Stellar metals shine toward our eyes only Taking a different look at a familiar star may still yield surprises. Boggs et al. trained the x-ray vision of the NuSTAR observatory on the well-studied supernova 1987A. Core-collapse explosions such as SN 1987A produce a titanium isotope, 44 Ti, whose radioactive decay yields hard x-ray emission lines. All the emission associated with 44Ti appears to be from material moving toward us, with none moving away. This implies that the explosion was not symmetric. These findings help to explain the mechanics of SN 1987A and of core-collapse supernovae in general. Science , this issue p. 670

Radioactive decay

10.1126/science.aaa2259

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Mid-IR Spectroscopy of High-z SMGs: First Results

Astronomical Society of the Pacific eBooks (2007)

Karín Menéndez‐Delmestre A. W. Blain D. M. Alexander Ian Smail L. Armus

We present mid-infrared spectra of 5 submmillimeter galaxies at redshifts z = 0.65 − 2.38 taken with the Infrared Spectrograph aboard the Spitzer Space Telescope. Four of these sources have strong PAH features and the strength of these features are consistent with these galaxies being dominated by star formation. The other source displays a Mrk 231-type broad emission feature at restframe ~8 μm that does not conform to the typical 7.7/8.6 μm PAH complex in starburst galaxies, suggesting a more substantial AGN contribution.

Spitzer Space Telescope

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Fundamental differences in the properties of red and blue quasars: measuring the reddening and accretion properties with X-shooter

Monthly Notices of the Royal Astronomical Society (2022)

V. A. Fawcett D. M. Alexander D. J. Rosario Lizelke Klindt Elisabeta Lusso

ABSTRACT We have recently found fundamental differences in the radio properties of red quasars when compared to typical blue quasars. In this paper, we use data from the X-shooter spectrograph on the Very Large Telescope, providing spectral coverage from ∼3000–$25\,000\,$ Å, of a sample of 40 red and blue luminous quasars at 1.45 < z < 1.65 to explore the connections between the radio, emission-line, and accretion-disc properties. We fit various dust-extinction curves to the data and find that dust reddening can fully explain the observed colours for the majority of the red quasars in our sample, with moderate extinctions ranging from AV ∼ 0.06–0.7 mag. We confront our spectra with a simple thin accretion-disc model and find this can describe the continua of both the blue and red quasars, once corrected for dust extinction; we also find no significant differences in the accretion properties. We detect ionized outflows in a number of red and blue quasars, but do not find any significant evidence that they are more prevalent in the red quasar population. Overall our findings imply that the radio emission is more closely connected to circumnuclear/ISM opacity rather than accretion disc or outflow differences.

Extinction (optical mineralogy)

Opacity

OVV quasar

Outflow

10.1093/mnras/stac945

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EOR Development Screening of a Heterogeneous Heavy Oil Field - Challenges and Solutions

Jonathan Strauss D. M. Alexander Nasser Al Azri Mohammed Al-Habsi Talal Al-Musallami

10.2523/129157-ms

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Visible and short-wave infrared fiber-based snapshot imaging spectrometer with a custom high-throughput relay system

Optics Continuum (2023)

Jiawei Lu Desheng Zheng Razvan-Ionut Stoian Christopher Flynn D. M. Alexander

This paper presents the design and fabrication of a fiber-based snapshot imaging spectrometer working in both visible (490 nm-732 nm) and short-wave infrared (1090 nm - 1310 nm) ranges. To maximize the light collection efficiency, a custom relay system with 0.25 NA and 20 mm field of view (FOV) was designed and integrated. The bench setup showed that the custom relay system could fully resolve 10 µm fiber cores over the entire FOV among visible and short-wave infrared ranges. The numerical aperture (NA) match provided a 2.07X fold throughout improvement in the visible range and about 10X fold in the SWIR range compared to the previous generations, enabling imaging with a fast frame rate and under low illumination conditions. The presented imaging spectrometer generated spectral datacubes with 35000 spatial samplings and 23 spectral channels. Spectral urban imaging results obtained by the spectrometer in both visible and SWIR ranges are presented. Finally, we collected spectral images of apple bruising to show potential applications in the food quality industry.

