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We present an 8 pc × 5 pc resolution view of the central ∼200 pc region of the nearby starburst galaxy NGC 253, based on ALMA Band 7 ( or GHz) observations covering 11 GHz. We resolve the nuclear starburst of NGC 253 into eight dusty star-forming clumps, 10 pc in scale, for the first time. These clumps, each of which contains (4–10) of dust (assuming that the dust temperature is 25 K) and up to massive (O5V) stars, appear to be aligned in two parallel ridges, while they have been blended in previous studies. Despite the similarities in sizes and dust masses of these clumps, their line spectra vary drastically from clump to clump, although they are separated by only ∼10 pc. Specifically, one of the clumps, Clump 1, exhibits line-confusion-limited spectra with at least 36 emission lines from 19 molecules (including CH3OH, HNCO, H2CO, CH3CCH, H2CS, and H3O+) and a hydrogen recombination line (H26α), while far fewer kinds of molecular lines are detected in some other clumps where fragile species, such as complex organic molecules and HNCO, completely disappear from their spectra. We demonstrate the existence of hot molecular gas ( K) in the former clump, which suggests that the hot and chemically rich environments are localized within a 10-pc-scale star-forming clump. [ABSTRACT FROM AUTHOR]

We present our ALMA multi-transition molecular line observational results for the ultraluminous infrared galaxy IRAS 20551−4250, which is known to contain a luminous buried active galactic nucleus and shows detectable vibrationally excited (v2 = 1f) HCN and HNC emission lines. The rotational J = 1–0, 4–3, and 8–7 of HCN, , and HNC emission lines were clearly detected at a vibrational ground level (v = 0). Vibrationally excited (v2 = 1f) J = 4–3 emission lines were detected for HCN and HNC, but not for . Their observed flux ratios further support our previously obtained suggestion, based on J = 3–2 data, that (1) infrared radiative pumping plays a role in rotational excitation at v = 0, at least for HCN and HNC, and (2) HCN abundance is higher than and HNC. The flux measurements of the isotopologue H13CN, , and HN13C J = 3–2 emission lines support the higher HCN abundance scenario. Based on modeling with collisional excitation, we constrain the physical properties of these line-emitting molecular gases, but find that higher HNC rotational excitation than HCN and is difficult to explain, due to the higher effective critical density of HNC. We consider the effects of infrared radiative pumping using the available 5–30 μm infrared spectrum and find that our observational results are well-explained if the radiation source is located at 30–100 pc from the molecular gas. The simultaneously covered very bright CO J = 3–2 emission line displays a broad emission wing, which we interpret as being due to molecular outflow activity with the estimated rate of . [ABSTRACT FROM AUTHOR]

We present the results of a blind millimeter line emitter search using ALMA Band 6 data with a single-frequency tuning toward four gravitational lensing clusters (RXJ1347.5−1145, Abell S0592, MACS J0416.1−2403, and Abell 2744). We construct 3D signal-to-noise ratio (S/N) cubes with 60 and 100 MHz binning, and search for millimeter line emitters. We do not detect any line emitters with a peak S/N > 5, although we do find a line emitter candidate with a peak S/N ≃ 4.5. These results provide upper limits to the CO(3−2), CO(4−3), CO(5−4), and [C ii] luminosity functions at z ≃ 0.3, 0.7, 1.2, and 6, respectively. Because of the magnification effect of gravitational lensing clusters, the new data provide the first constraints on the CO and [C ii] luminosity functions at unprecedentedly low luminosity levels, i.e., down to ≲10−3 – 10−1 Mpc−3 dex−1 at K km s−1 pc2 and ≲10−3–10−2 Mpc−3 dex−1 at , respectively. Although the constraints to date are not yet stringent, we find that the evolution of the CO and [C ii] luminosity functions are broadly consistent with the predictions of semi-analytical models. This study demonstrates that the wide observations with a single-frequency tuning toward gravitational lensing clusters are promising for constraining the CO and [C ii] luminosity functions. [ABSTRACT FROM AUTHOR]

