Search

In this paper we present our imaging observations on the CO (7−6) line and its underlying continuum emission of the young submillimeter galaxy LESS 073 at redshift 4.755, using the Atacama Large Millimeter/submillimeter Array. At the achieved resolution of ∼ (8 × 6 kpc2), the CO (7−6) emission is largely unresolved (with a deconvolved size of ), and the continuum emission is totally unresolved. The CO (7−6) line emission has an integrated flux of 0.86 ± 0.08 Jy km s−1, and a line width of 343 ± 40 km s−1. The continuum emission has a flux density of 0.51 mJy. By fitting the observed far-infrared spectral energy distribution (SED) of LESS 073 with a single-temperature modified blackbody function, we obtained a dust temperature K, 60–100 μm flux density ratio , and total infrared luminosity . The SED-fit-based is consistent with those estimated from various line ratios as advocated by our earlier work, indicating that the proposed line-ratio-based method can be used to practically derive for high-z sources. The total molecular gas mass of LESS 073 is , and the inferred gas depletion time is about 43 Myr. [ABSTRACT FROM AUTHOR]

We present high-resolution (0.″17 × 0.″14) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the CO (6–5) line and 435 μm dust continuum emission within a ∼9″ × 9″ area centered on the nucleus of the galaxy NGC 5135. NGC 5135 is a well-studied luminous infrared galaxy that also harbors a Compton-thick active galactic nucleus (AGN). At the achieved resolution of 48 × 40 pc, the CO (6–5) and dust emissions are resolved into gas “clumps” along the symmetrical dust lanes associated with the inner stellar bar. The clumps have radii in the range of ∼45–180 pc and CO (6–5) line widths of ∼60–88 . The CO (6–5) to dust continuum flux ratios vary among the clumps and show an increasing trend with the [Fe ii]/Brγ ratios, which we interpret as evidence for supernova-driven shocked gas providing a significant contribution to the CO (6–5) emission. The central AGN is undetected in continuum, nor is it detected in CO (6–5) if its line velocity width is no less than ∼ 40 . We estimate that the AGN contributes at most 1% of the integrated CO (6–5) flux of 512 ± 24 Jy within the ALMA field of view, which in turn accounts for ∼32% of the CO (6–5) flux of the whole galaxy. [ABSTRACT FROM AUTHOR]

We present the results from our Atacama Large Millimeter/submillimeter Array (ALMA) imaging observations of the CO(7−6), [C i] 370 μm (hereafter [C i]), and [N ii] 205 μm (hereafter [N ii]) lines and their underlying continuum emission of BRI 1335-0417, an infrared bright quasar at z = 4.407. At the achieved resolutions of ∼1.″1 to 1.″2 (or 7.5–8.2 kpc), the continuum at 205 and 372 μm (rest frame), the CO(7−6), and the [C i] emissions are at best barely resolved whereas the [N ii] emission is well resolved with a beam-deconvolved major axis of 1.″3(±0.″3) or 9(±2) kpc. As a warm dense gas tracer, the CO(7−6) emission shows a more compact spatial distribution and a significantly higher peak velocity dispersion than the other two lines that probe lower density gas, a picture favoring a merger-triggered star formation (SF) scenario over an orderly rotating SF disk. The CO(7−6) data also indicate a possible QSO-driven gas outflow that reaches a maximum line-of-sight velocity of 500–600 km s−1. The far-infrared (FIR) dust temperature (Tdust ) of 41.5 K from a graybody fit to the continuum agrees well with the average Tdust inferred from various line luminosity ratios. The resulting LCO(7–6)/LFIR luminosity ratio is consistent with that of local luminous infrared galaxies powered predominantly by SF. The LCO(7–6)-inferred SF rate is 5.1(±1.5) × 103M⊙ yr−1. The system has an effective star-forming region of kpc in diameter and a molecular gas reservoir of ∼5 × 1011M⊙. [ABSTRACT FROM AUTHOR]

We present our high-resolution (0.″15 × 0.″13, ∼34 pc) observations of the CO (6−5) line emission, which probes the warm and dense molecular gas, and the 434 μm dust continuum emission in the nuclear region of the starburst galaxy IC 5179, conducted with the Atacama Large Millimeter Array (ALMA). The CO (6−5) emission is spatially distributed in filamentary structures with many dense cores and shows a velocity field that is characteristic of a circumnuclear rotating gas disk, with 90% of the rotation speed arising within a radius of ≲150 pc. At the scale of our spatial resolution, the CO (6−5) and dust emission peaks do not always coincide, with their surface brightness ratio varying by a factor of ∼10. This result suggests that their excitation mechanisms are likely different, as further evidenced by the southwest to northeast spatial gradient of both CO-to-dust continuum ratio and Pa-α equivalent width. Within the nuclear region (radius ∼ 300 pc) and with a resolution of ∼34 pc, the CO line flux (dust flux density) detected in our ALMA observations is 180 ± 18 Jy km s−1 (71 ± 7 mJy), which accounts for 22% (2.4%) of the total value measured by Herschel. [ABSTRACT FROM AUTHOR]

