PAHs and star formation in the HII regions of nearby galaxies M83 and M33

We present mid-infrared (MIR) spectra of HII regions within star-forming galaxies M83 and M33. Their emission features are compared with Galactic and extragalactic HII regions, HII-type galaxies, starburst galaxies, and Seyfert/LINER type galaxies. Our main results are as follows: (i) the M33 and M83 HII regions lie in between Seyfert/LINER galaxies and HII-type galaxies in the 7.7/11.3 - 6.2/11.3 plane, while the different sub-samples exhibiting different 7.7/6.2 ratios; (ii) Using the NASA Ames PAH IR Spectroscopic database, we demonstrate that the 6.2/7.7 ratio does not effectively track PAH size, but the 11.3/3.3 PAH ratio does; (iii) variations on the 17 $\mu$m PAH band depends on object type; however, there is no dependence on metallicity for both extragalactic HII regions and galaxies; (iv) the PAH/VSG intensity ratio decreases with the hardness of the radiation field and galactocentric radius (Rg), yet the ionization alone cannot account for the variation seen in all of our sources; (v) the relative strength of PAH features does not change significantly with increasing radiation hardness, as measured through the [NeIII]/[NeII] ratio and the ionization index; (vi) We present PAH SFR calibrations based on the tight correlation between the 6.2, 7.7, and 11.3 $\mu$m PAH luminosities with the 24 $\mu$m luminosity and the combination of the 24 $\mu$m and H$\alpha$ luminosity; (vii) Based on the total luminosity from PAH and FIR emission, we argue that extragalactic HII regions are more suitable templates in modeling and interpreting the large scale properties of galaxies compared to Galactic HII regions.Comment: 26 pages, 24 figures, 6 tables. Accepted for publication in MNRA

Polycyclic Aromatic Hydrocarbon Size Tracers

We examine the dependence of polycyclic aromatic hydrocarbon (PAH) band intensity ratios as a function of the average number of carbon atoms and assess their effectiveness as tracers for PAH size, utilising the data, models, and tools provided by the NASA Ames PAH Infrared Spectroscopic Database. To achieve this, we used spectra from mixtures of PAHs of different ionisation fractions, following a size distribution. Our work, congruent with earlier findings, shows that band ratios that include the 3.3 ${\mu}$m PAH band provide the best PAH size tracers for small-to-intermediate sized PAHs. In addition, we find that band ratios that include the sum of the 15-20 ${\mu}$m PAH features (I$_{\Sigma_{15-20}}$) and the 6.2 or 7.7 ${\mu}$m bands also serve as good tracers for PAH size in the case of small-to-intermediate sized PAHs, for objects under a similar PAH size distribution as with the presented models. For different PAH size distributions, the application of a scaling factor to the I$_{6.2}$/I$_{\Sigma_{15-20}}$ ratio can provide estimates for the size of the small-to-intermediate PAH population within sources. Employment of the I$_{6.2}$/I$_{\Sigma_{15-20}}$ and I$_{7.7}$/I$_{\Sigma_{15-20}}$ ratios can be of particular interest for JWST observations limited only to $\sim$ 5-28 ${\mu}$m MIRI(-MRS) coverage.Comment: 8 pages, 5 figures; Accepted for publication in MNRA

The Star Formation Reference Survey - III. A multiwavelength view of star formation in nearby galaxies

We present multiwavelength global star formation rate (SFR) estimates for 326 galaxies from the Star Formation Reference Survey in order to determine the mutual scatter and range of validity of different indicators. The widely used empirical SFR recipes based on 1.4 GHz continuum, 8.0 μm polycyclic aromatic hydrocarbons (PAHs), and a combination of far-infrared (FIR) plus ultraviolet (UV) emission are mutually consistent with scatter of ≲0.3 dex. The scatter is even smaller, ≲0.24 dex, in the intermediate luminosity range 9.3 \u3c log(L60 μm/L⊙) \u3c 10.7. The data prefer a non-linear relation between 1.4 GHz luminosity and other SFR measures. PAH luminosity underestimates SFR for galaxies with strong UV emission. A bolometric extinction correction to far-UV luminosity yields SFR within 0.2 dex of the total SFR estimate, but extinction corrections based on UV spectral slope or nuclear Balmer decrement give SFRs that may differ from the total SFR by up to 2 dex. However, for the minority of galaxies with UV luminosity \u3e 5 × 109 L⊙ or with implied far-UV extinction \u3c 1mag, the UV spectral slope gives extinction corrections with 0.22 dex uncertainty

On the interaction between the island divertor heat fluxes, the scrape-off layer radial electric field and the edge turbulence in Wendelstein 7-X plasmas