We investigate gas contents of star-forming galaxies associated with protocluster 4C23.56 at z = 2.49 by using the redshifted CO (3–2) and 1.1 mm dust continuum with the Atacama Large Millimeter/submillimeter Array. The observations unveil seven CO detections out of 22 targeted Hα emitters (HAEs) and four out of 19 in 1.1 mm dust continuum. They have high stellar mass ( M⊙) and exhibit a specific star-formation rate typical of main-sequence star-forming galaxies at . Different gas-mass estimators from CO (3–2) and 1.1 mm yield consistent values for simultaneous detections. The gas mass () and gas fraction () are comparable to those of field galaxies, with )) , where is the CO-to-H2 conversion factor and A(Z) is the additional correction factor for the metallicity dependence of , and from CO (3–2). Our measurements place a constraint on the cosmic gas density of high-z protoclusters, indicating that the protocluster is characterized by a gas density higher than that of the general fields by an order of magnitude. We found with the CO(3–2) detections. The five ALMA CO detections occur in the region of highest galaxy surface density, where the density positively correlates with global star-forming efficiency (SFE) and stellar mass. Such correlations possibly indicate a critical role of the environment on early galaxy evolution at high-z protoclusters, though future observations are necessary for confirmation. [ABSTRACT FROM AUTHOR]

We present the detailed characterization of two extremely red submillimeter galaxies (SMGs), ASXDF1100.053.1 and 231.1, with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Jansky Very Large Array. These SMGs were originally selected using AzTEC at 1100 μm, and are observed by Herschel to be faint at 100–500 μm. Their (sub)millimeter colors are as red as—or redder—than known z ≳ 5 SMGs; indeed, ASXDF1100.053.1 is redder than HFLS 3, which lies at z = 6.3. They are also faint and red in the near-/mid-infrared: ∼1 μJy at IRAC 4.5 μm and <0.2 μJy in the Ks filter. These SMGs are also faint in the radio waveband, where F6GHz = 4.5 μJy for ASXDF1100.053.1 and F1.4GHz = 28 μJy for ASXDF1100.231.1, suggestive of and for ASXDF1100.053.1 and 231.1, respectively. ASXDF1100.231.1 has a flux excess in the 3.6 μm filter, probably due to Hα emission at z = 4–5. Derived properties of ASXDF1100.053.1 for z = 5.5–7.5 and 231.1 for z = 3.5–5.5 are as follows: their infrared luminosities are [6.5 − 7.4] × 1012 and [4.2–4.5] × 1012L⊙; their stellar masses are [0.9–2] × 1011 and [0.4–3] × 1010M⊙; their circularized half-light radii in the ALMA maps are ∼1 and ≲0.2 kpc (∼2–3 kpc for 90% of the total flux). Last, their surface infrared luminosity densities, ΣIR, are ∼1 × 1012 and ≳1.5 × 1013L⊙ kpc−2, similar to values seen for local (U)LIRGs. These data suggest that ASXDF1100.053.1 and 231.1 are compact SMGs at z ≳ 4 and can plausibly evolve into z ≳ 3 compact quiescent galaxies. [ABSTRACT FROM AUTHOR]

We present a positive correlation between the mass of dense molecular gas () of ∼100 pc scale circumnuclear disks (CNDs) and the black hole mass accretion rate () in a total of 10 Seyfert galaxies, based on data compiled from the literature and an archive (median aperture θmed = 220 pc). A typical of CNDs is 107–8 , estimated from the luminosity of the dense gas tracer, the HCN(1–0) emission line. Because dense molecular gas is the site of star formation, this correlation is virtually equivalent to the one between the nuclear star-formation rate and revealed previously. Moreover, the correlation was tighter for CND-scale gas than for the gas on kiloparsec or larger scales. This indicates that CNDs likely play an important role in fueling black holes, whereas greater than kiloparesec scale gas does not. To demonstrate a possible approach for studying the CND-scale accretion process with the Atacama Large Millimeter/submillimeter Array, we used a mass accretion model where angular momentum loss due to supernova explosions is vital. Based on the model prediction, we suggest that only the partial fraction of the mass accreted from the CND () is consumed as . However, agrees well with the total nuclear mass flow rate (i.e., + outflow rate). Although these results are still tentative with large uncertainties, they support the view that star formation in CNDs can drive mass accretion onto supermassive black holes in Seyfert galaxies. [ABSTRACT FROM AUTHOR]

