Fabrication of a repulsive-type magnetic bearing using a novel arrangement of permanent magnets for vertical-rotor suspension

A repulsive-type magnetic bearing system has been fabricated in which the rotor of a vertical-shaft-type motor is levitated due to the repulsive force between two sets of permanent magnets. A novel arrangement of permanent magnets has been reported here, which has made the suspension of the rotor possible. The system is planned to be applied for pumping milks and other related products in the New Zealand dairy industry

MgII absorption systems with W_0 > 0.1 \AA for a radio selected sample of 77 QSOs and their associated magnetic fields at high redshifts

We present a catalogue of MgII absorption systems obtained from high resolution UVES/VLT data of 77 QSOs in the redshift range 0.6 < z < 2.0, and down to an equivalent width W_0 > 0.1 \AA. The statistical properties of our sample are found to be in agreement with those from previous work in the literature. However, we point out that the previously observed increase with redshift of dN/dz for weak absorbers, pertains exclusively to very weak absorbers with W_0 < 0.1 \AA. Instead, dN/dz for absorbers with W_0 in the range 0.1-0.3 \AA actually decreases with redshift, similarly to the case of strong absorbers. We then use this catalogue to extend our earlier analysis of the links between the Faraday Rotation Measure of the quasars and the presence of intervening MgII absorbing systems in their spectra. In contrast to the case with strong MgII absorption systems W_0 > 0.3 \AA, the weaker systems do not contribute significantly to the observed Rotation Measure of the background quasars. This is possibly due to the higher impact parameters of the weak systems compared to strong ones, suggesting that the high column density magnetized material that is responsible for the Faraday Rotation is located within about 50 kpc of the galaxies. Finally, we show that this result also rules out the possibility that some unexpected secondary correlation between the quasar redshift and its intrinsic Rotation Measure is responsible for the association of high Rotation Measure and strong intervening MgII absorption that we have presented elsewhere, since this would have produced an equal effect for the weak absorption line systems, which exhibit a very similar distribution of quasar redshifts.Comment: Accepted for publication in ApJ. 12 pages, 8 figure

Orbiting Circum-galactic Gas as a Signature of Cosmological Accretion

We use cosmological SPH simulations to study the kinematic signatures of cool gas accretion onto a pair of well-resolved galaxy halos. Cold-flow streams and gas-rich mergers produce a circum-galactic component of cool gas that generally orbits with high angular momentum about the galaxy halo before falling in to build the disk. This signature of cosmological accretion should be observable using background-object absorption line studies as features that are offset from the galaxy's systemic velocity by ~100 km/s. Accreted gas typically co-rotates with the central disk in the form of a warped, extended cold flow disk, such that the observed velocity offset is in the same direction as galaxy rotation, appearing in sight lines that avoid the galactic poles. This prediction provides a means to observationally distinguish accreted gas from outflow gas: the accreted gas will show large one-sided velocity offsets in absorption line studies while radial/bi-conical outflows will not (except possibly in special polar projections). This rotation signature has already been seen in studies of intermediate redshift galaxy-absorber pairs; we suggest that these observations may be among the first to provide indirect observational evidence for cold accretion onto galactic halos. Cold mode halo gas typically has ~3-5 times more specific angular momentum than the dark matter. The associated cold mode disk configurations are likely related to extended HI/XUV disks seen around galaxies in the local universe. The fraction of galaxies with extended cold flow disks and associated offset absorption-line gas should decrease around bright galaxies at low redshift, as cold mode accretion dies out.Comment: 15 pages, 9 figures, edited to match published version. Includes expanded discussion, with primary results unchange

ZFIRE: The Evolution of the Stellar Mass Tully-Fisher Relation to Redshift 2.0 < Z < 2.5 with MOSFIRE

Using observations made with MOSFIRE on Keck I as part of the ZFIRE survey, we present the stellar mass Tully-Fisher relation at 2.0 < z < 2.5. The sample was drawn from a stellar mass limited, Ks-band selected catalog from ZFOURGE over the CANDELS area in the COSMOS field. We model the shear of the Halpha emission line to derive rotational velocities at 2.2X the scale radius of an exponential disk (V2.2). We correct for the blurring effect of a two-dimensional PSF and the fact that the MOSFIRE PSF is better approximated by a Moffat than a Gaussian, which is more typically assumed for natural seeing. We find for the Tully-Fisher relation at 2.0 < z < 2.5 that logV2.2 =(2.18 +/- 0.051)+(0.193 +/- 0.108)(logM/Msun - 10) and infer an evolution of the zeropoint of Delta M/Msun = -0.25 +/- 0.16 dex or Delta M/Msun = -0.39 +/- 0.21 dex compared to z = 0 when adopting a fixed slope of 0.29 or 1/4.5, respectively. We also derive the alternative kinematic estimator S0.5, with a best-fit relation logS0.5 =(2.06 +/- 0.032)+(0.211 +/- 0.086)(logM/Msun - 10), and infer an evolution of Delta M/Msun= -0.45 +/- 0.13 dex compared to z < 1.2 if we adopt a fixed slope. We investigate and review various systematics, ranging from PSF effects, projection effects, systematics related to stellar mass derivation, selection biases and slope. We find that discrepancies between the various literature values are reduced when taking these into account. Our observations correspond well with the gradual evolution predicted by semi-analytic models.Comment: 21 pages, 14 figures, 1 appendix. Accepted for publication by Apj, February 28, 201

