scholarly journals Infrared Images of Merging Galaxies

1990 ◽  
Vol 124 ◽  
pp. 321-326
Author(s):  
G. S. Wright ◽  
P. A. James ◽  
R. D. Joseph ◽  
I. S. McLean ◽  
R. Doyon
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Interacting Galaxies ◽  
Infrared Images ◽  
Merging Galaxies ◽  
Giant Stars ◽  
Stellar Component ◽  
Infrared Wavelengths ◽  
Red Giant ◽  
Star Formation Regions

Infrared imaging of interacting galaxies is especially interesting because their optical appearance is often so chaotic due to extinction by dust and emission from star formation regions, that it is impossible to locate the nuclei or determine the true stellar distribution. However, at near-infrared wavelengths extinction is considerably reduced, and most of the flux from galaxies originates from red giant stars that comprise the dominant stellar component by mass. Thus near infrared images offer the opportunity to study directly components of galactic structure which are otherwise inaccessible. Such images may ultimately provide the framework in which to understand the activity taking place in many of the mergers with high IRAS luminosities.

scholarly journals Continuing the MODIS Dark Target Aerosol Time Series with VIIRS

2020 ◽  
Vol 12 (2) ◽  
pp. 308 ◽  
Author(s):  
Virginia Sawyer ◽  
Robert C. Levy ◽  
Shana Mattoo ◽  
Geoff Cureton ◽  
Yingxi Shi ◽  
...  
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Retrieval Algorithm ◽  
Spatial And Temporal Variability ◽  
Imaging Spectrometer ◽  
Standard Data ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Infrared Wavelengths ◽  
Good Agreement

For reflected sunlight observed from space at visible and near-infrared wavelengths, particles suspended in Earth’s atmosphere provide contrast with vegetation or dark water at the surface. This is the physical motivation for the Dark Target (DT) aerosol retrieval algorithm developed for the Moderate Resolution Imaging Spectrometer (MODIS). To extend the data record of aerosol optical depth (AOD) beyond the expected 20-year lifespan of the MODIS sensors, DT must be adapted for other sensors. A version of the DT AOD retrieval for the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi-National Polar-Orbiting Partnership (SNPP) is now mature enough to be released as a standard data product, and includes some upgraded features from the MODIS version. Differences between MODIS Aqua and VIIRS SNPP lead to some inevitable disagreement between their respective AOD measurements, but the offset between the VIIRS SNPP and MODIS Aqua records is smaller than the offset between those of MODIS Aqua and MODIS Terra. The VIIRS SNPP retrieval shows good agreement with ground-based measurements. For most purposes, DT for VIIRS SNPP is consistent enough and in close enough agreement with MODIS to continue the record of satellite AOD. The reasons for the offset from MODIS Aqua, and its spatial and temporal variability, are investigated in this study.

scholarly journals Optical & Near Infrared Imaging of NGC1275

1989 ◽  
Vol 134 ◽  
pp. 376-378
Author(s):  
D. H. Hughes ◽  
E. I. Robson ◽  
M. J. Ward
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Wavelength Region ◽  
Seyfert Galaxy ◽  
Elliptical Galaxies ◽  
Infrared Images ◽  
Different Populations ◽  
Reduced Data ◽  
Array Camera ◽  
Selection Of

We are currently studying a selection of active galaxies using the new IR array camera IRCAM on UKIRT. Our aim is to seperate the underlying stellar emission from that of the active galactic nucleus. Although the optical is the best wavelength region to discriminate between the different populations in the underlying spiral and elliptical galaxies, it is in the infrared that the contrast between the non-thermal central core and the surrounding galaxy is increased. We present reduced data from infrared images taken at 1.25, 1.65 and 2.2 μm with an image scale of 0.6 arcsec/pixel together with optical 0.44 and 0.55 μm CCD images of the Seyfert galaxy NGC1275.