Imaging spectrometer

Snapshot (computer storage)

Coded aperture

Frame rate

Spectral resolution

Field of view

10.1364/optcon.484551

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Tracking Down the Source Population Responsible for the Unresolved Cosmic 6-8 keV Background

American Astronomical Society Meeting Abstracts #220 (2012)

Yongquan Xue S. X. Wang W. N. Brandt Bin Luo D. M. Alexander

Tracking (education)

Background radiation

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The heats of solution of rare gases in water

D. M. Alexander

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Valoración de la agudeza visual en pacientes operados con facoemulsificación - Clinica Global Laser. 2016

Universidad Nacional Federico Villarreal (2018)

Coronel Valiente D. M. Alexander

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Environments of Luminous Low-frequency Radio Galaxies Since Cosmic Noon: Jet-mode Feedback Dominates in Groups

The Astrophysical Journal (2024)

Grayson C. Petter Ryan C. Hickox L. K. Morabito D. M. Alexander

Abstract Coupling between relativistic jets launched by accreting supermassive black holes and the surrounding gaseous media is a vital ingredient in galaxy evolution models. To constrain the environments in which this feedback takes place over cosmic time, we study the host-halo properties of luminous low-frequency radio galaxies ( L 150 MHz ≳ 10 25.25 W Hz −1 ) selected with the International Low-Frequency Array Telescope out to z ∼ 2 through tomographic clustering and cosmic microwave background lensing measurements. We find that these systems occupy halos characteristic of galaxy groups ( M h = 10 13 –10 14 h −1 M ⊙ ), evolving at a rate consistent with the mean growth rate of halos over the past ∼10 Gyr. The coevolution of the clustering and the luminosity function reveals that the duty cycle of these systems is of order ∼10% but has been mildly increasing since z ∼ 2, while the duty cycle of quasars has been declining. We estimate the characteristic kinetic heating power injected by powerful jets per halo as a function of mass, and compare to the same quantity injected by quasar winds. We find that powerful jet heating dominates over quasar winds in halos M h ≳ 10 13 h −1 M ⊙ at z < 2. These results conform to the paradigm of galaxy evolution in which mechanical jet power feedback is the dominant heating mechanism of the gas content of groups and clusters.

Noon

Mode (computer interface)

10.3847/1538-4357/ad6849

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High molecular gas content and star formation rates in local galaxies that host quasars, outflows, and jets

Monthly Notices of the Royal Astronomical Society (2020)

M. Jarvis C. M. Harrison V. Mainieri G. Calistro Rivera Prashin Jethwa

ABSTRACT We use a sample of powerful $z\, \approx \, 0.1$ type 2 quasars (‘obscured’; log [LAGN/erg s$^{-1}]\, \gtrsim \, 45$), which host kpc-scale ionized outflows and jets, to identify possible signatures of AGN feedback on the total molecular gas reservoirs of their host galaxies. Specifically, we present Atacama Pathfinder EXperiment (APEX) observations of the CO(2–1) transition for nine sources and the CO(6–5) for a subset of three. We find that the majority of our sample reside in starburst galaxies (average specific star formation rates – sSFR – of 1.7 Gyr−1), with the seven CO-detected quasars also having large molecular gas reservoirs (average Mgas = 1.3 × 1010 M⊙), even though we had no pre-selection on the star formation or molecular gas properties. Despite the presence of quasars and outflows, we find that the molecular gas fractions (Mgas/M⋆ = 0.1–1.2) and depletion times (Mgas/SFR = 0.16–0.95 Gyr) are consistent with those expected for the overall galaxy population with matched stellar masses and sSFRs. Furthermore, for at least two of the three targets with the required measurements, the CO(6–5)/CO(2–1) emission-line ratios are consistent with star formation dominating the CO excitation over this range of transitions. The targets in our study represent a gas-rich phase of galaxy evolution with simultaneously high levels of star formation and nuclear activity; furthermore, the jets and outflows do not have an immediate appreciable impact on the global molecular gas reservoirs.

10.1093/mnras/staa2196

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Citations (55)