The Relation Between Galaxy ISM and Circumgalactic OVI Gas Kinematics Derived from Observations and Λ\LambdaCDM Simulations

We present the first galaxy-OVI absorption kinematic study for 20 absorption systems (EW>0.1~{\AA}) associated with isolated galaxies (0.15$<z<$0.55) that have accurate redshifts and rotation curves obtained using Keck/ESI. Our sample is split into two azimuthal angle bins: major axis ($\Phi<25^{\circ}$) and minor axis ($\Phi>33^{\circ}$). OVI absorption along the galaxy major axis is not correlated with galaxy rotation kinematics, with only 1/10 systems that could be explained with rotation/accretion models. This is in contrast to co-rotation commonly observed for MgII absorption. OVI along the minor axis could be modeled by accelerating outflows but only for small opening angles, while the majority of the OVI is decelerating. Along both axes, stacked OVI profiles reside at the galaxy systemic velocity with the absorption kinematics spanning the entire dynamical range of their galaxies. The OVI found in AMR cosmological simulations exists within filaments and in halos of ~50 kpc surrounding galaxies. Simulations show that major axis OVI gas inflows along filaments and decelerates as it approaches the galaxy while increasing in its level of co-rotation. Minor axis outflows in the simulations are effective within 50-75 kpc beyond that they decelerate and fall back onto the galaxy. Although the simulations show clear OVI kinematic signatures they are not directly comparable to observations. When we compare kinematic signatures integrated through the entire simulated galaxy halo we find that these signatures are washed out due to full velocity distribution of OVI throughout the halo. We conclude that OVI alone does not serve as a useful kinematic indicator of gas accretion, outflows or star-formation and likely best probes the halo virial temperature.Comment: 24 pages, 21 figures, 4 tables. Accepted to ApJ on November 14, 201

Gas Accretion in Star-Forming Galaxies

Cold-mode gas accretion onto galaxies is a direct prediction of LCDM simulations and provides galaxies with fuel that allows them to continue to form stars over the lifetime of the Universe. Given its dramatic influence on a galaxy's gas reservoir, gas accretion has to be largely responsible for how galaxies form and evolve. Therefore, given the importance of gas accretion, it is necessary to observe and quantify how these gas flows affect galaxy evolution. However, observational data have yet to conclusively show that gas accretion ubiquitously occurs at any epoch. Directly detecting gas accretion is a challenging endeavor and we now have obtained a significant amount of observational evidence to support it. This chapter reviews the current observational evidence of gas accretion onto star-forming galaxies.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics and Space Science Library, eds. A. J. Fox & R. Dav\'e, to be published by Springer. This chapter includes 22 pages with 7 Figure

ZFOURGE: Using Composite Spectral Energy Distributions to Characterize Galaxy Populations at 1<z<4

We investigate the properties of galaxies as they shut off star formation over the 4 billion years surrounding peak cosmic star formation. To do this we categorize $\sim7000$ galaxies from $1<z<4$ into $90$ groups based on the shape of their spectral energy distributions (SEDs) and build composite SEDs with $R\sim 50$ resolution. These composite SEDs show a variety of spectral shapes and also show trends in parameters such as color, mass, star formation rate, and emission line equivalent width. Using emission line equivalent widths and strength of the 4000\AA\ break, $D(4000)$, we categorize the composite SEDs into five classes: extreme emission line, star-forming, transitioning, post-starburst, and quiescent galaxies. The transitioning population of galaxies show modest H$\alpha$ emission ($EW_{\rm REST}\sim40$\AA) compared to more typical star-forming composite SEDs at $\log_{10}(M/M_\odot)\sim10.5$ ($EW_{\rm REST}\sim80$\AA). Together with their smaller sizes (3 kpc vs. 4 kpc) and higher S\'ersic indices (2.7 vs. 1.5), this indicates that morphological changes initiate before the cessation of star formation. The transitional group shows a strong increase of over one dex in number density from $z\sim3$ to $z\sim1$, similar to the growth in the quiescent population, while post-starburst galaxies become rarer at $z\lesssim1.5$. We calculate average quenching timescales of 1.6 Gyr at $z\sim1.5$ and 0.9 Gyr at $z\sim2.5$ and conclude that a fast quenching mechanism producing post-starbursts dominated the quenching of galaxies at early times, while a slower process has become more common since $z\sim2$.Comment: Accepted for publication in The Astrophysical Journa