Yun, Min

Job Title

Professor, Department of Astronomy

Last Name

Yun

First Name

Min

Discipline

Astrophysics and Astronomy

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UNVEILING THE NATURE OF SUBMILLIMETER GALAXY SXDF 850.6 (vol 711, pg 974, 2010)
(2010-01) Hatsukade, B; Iono, D; Yoshikawa, T; Akiyama, M; Dunlop, JS; Ivison, RJ; Peck, AB; Ikarashi, S; Biggs, A; Ezawa, H; Hanami, H; Ho, P; Hughes, DH; Kawabe, R; Kohno, K; Matsushita, S; Nakanishi, K; Padilla, N; Petitpas, G; Tamura, Y; Wagg, J; Wilner, DJ; Wilson, GW; Yamada, T; Yun, Min
We present an 880 μm Submillimeter Array (SMA) detection of the submillimeter galaxy SXDF 850.6. SXDF 850.6 is a bright source (S 850 μm = 8 mJy) detected in the SCUBA Half Degree Extragalactic Survey and has multiple possible radio counterparts in its deep radio image obtained at the VLA. Our new SMA detection finds that the submillimeter emission coincides with the brightest radio emission that is found ~8'' north of the coordinates determined from SCUBA. Despite the lack of detectable counterparts in deep UV/optical images, we find a source at the SMA position in near-infrared and longer wavelength images. We perform spectral energy distribution (SED) model fits to UV-optical-IR photometry (u, B, V, R, i', z', J, H, K, 3.6 μm, 4.5 μm, 5.8 μm, and 8.0 μm) and to submillimeter-radio photometry (850 μm, 880 μm, 1100 μm, and 21 cm) independently, and we find both are well described by starburst templates at a redshift of z 2.2 ± 0.3. The best-fit parameters from the UV-optical-IR SED fit are a redshift of z = 1.87+0.15 –0.07, a stellar mass of M = 2.5+2.2 –0.3 × 1011 M , an extinction of AV = 3.0+0.3 –1.0 mag, and an age of 720+1880 –210 Myr. The submillimeter-radio SED fit provides a consistent redshift of z ~ 1.8-2.5, an IR luminosity of L IR = (7-26) ×1012 L , and a star formation rate of 1300-4500 M yr–1. These results suggest that SXDF 850.6 is a mature system already having a massive amount of old stellar population constructed before its submillimeter bright phase and is experiencing a dusty starburst, possibly induced by major mergers.
SEYFERT'S SEXTET: A SLOWLY DISSOLVING STEPHAN'S QUINTET?
(2008-01) Durbala, A; del Olmo, A; Yun, Min; Rosado, M; Sulentic, JW; Plana, H; Iovino, A; Perea, J; Verdes-Montenegro, L; Fuentes-Carrera, I
We present a multiwavelength study of the highly evolved compact galaxy group known as Seyfert's Sextet (HCG79: SS). We interpret SS as a 2-3 Gyr more evolved analog of Stephan's Quintet (HCG92: SQ). We postulate that SS formed by sequential acquisition of 4-5 primarily late-type field galaxies. Four of the five galaxies show an early-type morphology which is likely the result of secular evolution driven by gas stripping. Stellar stripping has produced a massive/luminous halo and embedded galaxies that are overluminous for their size. These are interpreted as remnant bulges of the accreted spirals. H79d could be interpreted as the most recent intruder, being the only galaxy with an intact interstellar medium (ISM) and uncertain evidence for tidal perturbation. In addition to stripping activity we find evidence for past accretion events. H79b (NGC6027) shows a strong counter-rotating emission line component interpreted as an accreted dwarf spiral. H79a shows evidence for an infalling component of gas representing feedback or possible cross-fueling by H79d. The biggest challenge to this scenario involves the low gas fraction in the group. If SS formed from normal field spirals then much of the gas is missing. Finally, despite its advanced stage of evolution, we find no evidence for major mergers and infer that SS (and SQ) are telling us that such groups coalesce via slow dissolution.
Westerbork ultra-deep survey of HI at z=0.2
