1,690 research outputs found

    Simulating galaxies in the reionization era with FIRE-2: morphologies and sizes

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    We study the morphologies and sizes of galaxies at z>5 using high-resolution cosmological zoom-in simulations from the Feedback In Realistic Environments project. The galaxies show a variety of morphologies, from compact to clumpy to irregular. The simulated galaxies have more extended morphologies and larger sizes when measured using rest-frame optical B-band light than rest-frame UV light; sizes measured from stellar mass surface density are even larger. The UV morphologies are usually dominated by several small, bright young stellar clumps that are not always associated with significant stellar mass. The B-band light traces stellar mass better than the UV, but it can also be biased by the bright clumps. At all redshifts, galaxy size correlates with stellar mass/luminosity with large scatter. The half-light radii range from 0.01 to 0.2 arcsec (0.05-1 kpc physical) at fixed magnitude. At z>5, the size of galaxies at fixed stellar mass/luminosity evolves as (1+z)^{-m}, with m~1-2. For galaxies less massive than M_star~10^8 M_sun, the ratio of the half-mass radius to the halo virial radius is ~10% and does not evolve significantly at z=5-10; this ratio is typically 1-5% for more massive galaxies. A galaxy's "observed" size decreases dramatically at shallower surface brightness limits. This effect may account for the extremely small sizes of z>5 galaxies measured in the Hubble Frontier Fields. We provide predictions for the cumulative light distribution as a function of surface brightness for typical galaxies at z=6.Comment: 11 pages, 11 figures, resubmitted to MNRAS after revision for referee's comment

    Formation of Globular Cluster Candidates in Merging Proto-galaxies at High Redshift: A View from the FIRE Cosmological Simulations

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    Using a state-of-the-art cosmological simulation of merging proto-galaxies at high redshift from the FIRE project, with explicit treatments of star formation and stellar feedback in the interstellar medium, we investigate the formation of star clusters and examine one of the formation hypothesis of present-day metal-poor globular clusters. We find that frequent mergers in high-redshift proto-galaxies could provide a fertile environment to produce long-lasting bound star clusters. The violent merger event disturbs the gravitational potential and pushes a large gas mass of ~> 1e5-6 Msun collectively to high density, at which point it rapidly turns into stars before stellar feedback can stop star formation. The high dynamic range of the reported simulation is critical in realizing such dense star-forming clouds with a small dynamical timescale, t_ff <~ 3 Myr, shorter than most stellar feedback timescales. Our simulation then allows us to trace how clusters could become virialized and tightly-bound to survive for up to ~420 Myr till the end of the simulation. Because the cluster's tightly-bound core was formed in one short burst, and the nearby older stars originally grouped with the cluster tend to be preferentially removed, at the end of the simulation the cluster has a small age spread.Comment: 14 pages, 14 figures, Accepted for publication in the Monthly Notices of the Royal Astronomical Society, High-resolution version of this article also available at http://www.jihoonkim.org/index/research.html#g

    Peran Lsm dalam Program Pendampingan Anak Jalanan Menuju Ketahanan Sosial Keluarga (Study Kasus Lsm Ppap Seroja di Kota Surakarta)

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    Bachtiar Rofi\u27i. “PERAN LSM DALAM PROGRAM PENDAMPINGAN ANAK JALANAN MENUJU KETAHANAN KELUARGA (Study Kasus LSM PPAP Seroja Di Kota Surakarta)”.Skripsi. Surakarta: Fakultas Keguruan dan Ilmu Pendidikan. Universitas Sebelas Maret 2017. Siti Rochani dan Siany Indria Liestyasari. Penelitian betujuan untuk mengetahui: (1) untuk mengidentifikasi bentuk pendampingan LSM yang mengarah pada ketahanan sosial keluarga anak jalanan; (2) untuk mengetahui kendala LSM dalam penerapan pendampingan orangtua dan anak jalanan di Kota Surakarta; (3) Untuk mengetahui dampak dari pola pendampingan LSM terhadap orangtua dan anak jalanan di Kota Surakarta.Penelitian ini termasuk dalam jenis penelitian kualitatif dengan pendekatan study kasus.Pengumpulan data berasal dari wawancara, observasi, serta dokumentasi. Wawancara dilakukan dengan enam informan, yang terdiri dari dua pengurus LSM, dua orangtua anak jalanan, dua anak dampingan LSM diantaranya ada yang masih berprofesi sebagai anak jalanan, dan mantan anak jalanan. Penelitian ini mengunakan tekhnik pengambilan informan dengan cara purposive sampling. Dalam melakukan uji validitas data, yang dilakukan yaitu dengan trianggulasi sumber dan trianggulasi metode.Tekhnik analisis data menggunakan analisis interaktif yang terdiri dari pengumpulan data, reduksi data, penyajian data, dan penarikan data (verivikasi data).Hasil penelitian menunjukan: (1) Pendampingan LSM yang mengarah pada ketahanan sosial keluarga anak jalanan adalah (a) aspek pendidikan, (b) aspek ekonomi, (c) aspek kesehatan, (d) aspek agama, (e) aspek komunikasi, (f) aspek hukum; (2) Kendala LSM dalam penerapan pendampingan orangtua dan anak jalanan di Kota Surakarta adalah (a) kendala internal, (b) kendala eksternal (3) Dampak dari pola pendampingan LSM terhadap orangtua dan anak jalanan di Kota Surakarta mencangkup (a) aspek pendidikan, (b) aspek ekonomi, (c) aspek kesehatan, (d) aspek agama, (e) aspek komunikasi, (f) aspek hukum.Kesimpulan penelitian ini adalah bahwa meningkatkan ketahanan sosial keluarga anak jalanan dianggap solusi yang tepat untuk megurangi angka anak jalanan yang ada di Kota Suarakarta. Kata Kunci : Anak Jalanan, Ketahanan Sosial Keluarg