scholarly journals Van der Waals two-color infrared photodetector

2022 ◽  
Vol 11 (1) ◽  
Author(s):  
Peisong Wu ◽  
Lei Ye ◽  
Lei Tong ◽  
Peng Wang ◽  
Yang Wang ◽  
...  
Keyword(s):  
Information Acquisition ◽  
Near Infrared ◽  
Multispectral Imaging ◽  
Infrared Imaging ◽  
Absolute Temperature ◽  
Cryogenic Cooling ◽  
Infrared Photodetector ◽  
Temperature Detection ◽  
Infrared Wavelengths ◽  
Increasing Demand

AbstractWith the increasing demand for multispectral information acquisition, infrared multispectral imaging technology that is inexpensive and can be miniaturized and integrated into other devices has received extensive attention. However, the widespread usage of such photodetectors is still limited by the high cost of epitaxial semiconductors and complex cryogenic cooling systems. Here, we demonstrate a noncooled two-color infrared photodetector that can provide temporal-spatial coexisting spectral blackbody detection at both near-infrared and mid-infrared wavelengths. This photodetector consists of vertically stacked back-to-back diode structures. The two-color signals can be effectively separated to achieve ultralow crosstalk of ~0.05% by controlling the built-in electric field depending on the intermediate layer, which acts as an electron-collecting layer and hole-blocking barrier. The impressive performance of the two-color photodetector is verified by the specific detectivity (D*) of 6.4 × 109 cm Hz1/2 W−1 at 3.5 μm and room temperature, as well as the promising NIR/MWIR two-color infrared imaging and absolute temperature detection.

Ammonia and Near-Infrared Observations of Southern Dark Clouds

1993 ◽  
Vol 10 (3) ◽  
pp. 236-240 ◽  
Author(s):  
T.L. Bourke ◽  
A.R. Hyland ◽  
G. Robinson ◽  
S.D. James
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Imaging System ◽  
Ammonia Emission ◽  
Infrared Images ◽  
Infrared Source ◽  
Visual Appearance ◽  
Infrared Observations ◽  
Dark Clouds ◽  
Ammonia Source

AbstractThe Parkes radio telescope has been used to search a list of small, dense southern dark clouds and Bok globules for ammonia emission at 23.7 GHz. The ammonia observations, together with IRAS data and the cloud’s visual appearance, have been used to determine a short list of dark clouds for observation with the infrared imaging system (IRIS) on the Anglo-Australian Telescope, in an attempt to determine the dust density distribution within the clouds. Near-infrared images of a number of the short listed clouds have been obtained with IRIS at J, H and K’. Preliminary results are reported for this ammonia survey, together with IRIS images of the strong ammonia source DC 297.7–2.8. Coincident with the dense ammonia core of this object is an IRAS ‘core’ source, IRAS 11590–6452 and an extremely interesting near-infrared source, which lies on the edge of the error ellipse of the IRAS source.

Near-infrared imaging of interacting galaxies

1990 ◽  
Vol 359 ◽  
pp. 72 ◽  
Author(s):  
Howard A. Bushouse ◽  
Michael W. Werner
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Interacting Galaxies ◽  
Near Infrared Imaging

scholarly journals Panchromatic calibration of Ca II triplet luminosity dependence

2020 ◽  
Vol 642 ◽  
pp. A197
Author(s):  
B. Dias ◽  
M. C. Parisi
Keyword(s):  
Near Infrared ◽  
Line Strength ◽  
Infrared Camera ◽  
Zero Point ◽  
Relative Magnitude ◽  
Magellanic Clouds ◽  
Giant Stars ◽  
Empirical Procedure ◽  
Red Giant Stars ◽  
Red Giant