(2010-01) Verheijen, M; Deshev, B; van Gorkom, J; Poggianti, B; Chung, A; Cybulski, R; Dawarakanath, KS; Montero-Castano, M; Morrison, G; Schiminovich, D; Szomoru, A; Yun, Min
In this contribution, we present some preliminary observational results from the completed ultra-deep survey of 21cm emission from neutral hydrogen at redshifts z=0.164-0.224 with the Westerbork Synthesis Radio Telescope. In two separate fields, a total of 160 individual galaxies has been detected in neutral hydrogen, with HI masses varying from 1.1x10^9 to 4.0x10^10 Msun. The largest galaxies are spatially resolved by the synthesized beam of 23x37 arcsec^2 while the velocity resolution of 19 km/s allowed the HI emission lines to be well resolved. The large scale structure in the surveyed volume is traced well in HI, apart from the highest density regions like the cores of galaxy clusters. All significant HI detections have obvious or plausible optical counterparts which are usually blue late-type galaxies that are UV-bright. One of the observed fields contains a massive Butcher-Oemler cluster but none of the associated blue galaxies has been detected in HI. The data suggest that the lower-luminosity galaxies at z=0.2 are more gas-rich than galaxies of similar luminosities at z=0, pending a careful analysis of the completeness near the detection limit. Optical counterparts of the HI detected galaxies are mostly located in the 'blue cloud' of the galaxy population although several galaxies on the 'red sequence' are also detected in HI. These results hold great promise for future deep 21cm surveys of neutral hydrogen with MeerKAT, APERTIF, ASKAP, and ultimately the Square Kilometre Array.
The NAture of the Faint Far-Infrared Extragalactic Source Population: Optical/NIR and Radio Follow-Up Observationts of ISOPHOT Deep-Field Sources using the Keck, Subaru, and VLA Telescopes.
(2002-01) Kakazu, Y; Sanders, DB; Joseph, RD; Cowie, LL; Murayama, T; Taniguchi, Y; Veilleux, S; Yun, Min; Kawara, K; Sofue, Y; Sato, Y; Okuda, H; Wakamatsu, K; Matsumoto, T; Matsuhara, H
In order to search for obscured objects at high redshifts, we have made deep far-infrared (FIR) deep survey in the Lockman Hole using ISOPHOT onboard ISO (Kawara et al. 1998, A&A, 336, L9). In this survey several tens of FIR sources have been found at 95micron and 175micron. Here we present results of optical and NIR spectroscopic followup observations performed at the W. M.Keck Observatory.
The large asymmetric HI envelope of the isolated galaxy NGC 864 (CIG 96)
(2005-01) Espada, D; Bosma, A; Verdes-Montenegro, L; Athanassoula, E; Leon, S; Sulentic, J; Yun, Min
We present an HI synthesis imaging study of NGC 864 (CIG 96), a spiral galaxy well isolated from similarly sized companions, yet presenting an intriguing asymmetry in its integral HI spectrum. The asymmetry in the HI profile is associated with a strong kinematical perturbation in the gaseous envelope of the galaxy, where at one side the decay of the rotation curve is faster than Keplerian. We detect a small (M(HI) = 5 106 ) galaxy with a faint optical counterpart at ~80 kpc projected distance from NGC 864. This galaxy is probably not massive enough to have caused the perturbations in NGC 864. We discuss alternatives, such as the accretion of a gaseous companion at a radial velocity lower than the maximum.
AN INVESTIGATION OF THE DUST CONTENT IN THE GALAXY PAIR NGC 1512/1510 FROM NEAR-INFRARED TO MILLIMETER WAVELENGTHS
(2010-01) Liu, GL; Calzetti, D; Yun, Min; Wilson, GW; Draine, BT; Scott, K; Austermann, J; Perera, T; Hughes, D; Aretxaga, I; Kohno, K; Kawabe, R; Ezawa, H
