Minju Lee

ALMA MULTI-LINE OBSERVATIONS OF THE IR-BRIGHT MERGER VV 114

We present ALMA cycle 0 observations of the molecular gas and dust in the IR-bright mid-stage merger VV114 obtained at 160 - 800 pc resolution. The main aim of this study is to investigate the distribution and kinematics of the cold/warm gas and to quantify the spatial variation of the excitation conditions across the two merging disks. The data contain 10 molecular lines, including the first detection of extranuclear CH3OH emission in interacting galaxies, as well as continuum emission. We map the 12CO(3-2)/12CO(1-0) and the 12CO(1-0)/13CO(1-0) line ratio at 800 pc resolution (in the units of K km/s), and find that these ratios vary from 0.2 - 0.8 and 5 - 50, respectively. Conversely, the 200 pc resolution HCN(4-3)/HCO+(4-3) line ratio shows low values (< 0.5) at a filament across the disks except for the unresolved eastern nucleus which is three times higher (1.34 +/- 0.09). We conclude from our observations and a radiative transfer analysis that the molecular gas in the VV114 system consists of five components with different physical and chemical conditions; i.e., 1) dust-enshrouded nuclear starbursts and/or AGN, 2) wide-spread star forming dense gas, 3) merger-induced shocked gas, 4) quiescent tenuous gas arms without star formation, 5) H2 gas mass of (3.8 +/- 0.7) * 10^7 Msun (assuming a conversion factor of {\alpha}_CO = 0.8 Msun (K km s^-1 pc^2)^-1) at the tip of the southern tidal arm, as a potential site of tidal dwarf galaxy formation.

SXDF–ALMA 2-arcmin2 deep survey: 1.1-mm number counts

We report 1.1-mm number counts revealed with the Atacama Large Millimeter/submillimeter Array (ALMA) in the Subaru/XMM-Newton Deep Survey Field (SXDF). The advent of ALMA enables us to reveal millimeter-wavelength number counts down to the faint end without source confusion. However, previous studies are based on the ensemble of serendipitously detected sources in fields originally targeting different sources and could be biased due to the clustering of sources around the targets. We derive number counts in the flux range of 0.2-2 mJy by using 23 (≥4σ) sources detected in a continuous 2.0-arcmin2 area of the SXDF. The number counts are consistent with previous results within errors, suggesting that the counts derived from serendipitously detected sources are not significantly biased, although there could be field-to-field variation due to the small survey area. By using the best-fitting function of the number counts, we find that ˜40% of the extragalactic background light at 1.1 mm is resolved at S1.1mm > 0.2 mJy.

Spatially Resolved CO SLED of the Luminous Merger Remnant NGC 1614 with ALMA

We present high-resolution (1.”0) Atacama Large Millimeter/submillimeter Array (ALMA) observations of CO (1–0) and CO (2–1) rotational transitions toward the nearby IR-luminous merger NGC 1614 supplemented with ALMA archival data of CO (3–2) and CO (6–5) transitions. The CO (6–5) emission arises from the starburst ring (central 590 pc in radius), while the lower-J CO lines are distributed over the outer disk (~3.3 kpc in radius). Radiative transfer and photon-dominated region (PDR) modeling reveals that the starburst ring has a single warmer gas component with more a intense far-ultraviolet radiation field (n_(H_2) ~ 10^(4.6) Cm^(−3), T_(kin) ~ 42 K, and G_0 ~ 10^(2.7)) relative to the outer disk (N_(H_2) ~ 10^(5.1) cm^(−3), T_(kin) ~ 22 K, and G_0 ~ 10^(0.9)). A two-phase molecular interstellar medium with a warm and cold (>70 and ~19 K) component is also an applicable model for the starburst ring. A possible source for heating the warm gas component is mechanical heating due to stellar feedback rather than PDR. Furthermore, we find evidence for non-circular motions along the north–south optical bar in the lower-J CO images, suggesting a cold gas inflow. We suggest that star formation in the starburst ring is sustained by the bar-driven cold gas inflow and that starburst activities radiatively and mechanically power the CO excitation. The absence of a bright active galactic nucleus can be explained by a scenario where cold gas accumulating on the starburst ring is exhausted as the fuel for star formation or is launched as an outflow before being able to feed to the nucleus.

SXDF-UDS-CANDELS-ALMA 1.5 arcmin2 deep survey

We have conducted 1.1 mm ALMA observations of a contiguous 105″ × 50″ or 1.5 arcmin2 window (achieved by 19 point mosaic) in the SXDF-UDS-CANDELS. We achieved a 5σ sensitivity of 0.28 mJy, giving a flat sensus of dusty star-forming galaxies with LIR ~6 × 1011 L⊙ (if Tdust = 40 K) or SFR ~100 M⊙ yr-1 up to z~10 thanks to the negative K-correction at this wavelength. We detect 5 brightest sources (S/N>6) and 18 low-significant sources (5 > S/N > 4; they may contain spurious detections, though) in the field. We find that these discrete sources are responsible for a faint filamentary emission seen in low-resolution (~30″) heavily confused AzTEC 1.1mm and SPIRE 0.5mm images. One of the 5 brightest ALMA sources is very dark in deep WFC3 and HAWK-I NIR images as well as VLA 1.4 GHz images, demonstrating that deep ALMA imaging can unveil new obscured star-forming galaxy population.

