Lickenbrock

Massive galaxies at high-z are known to co-evolve with their circumgalactic medium (CGM). If we want to truly understand the role of the CGM in the early evolution of galaxies and galaxy-clusters, we need to fully explore the multi-phase nature of the CGM. We present two novel science cases that utilize low-surface-brightness observations in the radio regime to better understand the CGM around distant galaxies. At the lowest temperatures, observations of widespread molecular gas are providing evidence for the cold baryon cycle that grows massive galaxies. At the highest temperatures, observations of the Sunyaev-Zeldovich Effect are starting to reveal the effect of quasar feedback onto the hot gas in the CGM. We discuss the critical role that radio interferometers with compact configurations in the millimeter regime will play over the next decade in understanding the crucial role of the multi-phase CGM in galaxy evolution.

Recent advances are presented for multiframe blind deconvolution (MFBD) of ground based telescope imagery for low-earth orbit objects. The iterative algorithm uses the maximum likelihood estimation optimization criterion. It is modeled from a previous well-known algorithm called the expectation-maximization (EM) algorithm. New renditions of the algorithm simplify the phase reconstruction, thereby reducing the complexity of the original EM algorithm. Examples are shown, with and without adaptive optics (AO). The system is being designed for on-the-fly streaming video operation.

Recent advances in multiframe blind deconvolution of ground based telescopes are presented. The paper focuses on practical aspects of the software and algorithm. (1) A computer simulation that models atmospheric turbulence, noise and other aspects, for testing and evaluation of the deconvolution system are explained. (2) A post-processing algorithm that corrects for glint due to specular and other bright reflections is presented. This glint correction is automated by a spatially adaptive scheme that calculates statistics of brightness levels. (3) Efforts to realize computational speed, wherein processing happens on-the-fly at streaming frame rates are underway. The massively parallel processing of graphical processing units (GPUs) and the Compute Unified Device Architecture (CUDA) language are used.

Massive galaxies display extended light profiles that can reach several hundreds of kilo parsecs. These stellar halos provide a fossil record of galaxy assembly histories. Using data that is both wide (~100 square degree) and deep (i>28.5 mag/arcsec^2 in i-band), we present a systematic study of the stellar halos of a sample of more than 3000 galaxies at 0.3 < z < 0.5 with $\log M_{\star}/M_{\odot} > 11.4$. Our study is based on high-quality (0.6 arcsec seeing) imaging data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP), which enables us to individually estimate surface mass density profiles to 100 kpc without stacking. As in previous work, we find that more massive galaxies exhibit more extended outer profiles. When this extended light is not properly accounted for as a result of shallow imaging or inadequate profile modeling, the derived stellar mass function can be significantly underestimated at the highest masses. Across our sample, the ellipticity of outer light profiles increases substantially as we probe larger radii. We show for the first time that these ellipticity gradients steepen dramatically as a function of galaxy mass, but we detect no mass-dependence in outer color gradients. Our results support the two-phase formation scenario for massive galaxies in which outer envelopes are built up at late times from a series of merging events. We provide surface mass surface mass density profiles in a convenient tabulated format to facilitate comparisons with predictions from numerical simulations of galaxy formation.

On 1 October 2015, in the midst of the current Syrian refugee crisis, AJ+, an online news and current events channel produced by the Al Jazeera Media Network, published a video titled “I Was a Boat Person: Vietnamese Refugees Look Back.” The three-and-one-half-minute video features interviews with several Vietnamese Americans who were refugees of the Vietnam War—writers Aimee Phan and Andrew Lam; dean at the City College of San Francisco Minh-Hoa; media consultant Sonny Le; and humanitarian Diep Vuong—and who attest to making escapes just as dangerous as those of Syrian refugees today. The video makes this parallel between the two refugee groups explicit, juxtaposing footage of Vietnamese boat people with that of Syrian boat people in faded black-and-white and sepia tones, so that a viewer cannot immediately distinguish between them. Le says: “God, if you look at homes in Aleppo in Syria, Vietnam looked like that after the war.” This resemblance in visual signifiers is noted when Minh-Hoa says, “When I saw the picture of the little boy on the beach in Turkey, that really brings back lots of sad and horrifying memories.”