We combine new ASTE/AzTEC 1.1 mm maps of the galaxy pair NGC 1512/1510 with archival Spitzer IRAC and MIPS images covering the wavelength range 3.6-160 μm from the SINGS project. The availability of the 1.1 mm map enables us to measure the long-wavelength tail of the dust emission in each galaxy, and in sub-galactic regions in NGC 1512, and to derive accurate dust masses. The two galaxies form a pair consisting of a large, high-metallicity spiral (NGC 1512) and a low-metallicity, blue compact dwarf (NGC 1510), which we use to compare similarities and contrast differences. Using the models of Draine and Li, the derived total dust masses are (2.4 ± 0.6) × 107 M and (1.7 ± 3.6) × 105 M for NGC 1512 and NGC 1510, respectively. The derived ratio of dust mass to H I gas mass for the galaxy pair, 0.0034, is much lower (by at least a factor of 3) than expected, as previously found by Draine et al. In contrast, regions within NGC 1512, specifically the central region and the arms, do not show such unusually low ratios; furthermore, the dust-to-gas ratio is within expectations for NGC 1510. These results suggest that a fraction of the H I included in the determination of the ratio of the NGC 1512/NGC 1510 pair is not associated with the star-forming disks/regions of either galaxy. Using the dust masses derived from the models of Draine & Li as references, we perform simple two-temperature modified blackbody fits to the far-infrared/millimeter data of the two galaxies and the sub-regions of NGC 1512, in order to derive and compare the dust masses associated with warm and cool dust temperature components. As generally expected, the warm dust temperature of the low-metallicity, low-mass NGC 1510 (Tw ~ 36 K) is substantially higher than the corresponding warm temperature of the high-metallicity spiral NGC 1512 (Tw ~ 24 K). In both galaxies (albeit with a large uncertainty for NGC 1510), our fits indicate that a substantial fraction (>93%) of the total dust mass is in a cool dust component, with temperatures ~14-16 K for NGC 1512 and ~15-24 K for NGC 1510. This result is similar to what is determined for a few other nearby galaxies. In contrast, the warm dust component in the sub-galactic regions of NGC 1512 represents a much larger fraction of the total dust content, in agreement with the fact that all three regions have higher specific star formation rates than the average in the galaxy; in the center, the warm dust represents about 40% of the total, while in the arms the fractions are close to ~20%.
Radio-to-Far-Infrared Spectral Energy Distribution and Photometric Redshifts for Dusty Starburst Galaxies
(2002-01) Yun, Min; Carilli, CLC
As a logical next step in improving the radio-to-submillimeter spectral index as a redshift indicator, we have investigated a technique of using the entire radio-to-far-infrared spectral energy distribution (SED) for deriving photometric redshifts for dusty starburst galaxies at high redshift. A dusty starburst SED template is developed from the theoretical understanding of various emission mechanisms related to massive star formation processes, and the template parameters are selected by examining the observed properties of 23 IR-selected starburst galaxies: Td = 58 K, β = 1.35, and fnth = 1. The major improvement in using this template SED for deriving photometric redshifts is the significant reduction in redshift uncertainty over the spectral index technique, particularly at higher redshifts. Intrinsic dispersion in the radio and far-infrared SEDs as well as absolute calibration and measurement errors contribute to the overall uncertainty of the technique. The derived photometric redshifts for five submillimeter galaxies with known redshifts agree well with their spectroscopic redshifts within the estimated uncertainty. Photometric redshifts for seven submillimeter galaxies without known spectroscopic redshifts (HDF 850.1, CUDSS 14.1, Lockman 850.1, SMM J00266+1708, SMM J09429+4658, SMM J14009+0252, and FIRBACK J1608+5418) are derived.
Discovery of Molecular Gas in the Outflow and Tidal Arms around M82
(2001-01) Taylor, CL; Walter, F; Yun, Min