We present the results of ALMA Cycle 2 observations of the ultraluminous infrared galaxy IRAS 20551−4250 at HCN/HCO+/HNC J = 3–2 lines at both vibrational ground (v = 0) and vibrationally excited (v2 = 1) levels. This galaxy contains a luminous buried active galactic nucleus (AGN), in addition to starburst activity, and our ALMA Cycle 0 data revealed a tentatively detected vibrationally excited HCN v2 = 1f J = 4–3 emission line. In our ALMA Cycle 2 data, the HCN/HCO+/HNC J = 3–2 emission lines at v = 0 are clearly detected. The HCN and HNC v2 = 1f J = 3–2 emission lines are also detected, but the HCO+v2 = 1f J = 3–2 emission line is not. Given the high energy level of v2 = 1 and the resulting difficulty of collisional excitation, we compared these results with those of the calculation of infrared radiative pumping, using the available infrared 5–35 μm spectrum. We found that all of the observational results were reproduced if the HCN abundance was significantly higher than that of HCO+ and HNC. The flux ratio and excitation temperature between v2 = 1f and v = 0, after correction for possible line opacity, suggests that infrared radiative pumping affects rotational (J-level) excitation at v = 0 at least for HCN and HNC. The HCN-to-HCO+v = 0 flux ratio is higher than those of starburst-dominated regions, and will increase even more when the derived high HCN opacity is corrected. The enhanced HCN-to-HCO+ flux ratio in this AGN-hosting galaxy can be explained by the high HCN-to-HCO+ abundance ratio and sufficient HCN excitation at up to J = 4, rather than the significantly higher efficiency of infrared radiative pumping for HCN than HCO+. [ABSTRACT FROM AUTHOR]

Compiling data from literature and the Atacama Large Millimeter/submillimeter Array archive, we show enhanced HCN(4–3)/HCO+(4–3) and/or HCN(4–3)/CS(7–6) integrated intensity ratios in circumnuclear molecular gas around active galactic nuclei (AGNs) compared to those in starburst (SB) galaxies (submillimeter HCN enhancement). The number of sample galaxies is significantly increased from our previous work. We expect that this feature could potentially be an extinction-free energy diagnostic tool of nuclear regions of galaxies. Non-LTE radiative transfer modelings of the above molecular emission lines involving both collisional and radiative excitation, as well as a photon trapping effect, were conducted to investigate the cause of the high line ratios in AGNs. As a result, we found that enhanced abundance ratios of HCN to HCO+ and HCN to CS in AGNs as compared to SB galaxies by a factor of a few to even ≳10 are a plausible explanation for the submillimeter HCN enhancement. However, a counterargument of a systematically higher gas density in AGNs than in SB galaxies can also be a plausible scenario. Although we cannot fully distinguish these two scenarios at this moment owing to an insufficient amount of multi-transition, multi-species data, the former scenario is indicative of abnormal chemical composition in AGNs. Regarding the actual mechanism to realize the composition, we suggest that it is difficult with conventional gas-phase X-ray-dominated region ionization models to reproduce the observed high line ratios. We might have to take into account other mechanisms such as neutral–neutral reactions that are efficiently activated in high-temperature environments and/or mechanically heated regions to further understand the high line ratios in AGNs. [ABSTRACT FROM AUTHOR]

