Discovery of a Protocluster Core Associated with an Enormous Lya Nebula at z = 2.3

The MAMMOTH-1 nebula at z = 2.317 is an enormous Lyα nebula (ELAN) extending to a ∼440 kpc scale at the center of the extreme galaxy overdensity BOSS 1441. In this paper, we present observations of the CO(3 − 2) and 250 GHz dust-continuum emission from MAMMOTH-1 using the IRAM NOrthern Extended Millimeter Array. Our observations show that CO(3 − 2) emission in this ELAN has not extended widespread emission into the circum- and inter-galactic media. We also find a remarkable concentration of six massive galaxies in CO(3 − 2) emission in the central ∼100 kpc region of the ELAN. Their velocity dispersions suggest a total halo mass of M 200c ∼ 1013.1 M ⊙, marking a possible protocluster core associated with the ELAN. The peak position of the CO(3 − 2) line emission from the obscured AGN is consistent with the location of the intensity peak of MAMMOTH-1 in the rest-frame UV band. Its luminosity line ratio between the CO(3 − 2) and CO(1 − 0)r 3,1 is 0.61 ± 0.17. The other five galaxies have CO(3 − 2) luminosities in the range of (2.1–7.1) × 109 K km s−1 pc2, with the star-formation rates derived from the 250 GHz continuum of (<36)–224 M ⊙ yr−1. Follow-up spectroscopic observations will further confirm more member galaxies and improve the accuracy of the halo mass estimation.

Anomalous Hydrogen Recombination Line Ratios in Ultraluminous Infrared Galaxies

We conducted systematic observations of the H i Brα (4.05 μm) and Brβ (2.63 μm) lines in 52 nearby (z < 0.3) ultraluminous infrared galaxies (ULIRGs) with AKARI. Among 33 ULIRGs wherein the lines are detected, 3 galaxies show anomalous Brβ/Brα line ratios (∼1.0), which are significantly higher than those for case B (0.565). Our observations also show that ULIRGs have a tendency to exhibit higher Brβ/Brα line ratios than those observed in Galactic H ii regions. The high Brβ/Brα line ratios cannot be explained by a combination of dust extinction and case B since dust extinction reduces the ratio. We explore possible causes for the high Brβ/Brα line ratios and show that the observed ratios can be explained by a combination of an optically thick Brα line and an optically thin Brβ line. We simulated the H ii regions in ULIRGs with the Cloudy code, and our results show that the high Brβ/Brα line ratios can be explained by high-density conditions, wherein the Brα line becomes optically thick. To achieve a column density large enough to make the Brα line optically thick within a single H ii region, the gas density must be as high as n ∼ 108 cm−3. We therefore propose an ensemble of H ii regions, in each of which the Brα line is optically thick, to explain the high Brβ/Brα line ratio.

Edge-Based Licence-Plate Template Matching for Identifying Similar Vehicles

This paper presents licence-plate recognition for identifying vehicles with similar licence-plates. The method uses a modified licence-plate recognition pipeline, with licence-plate template matching replacing character segmentation and recognition. Only edge detection is used, combined with a method for calculating line ratio to locate and extract licence-plates. The extracted licence-plate templates are then compared for licence-plate matching. The results show that the method performs well in differing circumstances, and that it is computationally cost-effective. Results also show that licence-plate template matching is a reliable method of identifying similar vehicles, and has a lower computational cost when compared with character segmentation and recognition.

Assessing the sources of reionisation: a spectroscopic case study of a 30× lensed galaxy at z ∼ 5 with Lyα, C iv, Mg ii, and [Ne iii]