We present the first fully sampled map of 12CO (1-0) emission from M82 covering the entire galaxy. Our map contains an ~12 × 15 kpc2 area. We find that extraplanar CO emission, previously reported at short distances above the galactic plane, extends to heights of up to 6 kpc above the disk. Some of this emission is associated with tidal arms seen in H I, implying either that M82 contained substantial amounts of molecular gas in the outer disk or that molecular gas formed after the tidal features. CO emission along the direction of the outflow extends to distances of ~3 kpc above and below the disk. At this distance, the line is shifted in velocity ~100 km s-1 and has the same sense as the galactic outflow from the central starburst. This implies that molecular gas may be entrained into the outflow.
The Bolocam 1.1 mm Lockman Hole Galaxy Survey: SHARC II 350 μm Photometry and Implications for Spectral Models, Dust Temperatures, and Redshift Estimation
(2006-01) Laurent, GT; Glenn, J; Egami, E; Rieke, GH; Ivison, RJ; Yun, Min; Aguirre, JE; Maloney, PR; Haig, D
We present 350 μm photometry of all 17 galaxy candidates in the Lockman Hole detected in a 1.1 mm Bolocam survey. Several of the galaxies were previously detected at 850 μm, at 1.2 mm, in the infrared by Spitzer, and in the radio. Nine of the Bolocam galaxy candidates were detected at 350 μm, and two new candidates were serendipitously detected at 350 μm (bringing the total in the literature detected in this way to three). Five of the galaxies have published spectroscopic redshifts, enabling investigation of the implied temperature ranges and a comparison of photometric redshift techniques. For z 2.5 thermally emitting galaxies, λ = 350 μm lies near the spectral energy distribution peak. Thus, luminosities can be measured without extrapolating to the peak from detection wavelengths of λ ≥ 850 μm. Characteristically, the galaxy luminosities lie in the range 1.0-1.2 × 1013 L, with dust temperatures in the range 40-70 K, depending on the choice of spectral index and wavelength of unit optical depth. The implied dust masses are × 108 M. We find that the far-infrared to radio relation for star-forming ULIRGs systematically overpredicts the radio luminosities and overestimates redshifts on the order of Δz 1, whereas redshifts based on either submillimeter data alone or the 1.6 μm stellar bump and PAH features are more accurate.
A massive protocluster of galaxies at a redshift of z ≈ 5.3
(2011-01) Capak, PL; Riechers, D; Scoville, NZ; Carilli, C; Cox, P; Neri, R; Robertson, B; Savato, M; Schinnerer, E; Yan, L; Wilson, GW; Yun, Min; Civano, F; Elvis, M; Karim, A; Mobasher, B; Staguhn, JG
Massive clusters of galaxies have been found that date from as early as 3.9 billion years1 (3.9 Gyr; z = 1.62) after the Big Bang, containing stars that formed at even earlier epochs2, 3. Cosmological simulations using the current cold dark matter model predict that these systems should descend from ‘protoclusters’—early overdensities of massive galaxies that merge hierarchically to form a cluster4, 5. These protocluster regions themselves are built up hierarchically and so are expected to contain extremely massive galaxies that can be observed as luminous quasars and starbursts4, 5, 6. Observational evidence for this picture, however, is sparse because high-redshift protoclusters are rare and difficult to observe6, 7. Here we report a protocluster region that dates from 1 Gyr (z = 5.3) after the Big Bang. This cluster of massive galaxies extends over more than 13 megaparsecs and contains a luminous quasar as well as a system rich in molecular gas8. These massive galaxies place a lower limit of more than 4 × 1011 solar masses of dark and luminous matter in this region, consistent with that expected from cosmological simulations for the earliest galaxy clusters4, 5, 7.