We present AKARI 2.5–5 μm spectra of 145 local luminous infrared galaxies (LIRG; LIR ≥ 1011 L⊙) in the Great Observatories All-sky LIRG Survey (GOALS). In all of the spectra, we measure the line ...fluxes and equivalent widths (EQWs) of the polycyclic aromatic hydrocarbon (PAH) at 3.3 μm and the hydrogen recombination line Brα at 4.05 μm, with apertures matched to the slit sizes of the Spitzer low-resolution spectrograph and with an aperture covering ∼95% of the total flux in the AKARI two-dimensional (2D) spectra. The star formation rates (SFRs) derived from the Brα emission measured in the latter aperture agree well with SFRs estimated from LIR, when the dust extinction correction is adopted based on the 9.7 μm silicate absorption feature. Together with the Spitzer Infrared Spectrograph (IRS) 5.2–38 μm spectra, we are able to compare the emission of the PAH features detected at 3.3 μm and 6.2 μm. These are the two most commonly used near/mid-infrared indicators of starburst or active galactic nucleus (AGN) dominated galaxies. We find that the 3.3 μm and 6.2 μm PAH EQWs do not follow a linear correlation and at least a third of the galaxies classified as AGN-dominated sources using the 3.3 μm feature are classified as starbursts based on the 6.2 μm feature. These galaxies have a bluer continuum slope than galaxies that are indicated to be starburst-dominated by both PAH features. The bluer continuum emission suggests that their continuum is dominated by stellar emission rather than hot dust. We also find that the median Spitzer/IRS spectra of these sources are remarkably similar to the pure starburst-dominated sources indicated by high PAH EQWs in both 3.3 μm and 6.2 μm. Based on these results, we propose a revised starburst/AGN diagnostic diagram using 2–5 μm data: the 3.3 μm PAH EQW and the continuum color, Fν(4.3 μm)/Fν(2.8 μm). We use the AKARI and Spitzer spectra to examine the performance of our new starburst/AGN diagnostics and to estimate 3.3 μm PAH fluxes using the James Webb Space Telescope (JWST) photometric bands in the redshift range 0 < z < 5. Of the known PAH features and mid-infrared high ionization emission lines used as starburst/AGN indicators, only the 3.3 μm PAH feature is observable with JWST at z > 3.5, because the rest of the features at longer wavelengths fall outside the JWST wavelength coverage.
Although measuring the gas metallicity in galaxies at various redshifts is crucial to constrain galaxy evolutionary scenarios, only rest-frame optical emission lines have been generally used to ...measure the metallicity. This has prevented us to accurately measure the metallicity of dust-obscured galaxies, and accordingly to understand the chemical evolution of dusty populations, such as ultraluminous infrared galaxies. Here we propose diagnostics of the gas metallicity based on infrared fine-structure emission lines, which are nearly unaffected by dust extinction even the most obscured systems. Specifically, we focus on fine-structure lines arising mostly from Hii regions, not in photo-dissociation regions, to minimize the dependence and uncertainties of the metallicity diagnostics from various physical parameters. Based on photoionization models, we show that the emission-line flux ratio of (Oiii51.80+Oiii88.33)/Niii57.21 is an excellent tracer of the gas metallicity. The individual line ratios Oiii51.80/Niii57.21 or Oiii88.33/Niii57.21 can also be used as diagnostics of the metallicity, but they are more strongly dependent on the gas density. The line ratios Oiii88.33/Oiii51.80 and Nii121.7/Niii57.21 can be used to measure and, therefore, account for the dependences on the gas density and ionization parameter, respectively. We show that these diagnostic fine-structure lines are detectable with Herschel in luminous infrared galaxies out z ~ 0.4. Metallicity measurements with these fine-structure lines will be feasible at relatively high redshift (z ~ 1 or more) with SPICA, the future infrared space observatory.
We present the data and our analysis of mid-infrared atomic fine-structure emission lines detected in Spitzer/Infrared Spectrograph high-resolution spectra of 202 local Luminous Infrared Galaxies ...(LIRGs) observed as part of the Great Observatories All-sky LIRG Survey (GOALS). We compare ratios of the emission-line fluxes to those predicted from stellar photo-ionization and shock-ionization models to constrain the physical and chemical properties of the gas in the starburst LIRG nuclei. A significant fraction of the GOALS sources (80) have resolved neon emission-line profiles (FWHM > or =, slanted 600 km s super(-1)) and five show clear differences in the velocities of the NeIII or Nev emission lines, relative to NeII, of more than 200 km s super(-1).