Context. The line strength of the near-infrared Ca II triplet (CaT) lines are a proxy for measuring metallicity from integrated and individual stellar spectra of bright red giant stars. In the latter case it is a mandatory step to remove the magnitude (proxy for gravity, temperature, and luminosity) dependence from the equivalent width (EW) of the lines before converting them into metallicities. For decades the working empirical procedure has been to use the relative magnitude with respect to the horizontal branch level or red clump, with the advantage that it is independent from distance and extinction. Aims. The V filter is broadly adopted as the reference magnitude, although a few works have used different filters (I and Ks, for example). In this work we investigate the dependence of the CaT calibration using the griz filters from the Dark Energy Camera (DECam) and the Gemini Multi-Object Spectrograph (GMOS), the G filter from Gaia, the BVI filters from the Magellanic Clouds photometric survey (MCPS), and the YJKs filters from the Visible and Infrared Survey Telescope for Astronomy (VISTA) InfraRed CAMera (VIRCAM). We use as a reference the FOcal Reducer and low dispersion Spectrograph 2 (FORS2) V filter used in the original analysis of the sample. Methods. Red giant stars from clusters with known metallicity and available CaT EWs were used as reference. Public photometric catalogues were taken from the Survey of the MAgellanic Stellar History (SMASH) second data release, VISTA survey of the Magellanic Clouds system (VMC), Gaia, MCPS surveys, plus VIsible Soar photometry of star Clusters in tApi’i and Coxi HuguA (VISCACHA) GMOS data, for a selection of Small Magellanic Cloud clusters. The slopes were fitted using two and three lines to be applicable to most of the metallicity scales. Results. The magnitude dependence of the CaT EWs is well described by a linear relation using any filter analysed in this work. The slope increases with wavelength of the filters. The zero point (i.e. reduced EW), which is the metallicity indicator, remains the same. Conclusions. If the same line profile function is used with the same bandpasses and continuum regions, and the total EW comes from the same number of lines (2 or 3), then the reduced EW is the same regardless the filter used. Therefore, any filter can be used to convert the CaT equivalent widths into metallicity for a given CaT calibration.

scholarly journals Effective Temperature Scales of Red Giant Stars

1999 ◽  
Vol 191 ◽  
pp. 84-90
Author(s):  
David R. Alexander ◽  
Jason W. Ferguson ◽  
Robert F. Wing ◽  
Hollis R. Johnson ◽  
Peter H. Hauschildt ◽  
...  
Keyword(s):  
Effective Temperature ◽  
Near Infrared ◽  
Narrow Band ◽  
State Of The Art ◽  
Band System ◽  
Spectral Synthesis ◽  
Giant Stars ◽  
Red Giant ◽  
Absorption Features ◽  
The Continuum

We have completed a grid of spherically symmetric AGB star atmospheres using the state of the art spectral synthesis code PHOENIX. Models are constructed for stars with masses of 1 M⊙and 1.5 M⊙, spanning the range 10 to 3300 L⊙in luminosity and 2500 to 5200 K in effective temperature. We find that grains of Al2O3and CaTiO3among other species form in atmospheres cooler than Teff= 3000 K. In the coolest models the grains cause a weakening of the TiO absorption features in the red and near infrared of up to 30% through both a depression of the continuum and a depletion of the TiO number abundance. We use spectrophotometric observations from a number of catalogs to determine effective temperature – spectral class and effective temperature – color relationships. We also compare synthetic colors calculated from our models with observations of M giants on Wing's 8-color narrow-band system of classification photometry.

scholarly journals Observational properties of a general relativistic instability supernova from a primordial supermassive star

2021 ◽  
Vol 503 (1) ◽  
pp. 1206-1213
Author(s):  
Takashi J Moriya ◽  
Ke-Jung Chen ◽  
Kimihiko Nakajima ◽  
Nozomu Tominaga ◽  
Sergei I Blinnikov
Keyword(s):  
Black Holes ◽  
Near Infrared ◽  
Infrared Imaging ◽  
High Redshift ◽  
Plateau Phase ◽  
Infrared Images ◽  
High Redshift Galaxies ◽  
James Webb Space Telescope ◽  
General Relativistic ◽  
The Time Domain