    Star formation histories of dwarf galaxies in the FIRE simulations: dependence on mass and Local Group environment

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    We study star formation histories (SFHs) of 500\simeq500 dwarf galaxies (stellar mass M=105109MM_\ast = 10^5 - 10^9\,M_\odot) from FIRE-2 cosmological zoom-in simulations. We compare dwarfs around individual Milky Way (MW)-mass galaxies, dwarfs in Local Group (LG)-like environments, and true field (i.e. isolated) dwarf galaxies. We reproduce observed trends wherein higher-mass dwarfs quench later (if at all), regardless of environment. We also identify differences between the environments, both in terms of "satellite vs. central" and "LG vs. individual MWvs. isolated dwarf central." Around the individual MW-mass hosts, we recover the result expected from environmental quenching: central galaxies in the "near field" have more extended SFHs than their satellite counterparts, with the former more closely resemble isolated ("true field") dwarfs (though near-field centrals are still somewhat earlier forming). However, this difference is muted in the LG-like environments, where both near-field centrals and satellites have similar SFHs, which resemble satellites of single MW-mass hosts. This distinction is strongest for M=106107MM_\ast = 10^6 - 10^7\,M_\odot but exists at other masses. Our results suggest that the paired halo nature of the LG may regulate star formation in dwarf galaxies even beyond the virial radii of the MW and Andromeda. Caution is needed when comparing zoom-in simulations targeting isolated dwarf galaxies against observed dwarf galaxies in the LG.Comment: Main text: 11 pages, 8 figures; appendices: 4 pages, 4 figures. Submitted to MNRAS; comments welcom

    A Silicon p-i-n detector for a hybrid CMOS imaging system

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    A fully depleted silicon p-i-n image sensor for a very low noise hybrid CMOS imaging system was simulated, fabricated, and electrically characterized. The image sensor was then bonded to the foundry fabricated CMOS circuitry to create the imaging system. SILVACO Atlas was used to simulate the steady state electrical operation of the device as well as the optical response. Revisions were made to an existing mask set to allow the use of both contact and projection lithography in the fabrication process. Significant process improvements were introduced to eliminate needless complexity and reduce leakage current from the previously reported 1.5x10-6 A/cm2 below the goal of 2.2x10-9 A/cm2. Following fabrication of the image sensors, electrical testing was performed to verify diode quality from leakage and lifetime measurements. A lift-off process was developed for thick metal layers used in the bump-bond hybridization process. Daisy-chain test parts were created to characterize the mechanical and electrical connections formed in the hybridization process. Fabricated p-i-n photodiode arrays were diced and hybridized to read-out integrated circuits using a flip-chip bump bond process with indium interconnects. Testing of hybridized devices is currently ongoing

    Hackney, Sheldon: Humanities Chairman Nomination Hearing (1993): News Article 08

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    Rainbow Trout (Oncorhynchus mykiss) Movement and Mortality in the Flat Brook-Roy Catch and Release Section of New Jersey

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    Rainbow trout are a widely distributed species for recreational angling. The state of New Jersey has 14 streams in which the Bureau of Freshwater Fisheries stocks hatchery raised Rainbow Trout. This paper focuses on the Flatbrook-Roy catch and release section of the Big Flat Brook in northwest NJ. From 2012 to 2015, electrofishing surveys conducted by the NJDEP reported significantly less fish within the Flatbrook-Roy catch and release area, compared to the state’s other catch and release area in the South Branch of the Raritan River. This study was designed to investigate and understand the fate of the trout introduced into the Flat Brook-Roy section by looking at their survivorship and movement in and/or out of the catch and release section of the stream. 79 fish were surgically implanted with radio transmitters and introduced into three separate stocking locations from April-September of 2017 and 2018. The data collected across the two years showed that the trout were not traveling outside of the catch and release designated waters. Across the summer months of each year, there was a 100% mortality rate within the sample, all credited to specific mammalian or avian predation events. Between the stocking sites, the trout both stayed longer and survived better at the site with the largest pool dimensions and most in-stream cover. The findings help fisheries management decisions by confirming that the introduced trout do in fact remain within the designated catch and release waters. Future decisions related to fish allocation and fishery regulation should consider stocking sites of adequate size that provide enough cover to increase survivorship and mitigate predation in order to maximize the recreational angling experience
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