Summary
Background
Processed foods are part of daily life. Almost all processed foods contain food additives such as sweeteners, preservatives and colourants. From childhood, it is difficult to avoid ...consuming food additives. It is thought that oral tolerance for food antigens is acquired during early life. If tolerance fails, adverse immune responses to food proteins may occur.
Objective
We hypothesized that food additives prevent acquisition of oral tolerance and aimed to verify the safety of food additives.
Methods
We induced experimental oral tolerance in mice for ovalbumin (OVA), a food antigen, by previous oral treatment with OVA before sensitization with OVA injections. Food additives were administered at the induction of oral tolerance, and food allergy was induced by repeated administration of OVA. Symptoms of food allergy were defined as a change in body temperature and allergic diarrhoea.
Results
Saccharin sodium and a mixture of food additives inhibited acquisition of oral tolerance. Hypothermia and allergic diarrhoea with elevation of OVA‐specific IgE were induced in the murine model of oral tolerance. Analyses of antigen‐presenting cells in mesenteric lymph nodes showed that food additives affected their manner of migration. Additionally, food additives decreased the proportion of CD25hi regulatory T cells among CD4+ T cells in the mesenteric lymph nodes.
Conclusions and Clinical Relevance
A large amount of food additives may prevent acquisition of oral tolerance. Intake of food additives in early life may increase the risk of food allergies.
In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) on the mid-infrared (MIR) luminosity and the redshift. We constructed 12 and 22 mum luminosity ...functions (LFs) at 0.006 < or =, slant z < or =, slant 0.3 using Wide-field Infrared Survey Explorer (WISE) data. Combining the WISE catalog with Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 223,982 galaxies at 12 mum and 25,721 galaxies at 22 mum for spectroscopic classification. We then identified 16,355 AGNs at 12 mum and 4683 AGNs at 22 mum by their optical emission lines and cataloged classifications in the SDSS. Following that, we estimated the CF as the fraction of Type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that the CF decreased with increasing MIR luminosity, regardless of the choice of Type 2 AGN classification criteria, and the CF did not change significantly with redshift for z < or =, slant 0.2. Furthermore, we carried out various tests to determine the influence of selection bias and confirmed that similar dependences exist, even when taking these uncertainties into account. The luminosity dependence of the CF can be explained by the receding torus model, but the "modified" receding torus model gives a slightly better fit, as suggested by Simpson.
We report new limits on the absolute brightness and spatial fluctuations of the cosmic infrared background (CIB) via the AKARI satellite. We carried out observations at 65, 90, 140, and 160 Delta *mm ...as a cosmological survey in AKARI Deep Field South, which is one of the lowest cirrus regions with a contiguous area of the sky. After removing bright galaxies and subtracting zodiacal and Galactic foregrounds from the measured sky brightness, we successfully measured the CIB brightness and its fluctuations across a wide range of angular scales, from arcminutes to degrees. The measured CIB brightness is consistent with previous results reported from COBE data, but significantly higher than the lower limits at 70 and 160 Delta *mm obtained via Spitzer from the stacking analysis of selected 24 Delta *mm sources. The discrepancy with the Spitzer result is possibly due to a new galaxy population at high redshift obscured by hot dust or unknown diffuse emission. From a power spectrum analysis at 90 Delta *mm, two components were identified: the CIB fluctuations with shot noise due to individual galaxies in a small angular scale from the beam size up to 10 arcminutes, and Galactic cirrus emission dominating at the largest angular scales of a few degrees. The overall shape of the power spectrum at 90 Delta *mm is very similar to that at longer wavelengths, as observed by Spitzer and the Balloon-borne Large-Aperture Submillimeter Telescope (BLAST). Our power spectrum, with an intermediate angular scale of 10-30 arcminutes, gives a firm upper limit for galaxy clustering, which was found by Spitzer and BLAST. Moreover, the color of the CIB fluctuations, which is obtained by combining our data with the previous results, is as red as ultra-luminous infrared galaxies at high redshift. These galaxies are not likely to provide the majority of the CIB emission at 90 Delta *mm, but are responsible for the fluctuations. Our results provide new constraints on the evolution and clustering properties of distant infrared galaxies and any diffuse emission from the early universe.