We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 1 observations of the central kiloparsec region of the luminous type 1 Seyfert galaxy NGC 7469 with unprecedented high resolution (0.″5 ×0.″4 = 165 × 132 pc) at submillimeter wavelengths. Utilizing the wide bandwidth of ALMA, we simultaneously obtained HCN(4–3), HCO+(4–3), CS(7–6), and partially CO(3–2) line maps, as well as the 860 μm continuum. The region consists of the central ∼1″ component and the surrounding starburst ring with a radius of ∼1.″5–2.″5. Several structures connect these components. Except for CO(3–2), these dense gas tracers are significantly concentrated toward the central ∼1″, suggesting their suitability to probe the nuclear regions of galaxies. Their spatial distribution resembles well those of centimeter and mid-infrared continuum emissions, but it is anticorrelated with the optical one, indicating the existence of dust-obscured star formation. The integrated intensity ratios of HCN(4–3)/HCO+(4–3) and HCN(4–3)/CS(7–6) are higher at the active galactic nucleus (AGN) position than at the starburst ring, which is consistent with our previous findings (submillimeter-HCN enhancement). However, the HCN(4–3)/HCO+(4–3) ratio at the AGN position of NGC 7469 (1.11 ± 0.06) is almost half of the corresponding value of the low-luminosity type 1 Seyfert galaxy NGC 1097 (2.0 ± 0.2), despite the more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the ratio is comparable to that of the close vicinity of the AGN of NGC 1068 (∼1.5). Based on these results, we speculate that some heating mechanisms other than X-ray (e.g., mechanical heating due to an AGN jet) can contribute significantly for shaping the chemical composition in NGC 1097. [ABSTRACT FROM AUTHOR]

We report the source size distribution, as measured by ALMA millimetric continuum imaging, of a sample of 13 AzTEC-selected submillimeter galaxies (SMGs) at –6. Their infrared luminosities and star formation rates (SFRs) are 2– and ∼200–600 yr−1, respectively. The sizes of these SMGs range from 0.″10 to 0.″38, with a median of 0.″20 (FWHM), corresponding to a median circularized effective radius () of kpc, comparable to the typical size of the stellar component measured in compact quiescent galaxies at (cQGs)— kpc. The median surface SFR density of our SMGs is yr−1 kpc−2, comparable to that seen in local merger-driven (U)LIRGs rather than in extended disk galaxies at low and high redshifts. The discovery of compact starbursts in SMGs strongly supports a massive galaxy formation scenario wherein –6 SMGs evolve into the compact stellar components of cQGs. These cQGs are then thought to evolve into the most massive ellipticals in the local universe, mostly via dry mergers. Our results thus suggest that SMGs are the likely progenitors of massive local ellipticals, via cQGs, meaning that we can now trace the evolutionary path of the most massive galaxies over a period encompassing ∼90% of the age of the universe. [ABSTRACT FROM AUTHOR]

Recombinant viruses possessing reporter proteins have been generated for virus research. In the case of the family Flaviviridae, we recently generated recombinant viruses, including the hepatitis C virus of the genus Hepacivirus, Japanese encephalitis virus (JEV) of the genus Flavivirus, and bovine viral diarrhea virus of the genus Pestivirus; all three viruses possess an 11-amino-acid subunit derived from NanoLuc luciferase (HiBiT). Here, we further developed the recombinant viruses and investigated their utility in vivo. Recombinant viruses harboring HiBiT in the E, NS1, or NS3 protein constructed based on the predicted secondary structure, solventaccessible surface area, and root mean square fluctuation of the proteins exhibited comparable replication to that of the wild-type virus in vitro. The recombinant JEV carrying HiBiT in the NS1 protein exhibited propagation in mice comparable to that of the parental virus, and propagation of the recombinant was monitored by the luciferase activity. In addition, the recombinants of classical swine fever virus (CSFV) possessing HiBiT in the Erns or E2 protein also showed propagation comparable to that of the wild-type virus. The recombinant CSFV carrying HiBiT in Erns exhibited similar replication to the parental CSFV in pigs, and detection of viral propagation of this recombinant by luciferase activity was higher than that by quantitative PCR (qPCR). Taken together, these results demonstrated that the reporter Flaviviridae viruses generated herein are powerful tools for elucidating the viral life cycle and pathogeneses and provide a robust platform for the development of novel antivirals. [ABSTRACT FROM AUTHOR]