Infrared astronomy research and high altitude observations

Highlights are presented of studies of the emission mechanisms in the 4 to 8 micron region of the spectrum using a circular variable filter wheel spectrometer with a PbSnTe photovoltaic detector. Investigations covered include the spectroscopy of planets, stellar atmospheres, highly obscured objects in molecular clouds, planetary nebulae, H2 regions, and extragalactic objects

Mid-Infrared Galaxy Morphology Along the Hubble Sequence

The mid-infrared emission from 18 nearby galaxies imaged with the IRAC instrument on Spitzer Space Telescope samples the spatial distributions of the reddening-free stellar photospheric emission and the warm dust in the ISM. These two components provide a new framework for galaxy morphological classification, in which the presence of spiral arms and their emission strength relative to the starlight can be measured directly and with high contrast. Four mid-infrared classification methods are explored, three of which are based on quantitative global parameters (colors, bulge-to-disk ratio) similar to those used in the past for optical studies; in this limited sample, all correlate well with traditional B-band classification. We suggest reasons why infrared classification may be superior to optical classification.Comment: ApJS (in press), Spitzer Space Telescope Special Issue; 13 pages, LaTeX (or Latex, etc); Figure 1ab is large, color plate; full-resolution plates in .pdf format available at http://cfa-www.harvard.edu/irac/publications

Contribution of the Accretion Disk, Hot Corona, and Obscuring Torus to the Luminosity of Seyfert Galaxies: Integral and Spitzer Observations

We estimate the relative contributions of the supermassive black hole (SMBH) accretion disk, corona, and obscuring torus to the bolometric luminosity of Seyfert galaxies, using Spitzer mid-infrared (MIR) observations of a complete sample of 68 nearby active galactic nuclei (AGNs) from the INTEGRAL all-sky hard X-ray (HX) survey. This is the first HX-selected (above 15 keV) sample of AGNs with complementary high angular resolution, high signal-to-noise, MIR data. Correcting for the host galaxy contribution, we find a correlation between HX and MIR luminosities: L 15 μm∝L0.74 ± 0.06 HX. Assuming that the observed MIR emission is radiation from an accretion disk reprocessed in a surrounding dusty torus that subtends a solid angle decreasing with increasing luminosity (as inferred from the declining fraction of obscured AGNs), the intrinsic disk luminosity, L Disk, is approximately proportional to the luminosity of the corona in the 2-300 keV energy band, L Corona, with the L Disk/L Corona ratio varying by a factor of 2.1 around a mean value of 1.6. This ratio is a factor of ~2 smaller than for typical quasars producing the cosmic X-ray background. Therefore, over three orders of magnitude in luminosity, HX radiation carries a large, and roughly comparable, fraction of the bolometric output of AGNs. We estimate the cumulative bolometric luminosity density of local AGNs at ~(1-3) × 1040 erg s–1 Mpc–3. Finally, the Compton temperature ranges between kT c ≈ 2 and ≈6 keV for nearby AGNs, compared to kT c ≈ 2 keV for typical quasars, confirming that radiative heating of interstellar gas can play an important role in regulating SMBH growth

Coherent electronic and nuclear dynamics in a rhodamine heterodimer-DNA supramolecular complex

Elucidating the role of quantum coherences in energy migration within biological and artificial multichromophoric antenna systems is the subject of an intense debate. It is also a practical matter because of the decisive implications for understanding the biological processes and engineering artificial materials for solar energy harvesting. A supramolecular rhodamine heterodimer on a DNA scaffold was suitably engineered to mimic the basic donor-acceptor unit of light-harvesting antennas. Ultrafast 2D electronic spectroscopic measurements allowed identifying clear features attributable to a coherent superposition of dimer electronic and vibrational states contributing to the coherent electronic charge beating between the donor and the acceptor. The frequency of electronic charge beating is found to be 970 cm-1 (34 fs) and can be observed for 150 fs. Through the support of high level ab initio TD-DFT computations of the entire dimer, we established that the vibrational modes preferentially optically accessed do not drive subsequent coupling between the electronic states on the 600 fs of the experiment. It was thereby possible to characterize the time scales of the early time femtosecond dynamics of the electronic coherence built by the optical excitation in a large rigid supramolecular system at a room temperature in solution. © 2017 the Owner Societies.Multi valued and parallel molecular logi

Abundances in galactic H2 regions, 3: G25.4-0.2, G45.5+0.06, M8, S159 and DR22

Measurements of the ARII (6.99 microns), ArIII (8.99 microns), NeII (12.81 microns), SIII (18.71 microns), and SIV (10.51 microns) lines are presented for five compact HII regions along with continuum spectroscopy. From these data and radio data, lower limits to the elemental abundances of Ar, S, and Ne were deduced. The complex G25.4-0.2 is only 5.5 kpc from the galactic center, and is considerably overabundant in all these elements. Complex G45.5+0.06 is at seven kpc from the galactic center, and appears to be approximately consistent with solar abundance. The complex S159 in the Perseus Arm, at 12 kpc from the galactic center, has solar abundance, while M8 in the solar neighborhood may be somewhat overabundant in Ar and Ne. Complex DR 22, at 10 kpc from the galactic center in the Cygnus Arm, is overabundant in Ar. A summary of results from a series of papers on abundances is given

Stabilization of Ultracold Molecules Using Optimal Control Theory

In recent experiments on ultracold matter, molecules have been produced from ultracold atoms by photoassociation, Feshbach resonances, and three-body recombination. The created molecules are translationally cold, but vibrationally highly excited. This will eventually lead them to be lost from the trap due to collisions. We propose shaped laser pulses to transfer these highly excited molecules to their ground vibrational level. Optimal control theory is employed to find the light field that will carry out this task with minimum intensity. We present results for the sodium dimer. The final target can be reached to within 99% if the initial guess field is physically motivated. We find that the optimal fields contain the transition frequencies required by a good Franck-Condon pumping scheme. The analysis is able to identify the ranges of intensity and pulse duration which are able to achieve this task before other competing process take place. Such a scheme could produce stable ultracold molecular samples or even stable molecular Bose-Einstein condensates