We present an analysis of dust properties of a sample of close major-merger galaxy pairs selected by Ks magnitude and redshift. The pairs represent the two populations of spiral–spiral (S+S) and mixed morphology spiral–elliptical (S+E). The Code Investigating GALaxy Emission software is used to fit dust models to the Two Micron All Sky Survey, Wide-Field Infrared Survey Explorer, and Herschel flux density measurements, and to derive the parameters describing the polycyclic aromatic hydrocarbons contribution, interstellar radiation field, and photodissociation regions. Model fits verify our previous Spitzer Space Telescope analysis that S+S and S+E pairs do not have the same level of enhancement of star formation and differ in dust composition. The spirals of mixed-morphology galaxy pairs do not exhibit the enhancements in interstellar radiation field and therefore dust temperature for spirals in S+S pairs in contrast to what would be expected according to standard models of gas redistribution due to encounter torques. This suggests the importance of the companion environment/morphology in determining the dust properties of a spiral galaxy in a close major-merger pair. [ABSTRACT FROM AUTHOR]

In this paper, we report our high-resolution (0.″20 × 0.″14 or ∼70 × 49 pc) observations of the CO(6-5) line emission, which probes warm and dense molecular gas, and the 434 μm dust continuum in the nuclear region of NGC 7130, obtained with the Atacama Large Millimeter Array (ALMA). The CO line and dust continuum fluxes detected in our ALMA observations are 1230 ± 74 Jy km s−1 and 814 ± 52 mJy, respectively, which account for 100% and 51% of their total fluxes. We find that the CO(6-5) and dust emissions are generally spatially correlated, but their brightest peaks show an offset of ∼70 pc, suggesting that the gas and dust emissions may start decoupling at this physical scale. The brightest peak of the CO(6-5) emission does not spatially correspond to the radio continuum peak, which is likely dominated by an active galactic nucleus (AGN). This, together with our additional quantitative analysis, suggests that the heating contribution of the AGN to the CO(6-5) emission in NGC 7130 is negligible. The CO(6-5) and the extinction-corrected Pa-α maps display striking differences, suggestive of either a breakdown of the correlation between warm dense gas and star formation at linear scales of <100 pc or a large uncertainty in our extinction correction to the observed Pa-α image. Over a larger scale of ∼2.1 kpc, the double-lobed structure found in the CO(6-5) emission agrees well with the dust lanes in the optical/near-infrared images. [ABSTRACT FROM AUTHOR]

In this paper, we present the measurements of the [N ii] 205 μm line for a flux-limited sample of 122 (ultra-)luminous infrared galaxies [(U)LIRGs] and 20 additional normal galaxies, obtained with the Herschel Space Observatory (Herschel). We explore the far-infrared (FIR) color dependence of the [N ii] 205 μm (L[N ii]205 μm) to the total infrared (LIR) luminosity ratio, and find that L[N ii]205 μm/LIR only depends modestly on the 70–160 μm flux density ratio () when , whereas such dependence becomes much steeper for . We also investigate the relation between L[N ii]205 μm and star formation rate (SFR), and show that L[N ii]205 μm has a nearly linear correlation with SFR, albeit the intercept of such a relation varies somewhat with , consistent with our previous conclusion that [N ii] 205 μm emission can serve as an SFR indicator with an accuracy of ∼0.4 dex, or ∼0.2 dex if is known independently. Furthermore, together with the Infrared Space Observatory measurements of [N ii], we use a total of ∼200 galaxies to derive the local [N ii] 205 μm luminosity function (LF) by tying it to the known IR LF with a bivariate method. As a practical application, we also compute the local SFR volume density () using the newly derived SFR calibrator and LF. The resulting yr−1 Mpc−3 agrees well with previous studies. Finally, we determine the electron densities (ne) of the ionized medium for a subsample of 12 (U)LIRGs with both [N ii] 205 μm and [N ii] 122 μm data, and find that ne is in the range of ∼1–100 cm−3, with a median value of 22 cm−3. [ABSTRACT FROM AUTHOR]