Kyuseok Oh

BAR EFFECTS ON CENTRAL STAR FORMATION AND ACTIVE GALACTIC NUCLEUS ACTIVITY

Galactic bars are often suspected to be channels of gas inflow to the galactic center and to trigger central star formation and active galactic nucleus (AGN) activity. However, the current status on this issue based on empirical studies is unsettling, especially regarding AGNs. We investigate this question based on the Sloan Digital Sky Survey Data Release 7. From the nearby (0.01 < z < 0.05) bright (M r < –19) database, we have constructed a sample of 6658 relatively face-on late-type galaxies through visual inspection. We found 36% of them to have a bar. Bars are found to be more common in galaxies with earlier morphology. This makes sample selection critical. Parameter-based selections would miss a large fraction of barred galaxies of early morphology. Bar effects on star formation or AGNs are difficult to understand properly because multiple factors (bar frequency, stellar mass, black hole mass, gas contents, etc.) seem to contribute to them in intricate manners. In the hope of breaking these degeneracies, we inspect bar effects for fixed galaxy properties. Bar effects on central star formation seem higher in redder galaxies. Bar effects on AGNs on the other hand are higher in bluer and less massive galaxies. These effects seem more pronounced with increasing bar length. We discuss possible implications in terms of gas contents, bar strength, bar evolution, fueling timescale, and the dynamical role of supermassive black hole.

Imaging of tuberculous disease involving breast

Abstract. The aim of our study was to evaluate radiologic findings of the tuberculosis involving breast. We evaluated the radiologic features of 17 patients (18 lesions) with tuberculous disease involving the breast. The radiologic examinations, including mammography (16 patients), ultrasonography (12 patients), and Gd-DTPA-enhanced dynamic MRI (6 patients), were analyzed. Mammographic findings included mass (12 of 17 lesions), calcification (3 of 17 lesions), asymmetric density with spiculated margin (5 of 17 lesions), and axillary lymph node enlargement (8 of 17 lesions). On ultrasonography, a smooth bordered mass (7 of 13 lesions) with thin boundary (7 of 13 lesions) and heterogeneous, intermediate internal echoes (9 of 13 lesions) were most commonly demonstrated. On Gd-DTPA-enhanced dynamic MRI, 3 lesions showed significant enhancement at the first minute after injection (3 of 7 lesions). The maximun enhancing amount was greater than 500 normalized units, and the enhancing pattern was smooth or irregular ring appearance. Breast involvement with tuberculosis is rare but should be considered in the differential diagnosis of a woman living in an endemic area or when extramammary foci of tuberculosis are present. A multimodality imaging approach with clinical evaluation will help to establish the diagnosis of tuberculosis involving breast.

The search for active black holes in nearby low-mass galaxies using optical and mid-IR data

We investigated AGN activity in low-mass galaxies, an important regime that can shed light onto BH formation and evolution, and their interaction with their host galaxies. We identified 336 AGN candidates from a parent sample of

BAT AGN spectroscopic survey–II. X-ray emission and high-ionization optical emission lines

\sim 48,000

CHANDRA OBSERVATIONS OF GALAXY ZOO MERGERS: FREQUENCY OF BINARY ACTIVE NUCLEI IN MASSIVE MERGERS

nearby low-mass galaxies (

A NEW CATALOG OF TYPE 1 AGNs AND ITS IMPLICATIONS ON THE AGN UNIFIED MODEL

M_{\rm \star} \leq 10^{9.5}M_\odot

BAT AGN Spectroscopic Survey. I. Spectral Measurements, Derived Quantities, and AGN Demographics

,

The close environments of accreting massive black holes are shaped by radiative feedback

z < 0.1

Determining the radio active galactic nuclei contribution to the radio–far-infrared correlation using the black hole Fundamental Plane relation

) in the SDSS. We selected the AGN using the classical BPT diagram, a similar optical emission line diagnostic based on the HeII

BAT AGN Spectroscopic Survey (BASS) – VI. The ΓX–L/LEdd relation

\lambda