 × 10-17 erg s-1 cm-2. Among the observed ~1200 targets, 343 objects show significant Ha emission lines. The gas-phase metallicity is obtained from [N II] λ6584/Hα line ratio, after excluding possible active galactic nuclei. Due to the faintness of the [N II] λ6584 lines, we apply the stacking analysis and derive the mass-metallicity relation at z ~ 1.4. Our results are compared to past results at different redshifts in the literature. The mass-metallicity relation at z ~ 1.4 is located between those at z ~ 0.8 and z ~ 2.2; it is found that the metallicity increases with decreasing redshift from z ~ 3 to z ~ 0 at fixed stellar mass. Thanks to the large size of the sample, we can study the dependence of the mass-metallicity relation on various galaxy physical properties. The average metallicity from the stacked spectra is close to the local Fundamental Metallicity Relation (FMR) in the higher metallicity part but >0.1 dex higher in metallicity than the FMR in the lower metallicity part.We find that galaxies with larger E(B -V), B -R and R -H colours tend to show higher metallicity by ~0.05 dex at fixed stellar mass. We also find relatively clearer size dependence that objects with smaller half-light radius tend to show higher metallicity by ~0.1 dex at fixed stellar mass, especially in the low-mass part. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Abstract:

We report results of a direct imaging survey for giant planets around 80 members of the Beta Pic, TW Hya, Tucana-Horologium, AB Dor, and Hercules-Lyra moving groups, observed as part of the Gemini NICI Planet-Finding Campaign. For this sample, we obtained median contrasts of ΔH=13.9 mag at 1" in combined CH4 narrowband ADI+SDI mode and median contrasts of ΔH=15.1 mag at 2" in H-band ADI mode. We found numerous (>70) candidate companions in our survey images. Some of these candidates were rejected as common-proper motion companions using archival data; we reobserved with NICI all other candidates that lay within 400 AU of the star and were not in dense stellar fields. The vast majority of candidate companions were confirmed as background objects from archival observations and/or dedicated NICI campaign followup. Four co-moving companions of brown dwarf or stellar mass were discovered in this moving group sample: PZ Tel B (36+-6 MJup, 16.4+-1.0 AU, Biller et al. 2010), CD -35 2722B (31+-8 MJup, 67+-4 AU, Wahhaj et al. 2011), HD 12894B (0.46+-0.08 MSun, 15.7+-1.0 AU), and BD+07 1919C (0.20+-0.03 MSun, 12.5+-1.4 AU). From a Bayesian analysis of the achieved H band ADI and ASDI contrasts, using power-law models of planet distributions and hot-start evolutionary models, we restrict the frequency of 1--20 MJup companions at semi-major axes from 10--150 AU to <18% at a 95.4% confidence level using DUSTY models and to <6% at a 95.4% using COND models.