We present a detailed spectroscopic analysis of a galaxy at z ≃ 4.88 that is, by chance, magnified ∼30 × by gravitational lensing. Only three sources at z ≳ 5 are known with such high magnification. This particular source has been shown to exhibit widespread, high equivalent width ${\rm C\, {\small IV}}\, \lambda \, 1549$ emission, implying it is a unique example of a metal-poor galaxy with a hard radiation field, likely representing the galaxy population responsible for cosmic reionisation. Using UV nebular line ratio diagnostics, VLT/X-shooter observations rule out strong AGN activity, indicating a stellar origin of the hard radiation field instead. We present a new detection of ${[\rm Ne\, {\small III}]}\, \lambda \, 3870$ and use the [Ne iii]/[O ii] line ratio to constrain the ionisation parameter and gas-phase metallicity. Closely related to the commonly used [O iii]/[O ii] ratio, our [Ne iii]/[O ii] measurement shows this source is similar to local “Green Pea” galaxies and Lyman-continuum leakers. It furthermore suggests this galaxy is more metal poor than expected from the Fundamental Metallicity Relation, possibly as a consequence of excess gas accretion diluting the metallicity. Finally, we present the highest redshift detection of ${\rm Mg\, {\small II}}\, \lambda \, 2796$, observed at high equivalent width in emission, in contrast to more evolved systems predominantly exhibiting Mg ii absorption. Strong Mg ii emission has been observed in most z ∼ 0 Lyman-continuum leakers known and has recently been proposed as an indirect tracer of escaping ionising radiation. In conclusion, this strongly lensed galaxy, observed just 300 Myr after reionisation ends, enables testing of observational diagnostics proposed to constrain the physical properties of distant galaxies in the JWST/ELT era.

Spectroscopic evaluation of vibrational temperature and electron density in reduced pressure radio frequency nitrogen plasma

The optical emission spectroscopy technique is used to determine the vibrational temperature of the second positive band system,$$ N_{2} (C,\upsilon^{^{\prime}} - B,\upsilon^{^{\prime\prime}}$$ N 2 ( C , υ ′ - B , υ ″ ) in the wavelength range 367.1–380.5 nm by using the line-ratio and Boltzmann plot methods. The electron temperature is evaluated from the intensity ratio of the selected molecular bands corresponding to $$N_{2}^{ + } (B,\upsilon - X, \upsilon^{^{\prime}} , $$ N 2 + ( B , υ - X , υ ′ , 391.44 nm), and, $$N_{2} (C,\upsilon^{^{\prime}} - B,\upsilon^{^{\prime\prime}}$$ N 2 ( C , υ ′ - B , υ ″ , 375.4 nm) transitions, respectively. The selected bands have a different threshold of excitation energies and thus serve as a sensitive indicator of the electron energy distribution function (EEDF). The electron density has been determined from the intensity ratio of the molecular transitions corresponding to $$N_{2}^{ + } (B,\upsilon - X, \upsilon^{^{\prime}} , $$ N 2 + ( B , υ - X , υ ′ , 391.44 nm), and, $$ N_{2} (C,\upsilon^{^{\prime}} - B,\upsilon^{^{\prime\prime}}$$ N 2 ( C , υ ′ - B , υ ″ , 380.5 nm) for different levels of pressure and radio frequency power. The results show that the vibrational temperature decreases with increasing nitrogen fill pressure and radio frequency power. However, the electron temperature increases with radio frequency power and reduces with fill pressure. The electron density increases both with nitrogen fill pressure and radio frequency power that attributes to the effective collisional transfer of energy producing electron impact ionization. Plasma parameters show a significant dependence on discharge conditions and can be fine-tuned for specific surface treatments. Article Highlights Spectrum analysis of RF-driven nitrogen plasma for varying discharge conditions Evaluation of vibrational temperature using line-ratio and Boltzmann plot methods Comparison of vibrational temperatures for line-ratio and Boltzmann plot methods Evaluation of electron temperature and density using the intensity-ratio of bands Correlation of temperature and density with varying fill pressure and RF power