The formation of the radial electric field, E-r in the scrape-off layer (SOL) has been experimentally studied for attached divertor conditions in stellarator W7-X. The main objective of this study is to test the validity in a complex three-dimensional (3D) island divertor of simple models, typically developed in tokamaks, relating E-r in the SOL to the sheath potential drop gradient at the target. Additionally, we investigate the effect of the edge E-r shear on the reduction of density fluctuation amplitude, a well-established phenomenon according to the existing bibliography. The main diagnostic for measurements in the SOL is a V-band Doppler reflectometer that can provide the measurement of the E-r and density fluctuations with good spatial resolution. 3D measurements of divertor parameters have been carried out using infrared cameras, with the exponential decay length of the divertor heat flux (lambda(q)) resulting in a suitable proxy for the model-relevant lambda(T), the exponential decay length of the temperature at the divertor. In the investigated attached regimes, it is shown for the first time that the formation of the E-r in the SOL depends on parameters at the divertor, following a E-r proportional to T-e/lambda(q) qualitatively similar to that found in a tokamak. Then, from the analyzed plasmas, the observed E-r shear at the edge is linked to a moderate local reduction of the amplitude of density fluctuations

Comparison of the Impact of Ga-68-DOTATATE and F-18-FDG PET/CT on Clinical Management in Patients with Neuroendocrine Tumors

This study aimed to assess the clinical impact of 68Ga-DOTATATE and 18F-fluorodeoxyglucose with respect to the management plan and to evaluate the prognostic value of both tracers. Methods: A total of 104 patients (55 males, 49 females; median age 58 years, range 20–90) with histopathologically proven neuroendocrine tumors (NETs) underwent both 68Ga-DOTATATE and 18F-FDG PET/CT. Twenty-eight patients (26.9%) had poorly differentiated (PD) and 76 (73.1%), well-differentiated tumors. PET/CT results and SUVs were compared with prognostic factors such as pathologic grading (G1, G2, G3), chromogranin A, and proliferation index (Ki67). Results: 68Ga-DOTATATE and 18F-FDG PET/CT findings were discordant in 65 (62.5%) and concordant in 39 (37.5%) pts. PET/CT results changed the therapeutic plan in 84 (80.8%) pts. In 22 (21.1%) pts decision making was based on 18F-FDG findings, in 32 (30.8%) on findings with both radiotracers, and in 50 (48.1%) on 68Ga-DOTATATE findings. The most frequent management decision based on 18F-FDG was initiation of chemotherapy (10 pts, 47.6%). The most common treatment decision due to 68Ga-DOTATATE was initiation of peptide receptor radionuclide therapy (14 pts, 27.4%). In 11/28 (39.2%) pts with PD NETs the management decision was based only on 18F-FDG results. For 68Ga-DOTATATE, SUVmax was higher for G1 and lower for G3 tumors (p=0.012). However, no significant differences in 18F-FDG-derived SUVs were observed between different tumor grades (p=0.38). Mann-Whitney test showed significant differences in 68Ga-DOTATATE SUVmax between tumors with Ki<5% and tumors with Ki>5% (p=0.004), without significance differences in 18F-FDG SUVmax. Log-rank analysis showed statistically significant differences in survival for patients with bone vs soft tissue or no metastasis for both 18F-FDG (p=0.037) and 68Ga-DOTATATE (p=0.047). Overall survival was found to decline rapidly with increasing histological grade (p=0.001), with estimated survival of 91 months for G1, 59 months for G2, and 48 months for G3. Conclusion: 18F-FDG PET/CT had no clinical impact in G1 NETs and moderate impact in G2 NETs. However in PD NETs, 18F-FDG PET/CT plays a significant clinical role in combination with 68Ga-DOTATATE. 68Ga DOTATATE SUVmax values relate to tumor grade and Ki67 index and can be used prognostically

A far-ultraviolet-driven photoevaporation flow observed in a protoplanetary disk.

Most low-mass stars form in stellar clusters that also contain massive stars, which are sources of far-ultraviolet (FUV) radiation. Theoretical models predict that this FUV radiation produces photodissociation regions (PDRs) on the surfaces of protoplanetary disks around low-mass stars, which affects planet formation within the disks. We report James Webb Space Telescope and Atacama Large Millimeter Array observations of a FUV-irradiated protoplanetary disk in the Orion Nebula. Emission lines are detected from the PDR; modeling their kinematics and excitation allowed us to constrain the physical conditions within the gas. We quantified the mass-loss rate induced by the FUV irradiation and found that it is sufficient to remove gas from the disk in less than a million years. This is rapid enough to affect giant planet formation in the disk