SXDF-ALMA 2 arcmin2 deep survey: Resolving and characterizing the infrared extragalactic background light down to 0.5 mJy

We present a multi-wavelength analysis of five submillimeter sources (S_1.1mm = 0.54-2.02 mJy) that were detected during our 1.1-mm-deep continuum survey in the SXDF-UDS-CANDELS field (2 arcmin^2, 1sigma = 0.055 mJy beam^-1) using the Atacama Large Millimeter/submillimeter Array (ALMA). The two brightest sources correspond to a known single-dish (AzTEC) selected bright submillimeter galaxy (SMG), whereas the remaining three are faint SMGs newly uncovered by ALMA. If we exclude the two brightest sources, the contribution of the ALMA-detected faint SMGs to the infrared extragalactic background light is estimated to be ~ 4.1^{+5.4}_{-3.0} Jy deg^{-2}, which corresponds to ~ 16^{+22}_{-12}% of the infrared extragalactic background light. This suggests that their contribution to the infrared extragalactic background light is as large as that of bright SMGs. We identified multi-wavelength counterparts of the five ALMA sources. One of the sources (SXDF-ALMA3) is extremely faint in the optical to near-infrared region despite its infrared luminosity (L_IR ~ 1e12 L_sun or SFR ~ 100 M_sun yr^{-1}). By fitting the spectral energy distributions (SEDs) at the optical-to-near-infrared wavelengths of the remaining four ALMA sources, we obtained the photometric redshifts (z_photo) and stellar masses (M_*): z_photo ~ 1.3-2.5, M_* ~ (3.5-9.5)e10 M_sun. We also derived their star formation rates (SFRs) and specific SFRs (sSFRs) as ~ 30-200 M_sun yr^{-1} and ~ 0.8-2 Gyr^{-1}, respectively. These values imply that they are main-sequence star-forming galaxies.

ALMA Reveals Strong [C II] Emission in a Galaxy Embedded in a Giant Lyα Blob at z = 3.1

We report the result from observations conducted with the Atacama Large Millimeter/submillimeter Array (ALMA) to detect [C ii] 158 μm fine structure line emission from galaxies embedded in one of the most spectacular Lyα blobs (LABs) at z = 3.1, SSA22-LAB1. Of three dusty star-forming galaxies previously discovered by ALMA 860 μm dust continuum survey toward SSA22-LAB1, we detected the [C ii] line from one, LAB1-ALMA3 at z = 3.0993 ± 0.0004. No line emission was detected, associated with the other ALMA continuum sources or from three rest-frame UV/optical selected z_(spec) ≃ 3.1 galaxies within the field of view. For LAB1-ALMA3, we find relatively bright [C ii] emission compared to the infrared luminosity (L_([C ii])/L_(IR) ≈ 0.01) and an extremely high [C ii] 158 μm and [N ii] 205 μm emission line ratio (L_([C ii])/L_([N ii]) > 55). The relatively strong [C ii] emission may be caused by abundant photodissociation regions and sub-solar metallicity, or by shock heating. The origin of the unusually strong [C ii] emission could be causally related to the location within the giant LAB, although the relationship between extended Lyα emission and interstellar medium conditions of associated galaxies is yet to be understand.

SCUBA-2 Ultra Deep Imaging EAO Survey (STUDIES): Faint-end Counts at 450 μm

The SCUBA-2 Ultra Deep Imaging EAO Survey (STUDIES) is a three-year JCMT Large Program aiming to reach the 450 μm confusion limit in the COSMOS-CANDELS region to study a representative sample of the high-redshift far-infrared galaxy population that gives rise to the bulk of the far-infrared background. We present the first-year data from STUDIES. We reached a 450 μm noise level of 0.91 mJy for point sources at the map center, covered an area of 151 arcmin2, and detected 98 and 141 sources at 4.0σ and 3.5σ, respectively. Our derived counts are best constrained in the 3.5–25 mJy regime using directly detected sources. Below the detection limits, our fluctuation analysis further constrains the slope of the counts down to 1 mJy. The resulting counts at 1–25 mJy are consistent with a power law having a slope of −2.59 (±0.10 for 3.5–25 mJy, and

ALMA deep field in SSA22: Blindly detected CO emitters and [C II] emitter candidates

{}_{-0.7}^{+0.4}

The SXDF-ALMA 2 arcmin2 Deep Survey: stacking rest-frame near-infrared selected objects

for 1–3.5 mJy). There is no evidence of a faint-end termination or turnover of the counts in this flux density range. Our counts are also consistent with previous SCUBA-2 blank-field and lensing-cluster surveys. The integrated surface brightness from our counts down to 1 mJy is 90.0 ± 17.2 Jy deg−2, which can account for up to

SCUBA-2 Ultra Deep Imaging EAO Survey (STUDIES). II. Structural properties and near-infrared morphologies of faint submillimeter galaxies

{83}_{-16}^{+15} \%