Yun, Min

Job Title

Professor, Department of Astronomy

Last Name

Yun

First Name

Min

Discipline

Astrophysics and Astronomy

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Now showing 1 - 10 of 82

AzTEC half square degree survey of the SHADES fields - I. Maps, catalogues and source counts
(2010-01-01) Austermann, JE; Yun, Min
We present the first results from the largest deep extragalactic mm-wavelength survey undertaken to date. These results are derived from maps covering over 0.7 deg2, made at λ= 1.1 mm, using the AzTEC continuum camera mounted on the James Clerk Maxwell Telescope. The maps were made in the two fields originally targeted at λ= 850 μm with the Submillimetre Common-User Bolometer Array (SCUBA) in the SCUBA Half-Degree Extragalactic Survey (SHADES) project, namely the Lockman Hole East (mapped to a depth of 0.9–1.3 mJy rms) and the Subaru/XMM–Newton Deep Field (mapped to a depth of 1.0–1.7 mJy rms). The wealth of existing and forthcoming deep multifrequency data in these two fields will allow the bright mm source population revealed by these new wide-area 1.1 mm images to be explored in detail in subsequent papers. Here, we present the maps themselves, a catalogue of 114 high-significance submillimetre galaxy detections, and a thorough statistical analysis leading to the most robust determination to date of the 1.1 mm source number counts. These new maps, covering an area nearly three times greater than the SCUBA SHADES maps, currently provide the largest sample of cosmological volumes of the high-redshift Universe in the mm or sub-mm. Through careful comparison, we find that both the Cosmic Evolution Survey (COSMOS) and the Great Observatories Origins Deep Survey (GOODS) North fields, also imaged with AzTEC, contain an excess of mm sources over the new 1.1 mm source-count baseline established here. In particular, our new AzTEC/SHADES results indicate that very luminous high-redshift dust enshrouded starbursts (S1.1mm > 3 mJy) are 25–50 per cent less common than would have been inferred from these smaller surveys, thus highlighting the potential roles of cosmic variance and clustering in such measurements. We compare number count predictions from recent models of the evolving mm/sub-mm source population to these sub-mm bright galaxy surveys, which provide important constraints for the ongoing refinement of semi-analytic and hydrodynamical models of galaxy formation, and find that all available models overpredict the number of bright submillimetre galaxies found in this survey.
The Evolution of Galaxy Disks in Dense Environments - Lessons from Compact Galaxy Groups
(2008-01-01) Rasmussen, J; Ponman, TJ; Verdes-Montenegro, L; Yun, Min; Borthakur, S
Disk galaxies in compact galaxy groups exhibit a remarkable shortfall of neutral hydrogen compared to both isolated spirals and spirals in more loose groups, but the origin of this HI deficiency remains unclear. Based on a sample of highly HI deficient compact galaxy groups, here updated to also include HCG 58 and HCG 93, we summarise the first results of a multi-wavelength campaign aimed at understanding the processes responsible for modifying the HI content of galaxy disks in these environments. While tidal stripping, ram pressure stripping by hot intragroup gas, and star-formation induced strangulation could individually be affecting the ISM in some of the group members, these processes each face specific difficulties in explaining the inferred deficiency of HI for the sample as a whole. A complete picture of the mechanisms driving the ISM evolution in the disk galaxies of these groups has thus yet to emerge, but promising avenues for further progress in this field are briefly discussed on the basis of the present sample.
A GREEN BANK TELESCOPE SURVEY FOR H I 21 cm ABSORPTION IN THE DISKS AND HALOS OF LOW-REDSHIFT GALAXIES*
(2011-01-01) Borthakur, S; Tripp, TM; Yun, Min; Bowen, DV; Meiring, JD; York, DG; Momjian, E
We present an H I 21 cm absorption survey with the Green Bank Telescope (GBT) of galaxy-quasar pairs selected by combining galaxy data from the Sloan Digital Sky Survey (SDSS) and radio sources from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. Our sample consists of 23 sight lines through 15 low-redshift foreground galaxy-background quasar pairs with impact parameters ranging from 1.7 kpc up to 86.7 kpc. We detected one absorber in the GBT survey from the foreground dwarf galaxy, GQ1042+0747, at an impact parameter of 1.7 kpc and another possible absorber in our follow-up Very Large Array (VLA) imaging of the nearby foreground galaxy UGC 7408. The line widths of both absorbers are narrow (FWHM of 3.6 and 4.8km s–1). The absorbers have sub-damped Lyα column densities, and most likely originate in the disk gas of the foreground galaxies. We also detected H I emission from three foreground galaxies including UGC 7408. Although our sample contains both blue and red galaxies, the two H I absorbers as well as the H I emissions are associated with blue galaxies. We discuss the physical conditions in the 21 cm absorbers and some drawbacks of the large GBT beam for this type of survey.
THE AzTEC/SMA INTERFEROMETRIC IMAGING SURVEY OF SUBMILLIMETER-SELECTED HIGH-REDSHIFT GALAXIES