3D image reconstruction using light microscope modalities without exogenous contrast agents is proposed and investigated as an approach to produce 3D images of biological samples for live imaging applications. Multimodality and multispectral imaging, used in concert with this 3D optical sectioning approach is also proposed as a way to further produce contrast that could be specific to components in the sample. The methods avoid usage of contrast agents. Contrast agents, such as fluorescent or absorbing dyes, can be toxic to cells or alter cell behavior. Current modes of producing 3D image sets from a light microscope, such as 3D deconvolution algorithms and confocal microscopy generally require contrast agents. Zernike phase contrast (ZPC), transmitted light brightfield (TLB), darkfield microscopy and others can produce contrast without dyes. Some of these modalities have not previously benefitted from 3D image reconstruction algorithms, however. The 3D image reconstruction algorithm is based on an underlying physical model of scattering potential, expressed as the sample’s 3D absorption and phase quantities. The algorithm is based upon optimizing an objective function - the I-divergence - while solving for the 3D absorption and phase quantities. Unlike typical deconvolution algorithms, each microscope modality, such as ZPC or TLB, produces two output image sets instead of one. Contrast in the displayed image and 3D renderings is further enabled by treating the multispectral/multimodal data as a feature set in a mathematical formulation that uses the principal component method of statistics.

We present detailed chemical abundances for $>$20 elements in $\sim$30 globular clusters in M31. These results have been obtained using high resolution ($\lambda/\Delta\lambda\sim$24,000) spectra of their integrated light and analyzed using our original method. The globular clusters have galactocentric radii between 2.5 kpc and 117 kpc, and therefore provide abundance patterns for different phases of galaxy formation recorded in the inner and outer halo of M31. We find that the clusters in our survey have a range in metallicity of $-2.2<$[Fe/H]$<-0.11$. The inner halo clusters cover this full range, while the outer halo globular clusters at R$>$20 kpc have a small range in abundance of [Fe/H]$=-1.6 \pm 0.10$. We also measure abundances of alpha, r- and s-process elements. These results constitute the first abundance pattern constraints for old populations in M31 that are comparable to those known for the Milky Way halo.

ABSTRACTThe presence of abundance inhomogeneities in the CNO elements in globular clusters indicates that these objects sustained extended eras of star formation combined with chemical enrichment. Nonetheless, most globular clusters in the Milky Way are homogeneous in iron-peak elements and the heavier alpha elements. If globular clusters were sites of chemical evolution, then it seems to have occurred at constant iron-peak abundance. This might imply that only nonsupernova stars contributed to the chemical evolution. In this article another scenario is explored, one in which supernovae did participate, but in which the chemical evolution occurred in such a way as to maintain a constant iron-peak abundance, while at the same time establishing CNO and related element inhomogeneities. In order to keep the [Fe/H] abundance homogeneous, a scenario is studied that requires the net protocluster mass (gas plus stars) to be specifically related to the number of supernovae that occur. By comparing models from the literature for element production in metal-poor supernovae and intermediate-mass asymptotic giant branch (IM-AGB) stars, it is found that iron homogeneity plus a pattern of CNO-Na abundance inhomogeneities that reasonably match Milky Way globular clusters can be obtained by combining very low mass supernovae (∼10 M⊙) with relatively high mass IM-AGB stars. Nucleosynthesis within metal-poor stars in the mass range of 7–9 M⊙ could prove useful to understanding the abundances of globular cluster stars.

Abstract The magnetic field pervading our Galaxy is a crucial constituent of the interstellar medium: it mediates the dynamics of interstellar clouds, the energy density of cosmic rays, and the formation of stars (Beck 2005). The field associated with ionized interstellar gas has been determined through observations of pulsars in our Galaxy. Radio-frequency measurements of pulse dispersion and the rotation of the plane of linear polarization, i.e., Faraday rotation, yield an average value B ≈ 3 μG (Han et al. 2006). The possible detection of Faraday rotation of linearly polarized photons emitted by high-redshift quasars (Kronberg et al. 2008) suggests similar magnetic fields are present in foreground galaxies with redshifts z &gt; 1. As Faraday rotation alone, however, determines neither the magnitude nor the redshift of the magnetic field, the strength of galactic magnetic fields at redshifts z &gt; 0 remains uncertain.Here we report a measurement of a magnetic field of B ≈ 84 μG in a galaxy at z =0.692, using the same Zeeman-splitting technique that revealed an average value of B = 6 μG in the neutral interstellar gas of our Galaxy (Heiles et al. 2004). This is unexpected, as the leading theory of magnetic field generation, the mean-field dynamo model, predicts large-scale magnetic fields to be weaker in the past, rather than stronger (Parker 1970).The full text of this paper was published in Nature (Wolfe et al. 2008).