We report a search for fluctuations of the sky brightness toward the north ecliptic pole with the Japanese infrared astronomical satellite AKARI, at 2.4, 3.2, and 4.1 mu m. We obtained circular maps ...with 10' diameter fields of view, which clearly show a spatial structure on the scale of a few hundred arcseconds. A power spectrum analysis shows that there is a significant excess fluctuation at angular scales larger than 100'' that cannot be explained by zodiacal light, diffuse Galactic light, shot noise of faint galaxies, or clustering of low-redshift galaxies. These results are consistent with observations at 3.6 and 4.5 mu m by NASA's Spitzer Space Telescope. The fluctuating component observed at large angular scales has a blue stellar spectrum which is similar to that of the spectrum of the excess isotropic emission observed with the Infrared Telescope in Space. A significant spatial correlation between wavelength bands was found, and the slopes of the linear correlations are consistent with the spectrum of the excess fluctuation. These findings indicate that the detected fluctuation could be attributed to the first stars of the universe, i.e., Population III stars. The observed fluctuation provides an important constraint on the era of the first stars.
We study the behaviour of polycyclic aromatic hydrocarbon (PAH) emission in galaxies at z = 0.3–1.4 using 1868 samples from the revised catalogue of AKARI North Ecliptic Pole Deep survey. The ...continuous filter coverage at 2–24 μm makes it possible to measure 8 μm luminosity, which is dominated by PAH emission, for galaxies at up to z = 2. We compare the IR8 (≡LIR/L(8)) and 8 μm to 4.5 μm luminosity ratio (νL(8) /νL(4.5)) with the starburstiness, RSB, defined as excess of specific star-formation rate over that of main-sequence galaxy. All AGN candidates were excluded from our sample using a spectral energy distribution fitting. We find νL(8) /νL(4.5) increases with starburstiness at log RSB< 0.5 and stays constant at higher starburstiness. On the other hand, IR8 is constant at log RSB< 0, while it increases with starburstiness at log RSB> 0. This behaviour is seen in all redshift range of our study. These results indicate that starburst galaxies have deficient PAH emission compared with main-sequence galaxies. We also find that galaxies with extremely high νL(8) /νL(4.5) ratio have only moderate starburstiness. These results suggest that starburst galaxies have compact star-forming regions with intense radiation, which destroys PAHs, and/or have dusty HII regions resulting in a lack of ionising photons.
We present the first broadband Delta *l = 1 mm spectrum toward the z = 2.56 Cloverleaf quasar, obtained with Z-Spec, a grating spectrograph on the 10.4 m Caltech Submillimeter Observatory. The ...190-305 GHz observation band corresponds to the rest frame 272-444 Delta *mm, and we measure the dust continuum as well as all four transitions of carbon monoxide (CO) lying in this range. The power-law dust emission, F Delta *n = 14 mJy( Delta *n/240 GHz)3.9 is consistent with the published continuum measurements. The CO J = 6 -> 5, J = 8 -> 7, and J = 9 -> 8 measurements are the first, and now provide the highest-J CO information in this source. Our measured CO intensities are very close to the previously published interferometric measurements of J = 7 -> 6, and we use all available transitions and our 13CO upper limits to constrain the physical conditions in the Cloverleaf molecular gas disk. We find a large mass (2-50 X 109 M ) of highly excited gas with thermal pressure nT > 106 K cm-3. The ratio of the total CO cooling to the far-IR dust emission exceeds that in the local dusty galaxies, and we investigate the potential heating sources for this bulk of warm molecular gas. We conclude that both UV photons and X-rays likely contribute, and discuss implications for a top-heavy stellar initial mass function arising in the X-ray-irradiated starburst. Finally, we present tentative identifications of other species in the spectrum, including a possible detection of the H2O \20,2 -> 11,1 transition at Delta *lrest = 303 Delta *mm.
We present a photometric catalog for Spitzer Space Telescope warm mission observations of the North Ecliptic Pole (NEP; centered at R.A. = 18h00m00s, decl. = 66d33m38 552). The observations are ...conducted with IRAC in the 3.6 and 4.5 m bands over an area of 7.04 deg2, reaching 1 depths of 1.29 Jy and 0.79 Jy in the 3.6 m and 4.5 m bands, respectively. The photometric catalog contains 380,858 sources with 3.6 and 4.5 m band photometry over the full-depth NEP mosaic. Point-source completeness simulations show that the catalog is 80% complete down to 19.7 AB. The accompanying catalog can be used for constraining the physical properties of extragalactic objects, studying the AGN population, measuring the infrared colors of stellar objects, and studying the extragalactic infrared background light.
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