(2009-01-01) Younger, JD; Fazio, GG; Huang, JS; Yun, Min; Wilson, GW; Ashby, MLN; Gurwell, MA; Peck, AB; Petitpas, GR; Wilner, DJ; Hughes, DH; Aretxaga, I; Kim, S; Scott, KS; Austermann, J; Perera, T; Lowenthal, JD
We present results from a continuing interferometric survey of high-redshift submillimeter galaxies (SMGs) with the Submillimeter Array, including high-resolution (beam size ~2 arcsec) imaging of eight additional AzTEC 1.1 mm selected sources in the COSMOS field, for which we obtain six reliable (peak signal-to-noise ratio (S/N) >5 or peak S/N >4 with multiwavelength counterparts within the beam) and two moderate significance (peak S/N >4) detections. When combined with previous detections, this yields an unbiased sample of millimeter-selected SMGs with complete interferometric follow up. With this sample in hand, we (1) empirically confirm the radio-submillimeter association, (2) examine the submillimeter morphology—including the nature of SMGs with multiple radio counterparts and constraints on the physical scale of the far infrared—of the sample, and (3) find additional evidence for a population of extremely luminous, radio-dim SMGs that peaks at higher redshift than previous, radio-selected samples. In particular, the presence of such a population of high-redshift sources has important consequences for models of galaxy formation—which struggle to account for such objects even under liberal assumptions—and dust production models given the limited time since the big bang.
The Canada-UK deep submillimeter survey. VII. Optical and near-infrared identifications for the 14 hour field
(2003-01-01) Webb, TMA; Lilly, SJ; Clements, DL; Eales, S; Yun, Min; Brodwin, M; Dunne, L; Gear, WK
We present the multiwavelength identifications for 23 sources in the Canada-UK Deep Submillimeter Survey (CUDSS) 14h field. The identifications have been selected on the basis of radio and near-infrared data, and we argue that, to our observational limits, both are effective at selecting the correct counterparts of the SCUBA sources. We discuss the properties of these identifications and find that they are very red in near-infrared color, with many classified as extremely red objects, and show disturbed morphologies. Using the entire CUDSS catalog of 50 sources, we use a combination of spectroscopic redshifts (four objects), 1.4 GHz : 850 μm flux ratio redshift estimates (10 objects), and redshift lower limits based on nondetections at 1.4 GHz (the rest of the sample) to estimate a lower limit on the median redshift of the population of zmed > 1.4. Working from simple models and using the properties of the secure identifications, we discuss general and tentative constraints on the redshift distribution and the expected colors and magnitudes of the entire population.
AzTEC Millimetre Survey of the COSMOS Field: I. Data Reduction and Source Catalogue
(2008-01-01) Scott, K. S.; Austermann, J. E.; Perera, T. A.; Wilson, G. W.; Aretxaga, I.; Bock, J. J.; Hughes, D. H.; Kang, Y.; Kim, S.; Mauskopf, P. D.; Sanders, D. B.; Scoville, N.; Yun, Min
We present a 1.1 mm wavelength imaging survey covering 0.3 deg2 in the COSMOS field. These data, obtained with the AzTEC continuum camera on the James Clerk Maxwell Telescope, were centred on a prominent large-scale structure overdensity which includes a rich X-ray cluster at z≈ 0.73. A total of 50 mm-galaxy candidates, with a significance ranging from 3.5 to 8.5σ, are extracted from the central 0.15 deg2 area which has a uniform sensitivity of ∼1.3 mJy beam−1. 16 sources are detected with S/N ≥ 4.5, where the expected false-detection rate is zero, of which a surprisingly large number (9) have intrinsic (deboosted) fluxes ≥5 mJy at 1.1 mm. Assuming the emission is dominated by radiation from dust, heated by a massive population of young, optically obscured stars, then these bright AzTEC sources have far-infrared luminosities >6 × 1012 L⊙ and star formation rates >1100 M⊙ yr−1. Two of these nine bright AzTEC sources are found towards the extreme peripheral region of the X-ray cluster, whilst the remainder are distributed across the larger scale overdensity. We describe the AzTEC data reduction pipeline, the source-extraction algorithm, and the characterization of the source catalogue, including the completeness, flux deboosting correction, false-detection rate and the source positional uncertainty, through an extensive set of Monte Carlo simulations. We conclude with a preliminary comparison, via a stacked analysis, of the overlapping MIPS 24-μm data and radio data with this AzTEC map of the COSMOS field.
A complete view of galaxy evolution: panchromatic luminosity functions and the generation of metals
(2009-01-01) Blain, AW; Armus, L; Bertoldi, F; Bock, J; Bradford, M; Dowell, CD; Glenn, J; Goldsmith, P; Harwit, M; Helou, G; Smith, JD; Soifer, BT; Stacey, G; Vieira, J; Yun, Min; Zmuidzinas, J