ABSTRACT We present the expected observational properties of a general relativistic instability supernova (GRSN) from the 55 500 M⊙ primordial (Population III) star. Supermassive stars exceeding $10^4\, \mathrm{M}_\odot$ may exist in the early Universe. They are generally considered to collapse through the general relativistic instability to be seed black holes to form supermassive ($\sim 10^9\, \mathrm{M}_\odot$) black holes observed as high-redshift quasars. Some of them, however, may explode as GRSNe if the explosive helium burning unbinds the supermassive stars following the collapse triggered by the general relativistic instability. We perform the radiation hydrodynamics simulation of the GRSN starting shortly before the shock breakout. We find that the GRSN is characterized by a long-lasting (550 d) luminous ($1.5\times 10^{44}\, \mathrm{erg\, s^{-1}}$) plateau phase with the photospheric temperature of around 5000 K in the rest frame. The plateau phase lasts for decades when it appears at high redshifts and it will likely be observed as a persistent source in the future deep near-infrared imaging surveys. Especially, the near-infrared images reaching 29 AB magnitude that can be obtained by Galaxy and Reionization EXplorer (G-REX) and James Webb Space Telescope (JWST) allow us to identify GRSNe up to z ≃ 15. Deeper images enable us to discover GRSNe at even higher redshifts. Having extremely red colour, they can be distinguished from other persistent sources such as high-redshift galaxies by using colour information. We conclude that the deep near-infrared images are able to constrain the existence of GRSNe from the primordial supermassive stars in the Universe even without the time domain information.

scholarly journals Kinematic and metallicity properties of the Aquarius dwarf galaxy from FORS2 MXU spectroscopy

2020 ◽  
Vol 634 ◽  
pp. A10 ◽  
Author(s):  
L. Hermosa Muñoz ◽  
S. Taibi ◽  
G. Battaglia ◽  
G. Iorio ◽  
M. Rejkuba ◽  
...  
Keyword(s):  
Near Infrared ◽  
Velocity Dispersion ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Major Axis ◽  
Stellar Feedback ◽  
Stellar Component ◽  
Red Giant ◽  
Gas Loss ◽  
The Individual

Context. Dwarf galaxies found in isolation in the Local Group (LG) are unlikely to have interacted with the large LG spirals, and therefore environmental effects such as tidal and ram-pressure stripping should not be the main drivers of their evolution. Aims. We provide insight into the internal mechanisms shaping LG dwarf galaxies by increasing our knowledge of the internal properties of isolated systems. Here we focus on the evolved stellar component of the Aquarius dwarf galaxy, whose kinematic and metallicity properties have only recently started to be explored. Methods. Spectroscopic data in the region of the near-infrared Ca II triplet lines has been obtained with FORS2 at the Very Large Telescope for 53 red giant branch (RGB) stars. These data are used to derive line-of-sight (l.o.s.) velocities and [Fe/H] of the individual RGB stars. Results. We derive a systemic velocity of −142.2+1.8−1.8 km s−1, in agreement with previous determinations from both the HI gas and stars. The internal kinematics of Aquarius appears to be best modelled by a combination of random motions (l.o.s. velocity dispersion of 10.3+1.6−1.3 km s−1) and linear rotation (with a gradient −5.0+1.6−1.9 km s−1 arcmin−1) along a PA = 139+17−27 deg, broadly consistent with the optical projected major axis. This rotation signal is significantly misaligned or even counter-rotating to that derived from the HI gas. We also find the tentative presence of a mild negative metallicity gradient and indications that the metal-rich stars have a colder velocity dispersion than the metal-poor ones. Conclusions. This work represents a significant improvement with respect to previous measurements of the RGB stars of Aquarius as it doubles the number of member stars already studied in the literature. We speculate that the misaligned rotation between the HI gas and evolved stellar component might have been the result of recent accretion of HI gas, or re-accretion after gas-loss due to internal stellar feedback.

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