Gauging the effect of Supermassive Black Holes feedback on Quasar host galaxies

In order to gauge the role that active galactic nuclei (AGN) play in the evolution of galaxies via the effect of kinetic feedback in nearby QSO 2’s (z ∼ 0.3), we observed eight such objects with bolometric luminosities $L_{bol} \sim 10^{46}\rm {erg\, s^{-1}}$ using Gemini GMOS-IFU’s. The emission lines were fitted with at least two Gaussian curves, the broadest of which we attributed to gas kinetically disturbed by an outflow. We found that the maximum extent of the outflow ranges from ∼1 to 8 kpc, being ∼ 0.5 ± 0.3 times the extent of the [O iii] ionized gas region. Our ‘default’ assumptions for the gas density (obtained from the [S ii] doublet) and outflow velocities resulted in peak mass outflow rates of $\dot{M}_{out}^{{\tt def}}\sim$ 3 – 30 $\rm {M_{\odot }}\, yr^{-1}$ and outflow power of $\dot{E}_{out}^{{\tt def}}\sim \, 10^{41}$ – 1043 erg s−1. The corresponding kinetic coupling efficiencies are $\varepsilon _f^{{\tt def}}=\dot{E}_{out}^{{\tt def}}/L_{bol}\, \sim 7\times 10^{-4}$ – 0.5 %, with the average efficiency being only 0.06 % (0.01 % median), implying little feedback powers from ionized gas outflows in the host galaxies. We investigated the effects of varying assumptions and calculations on $\dot{M}_{out}$ and $\dot{E}_{out}$ regarding the ionized gas densities, velocities, masses and inclinations of the outflow relative to the plane of the sky, resulting in average uncertainties of one dex. In particular, we found that better indicators of the [O iii] emitting gas density than the default [S ii] line ratio, such as the [Ar iv]λλ4711,40 line ratio, result in almost an order of magnitude decrease in the ϵf.

Dense gas in local galaxies revealed by multiple tracers

We present 3 mm and 2 mm band simultaneously spectroscopic observations of HCN 1-0, HCO+ 1-0, HNC 1-0, and CS 3-2 with the IRAM 30 meter telescope, toward a sample of 70 sources as nearby galaxies with infrared luminosities ranging from several 105L⊙ to more than 1012L⊙. After combining HCN 1-0, HCO+ 1-0 and HNC 1-0 data from literature with our detections, relations between luminosities of dense gas tracers (HCN 1-0, HCO+ 1-0 and HNC 1-0) and infrared luminosities are derived, with tight linear correlations for all tracers. Luminosities of CS 3-2 with only our observations also show tight linear correlation with infrared luminosities. No systematic difference is found for tracing dense molecular gas among these tracers. Star formation efficiencies for dense gas with different tracers also do not show any trend along different infrared luminosities. Our study also shows that HCN/HCO+ line ratio might not be a good indicator to diagnose obscured AGN in galaxies.

Multiple HC3N line observations towards 19 Galactic massive star-forming regions

We performed observations of the HC3N (24–23, 17–16, 11–10, 8–7) lines towards a sample consisting of 19 Galactic massive star-forming regions with the Arizona Radio Observatory 12 m and Caltech Submillimeter Observatory 10.4 m telescopes. HC3N (24–23, 17–16, 11–10, 8–7) lines were detected in sources except for W 44, where only HC3N (17–16, 11–10) were detected. Twelve of the nineteen sources showed probable line wing features. The excitation temperatures were estimated from the line ratio of HC3N (24–23) to HC3N (17–16) for 18 sources and are in the range 23– 57 K. The line widths of higher-J transitions are larger than lower-J ones for most sources. This indicates that the inner dense warm regions have more violent turbulence or other motions (such as rotation) than outer regions in these sources. A possible cutoff tendency was found around LIR ∼ 106 L⊙ in the relation between LIR and full width at half maximum line widths.

Application of Y–ZrO2 microtubes as dielectric barrier material in a He atmospheric pressure micro-plasma jet

This work focused on the application of novel 8% yttria-stabilized Zr2O3 (YSZ) microtubes with an inner diameter of 60 µm as dielectric material in an atmospheric pressure micro-plasma jet (APPJ). Furthermore, a comparison with quartz microtubes allowed to study the effect of tube material on plasma properties. Optical emission spectroscopy was employed to determine various spectral line ratios including ratios of He lines 667 nm (31D-21P) to 728 nm (31S-21P) which is indicative of electric field strength. The 667/728 nm line ratio in the YSZ microtube was about 2/3 the value in the 60-µm quartz tube. However, increasing the quartz tube’s inner diameter from 60 to 500 µm decreased the 667/728 nm line ratio 40 times. Additionally, the spatio-temporal evolution of the ionization wave was measured in the YSZ microtube and the velocity of the ionization wave was determined to accelerate from 67 km/s near the powered electrode to 161 km/s near the tube orifice.