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111 results on '"Carvalho, Matheus C."'

1. A multiwavelength overview of the giant spiral UGC 2885

Author

Carvalho, Matheus C., Naguleswaran, Bavithra, Barmby, Pauline, Gorski, Mark, Köenig, Sabine, Holwerda, Benne, and Young, Jason E.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

UGC 2885 (z = 0.01935) is one of the largest and most massive galaxies in the local Universe, yet its undisturbed spiral structure is unexpected for such an object and unpredicted in cosmological simulations. Understanding the detailed properties of extreme systems such as UGC 2885 can provide insight on the limits of scaling relations and physical processes driving galaxy evolution. Our goal is to understand whether UGC 2885 has followed a similar evolutionary path to other high-mass galaxies by examining its place on the fundamental metallicity relation and the star-forming main sequence. We present new observations of UGC 2885 with the CFHT and IRAM 30-m telescopes. These novel data are used to respectively calculate metallicity and molecular hydrogen mass values. We estimate stellar mass (M*) and star formation rate (SFR) based on mid-infrared observations with the Wide-field Infrared Survey Explorer. We find global metallicities Z = 9.28, 9.08 and 8.74 at the 25 kpc ellipsoid from N2O2, R23 and O3N2 indices, respectively. This puts UGC 2885 at the high end of the galaxy metallicity distribution. The molecular hydrogen mass is calculated as M(H2)=(1.89+/-0.24)e11 Msun, the SFR as 1.63+/-0.72 Msun/yr and the stellar mass as (4.83 +/- 1.52)e11 Msun, which gives a star formation efficiency (SFE = SFR/M(H2)) of (8.67+/-4.20)e12/yr. This indicates that UGC 2885 has an extremely high molecular gas content when compared to known samples of star forming galaxies (~100 times more) and a relatively low SFR for its current gas content. We conclude that UGC 2885 has gone through cycles of star formation periods, which increased its stellar mass and metallicity to its current state. The mechanisms that are fueling the current molecular gas reservoir and keeping the galaxy from producing stars remain uncertain. We discuss the possibility that a molecular bar is quenching star forming activity., Comment: A&A accepted; 15 pages, 14 figures

Published
2024

13. Adapting an elemental analyser to perform high‐temperature catalytic oxidation for dissolved organic carbon measurements in water.

Author

Carvalho, Matheus C.

Subjects
*DISSOLVED organic matter, *DISSOLVED oxygen in water, *PLATINUM catalysts, *STABLE isotopes, *SEAWATER salinity, *CARBON isotopes
Abstract

Rationale: Many laboratories employ elemental analyzers (EAs) coupled to isotope ratio mass spectrometers (IRMSs) to measure carbon stable isotope ratios (δ13C) in solid samples. Dissolved organic carbon (DOC) in most natural water samples cannot be analyzed using this approach unless time‐consuming preconcentration is employed. Methods: An EA‐IRMS can be used to measure DOC δ13C in natural waters without the need for sample preconcentration by employing high‐temperature catalytic oxidation. An autosampler injects water into the EA reactor at 680°C filled with platinum catalyst beads, where all carbon is converted to CO2. Remaining water and halides are removed, while CO2 is trapped in a cryotrap and later released to the IRMS. Results: Measurements were accurate (deviation <0.3‰ compared to solid sample measurements) and precise (error of 0.3‰ for concentrations ≥46 μM). Blanks were present and accounted for. Salinity up to seawater level did not affect accuracy or precision, but limited the number of samples that could be run before cleaning of the reactor was needed. DOC δ13C in a river/estuary varied between −25.7 and −23.2‰, with higher values for waters with higher salinity, as expected. Deep‐sea water reference material had a value of −22.9 ± 0.5‰, very similar to those found in recent reports employing similar techniques. Conclusion: Adapting an EA is a feasible approach for the measurement of DOC δ13C in natural waters. The low cost and simplicity of the system allow its use in any laboratory already equipped with EA‐IRMS. [ABSTRACT FROM AUTHOR]

Published
2023
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17. Technical note: Coupling infrared gas analysis and cavity ring down spectroscopy for autonomous, high-temporal-resolution measurements of DIC and δ13C–DIC

Author

Call, Mitchell, Schulz, Kai G., Carvalho, Matheus C., Santos, Isaac R., and Maher, Damien T.

Abstract

A new approach to autonomously determine concentrations of dissolved inorganic carbon (DIC) and its carbon stable isotope ratio (δ13C–DIC) at high temporal resolution is presented. The simple method requires no customised design. Instead it uses two commercially available instruments currently used in aquatic carbon research. An inorganic carbon analyser utilising non-dispersive infrared detection (NDIR) is coupled to a Cavity Ring-down Spectrometer (CRDS) to determine DIC and δ13C–DIC based on the liberated CO2 from acidified aliquots of water. Using a small sample volume of 2 mL, the precision and accuracy of the new method was comparable to standard isotope ratio mass spectrometry (IRMS) methods. The system achieved a sampling resolution of 16 min, with a DIC precision of ±1.5 to 2 µmol kg−1 and δ13C–DIC precision of ±0.14 ‰ for concentrations spanning 1000 to 3600 µmol kg−1. Accuracy of 0.1 ± 0.06 ‰ for δ13C–DIC based on DIC concentrations ranging from 2000 to 2230 µmol kg−1 was achieved during a laboratory-based algal bloom experiment. The high precision data that can be autonomously obtained by the system should enable complex carbonate system questions to be explored in aquatic sciences using high-temporal-resolution observations.

Published
2018

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