When and how did galaxies form and their metals accumulate? Over the last decade, this has moved from an archeological question to a live investigation: there is now a broad picture of the evolution of galaxies in dark matter halos: their masses, stars, metals and supermassive blackholes. Galaxies have been found and studied in which these formation processes are taking place most vigorously, all the way back in cosmic time to when the intergalactic medium (IGM) was still largely neutral. However, the details of how and why the interstellar medium (ISM) in distant galaxies cools, is processed, recycled and enriched in metals by stars, and fuels active galactic nuclei (AGNs) remain uncertain. In particular, the cooling of gas to fuel star formation, and the chemistry and physics of the most intensely active regions is hidden from view at optical wavelengths, but can be seen and diagnosed at mid- & far-infrared (IR) wavelengths. Rest-frame IR observations are important first to identify the most luminous, interesting and important galaxies, secondly to quantify accurately their total luminosity, and finally to use spectroscopy to trace the conditions in the molecular and atomic gas out of which stars form. In order to map out these processes over the full range of environments and large-scale structures found in the universe - from the densest clusters of galaxies to the emptiest voids - we require tools for deep, large area surveys, of millions of galaxies out to z~5, and for detailed follow-up spectroscopy. The necessary tools can be realized technically. Here, we outline the requirements for gathering the crucial information to build, validate and challenge models of galaxy evolution.
COLOR-MAGNITUDE RELATION AND MORPHOLOGY OF LOW-REDSHIFT ULIRGs IN SLOAN DIGITAL SKY SURVEY
(2010-01-01) Chen, Y; Lowenthal, JD; Yun, Min
We present color-magnitude and morphological analysis of 54 low-redshift ultraluminous infrared galaxies (ULIRGs; 0.018 < z < 0.265 with z median = 0.151), a subset of the Infrared Astronomical Satellite 1 Jy sample, in the Sloan Digital Sky Survey (SDSS). The ULIRGs are both bright and blue: they are on average 1 mag brighter in than the SDSS galaxies within the same redshift range, and 0.2 mag bluer in 0.1 g – 0.1 r. They form a group in the color-magnitude diagram distinct from both the red sequence and the blue cloud formed by the SDSS galaxies: 24 out of the 52 unsaturated objects (~46%) lie outside the 90% level number density contour of the SDSS galaxies. The majority (47, or ~87%) have the colors typical of the blue cloud, and only four (~7%) sources are located in the red sequence. While ULIRGs are popularly thought to be precursors to a QSO phase, we find few (three, or ~6%) in the "green valley" where the majority of the X-ray- and IR-selected active galactic nuclei (AGNs) are found. Moreover, none of the AGN-host ULIRGs are found in the green valley. For the 14 previously spectroscopic identified AGNs (~28%), we perform point-spread function subtractions and find that on average the central point sources contribute less than one-third to the total luminosity, and that their high optical luminosities and overall blue colors are apparently the result of star formation activity of the host galaxies. Visual inspection of the SDSS images reveals a wide range of morphologies including many close pairs, tidal tails, and otherwise disturbed profiles, in strong support of previous studies and the general view of ULIRGs as major mergers of gas-rich disk galaxies. A detailed morphology analysis using Gini and M 20 coefficients shows that slightly less than one-half (~42% in g band) of the ULIRGs are located in the merger region defined by morphology studies of local galaxies, while the remaining sources are located in the region of late-type and irregular galaxies. The heterogeneous distribution of ULIRGs in the G-M 20 space is qualitatively consistent with the results found by numerical simulations of disk-disk mergers, and our study also shows that the measured morphological parameters are systematically affected by the signal-to-noise ratio and thus the merging galaxies can appear in various regions of the G-M 20 parameter space. We briefly discuss the origins of the uncertainties and note that the morphology measurements should be implemented with caution for low physical resolution images. In general, our results reinforce the view that ULIRGs contain young stellar populations and are mergers in progress, but we do not observe the concentration of ULIRGs/AGN in the green valley as found by other studies. Our study provides a uniform comparison sample for studying dusty starbursts at higher redshifts such as Spitzer MIPS 24 μm-selected ULIRGs at z = 1-2 or submillimeter galaxies.
The Bolocam 1.1 mm Lockman Hole Galaxy Survey: SHARC II 350 μm Photometry and Implications for Spectral Models, Dust Temperatures, and Redshift Estimation
(2006-01-01) 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.
First generation continuum cameras for the Large Millimeter telescope
(2004-01-01) Wilson, GW; Austermann, J; Logan, DW; Yun, Min
The Large Millimeter telescope (LMT) is a 50 m diameter telescope currently under construction in Mexico. We describe the first generation continuum instruments for the LMT - BOLOCAM II, a 144 pixel array receiver, and SPEED, a 4 pixel array of frequency selective bolometers. Together, these two instruments form a complementary set of continuum receivers designed for efficient mapping and source follow-up at mm-wavelengths. An overview of the instruments, the telescope, and the key initial science is given.