A Tolman Surface Brightness Test for Universal Expansion, and the Evolution of Elliptical Galaxies in Distant Clusters

We use the intercept of the elliptical galaxy radius--surface brightness (SB) relation at a fixed metric radius as the standard condition for the Tolman SB test of the universal expansion. We use surface photometry in the optical and near-IR of elliptical galaxies in Abell~2390 ($z=0.23$) and Abell~851 ($z=0.41$), and compare them to the Coma cluster at $z\approx 0$. The photometric data for each cluster are well-described by the Kormendy relation $r_e \propto \Sigma_e^{A}$, where $A=-0.9$ in the optical and $A=-1.0$ in the near-IR. The scatter about this near-IR relation is only $0.076$ in $\log r_e$ at the highest redshift, which is much smaller than at low redshifts, suggesting a remarkable homogeneity of the cluster elliptical population at $z=0.41$. We use the intercept of these fixed-slope correlations at $R_e = 1$~kpc (assuming $H_0=75$~km~s$^{-1}$~Mpc$^{-1}$, $\Omega_0=0.2$, and $\Lambda_0=0$, where the results are only weakly dependent on the cosmology) to construct the Tolman SB test for these three clusters. The data are fully consistent with universal expansion if we assume simple models of passive evolution for elliptical galaxies, but are inconsistent with a non-expanding geometry (the tired light cosmology) at the $5 \, \sigma$ confidence level at $z=0.41$. These results suggest luminosity evolution in the restframe $K$-band of $0.36 \pm 0.14$~mag from $z = 0.41$ to the present, and are consistent with the ellipticals having formed at high redshift. The SB intercept in elliptical galaxy correlations is thus a powerful tool for investigating models of their evolution for significant lookback times.Comment: to appear in The Astrophysical Journal (Letters); 13 pages, including 3 Postscript figures and 1 table; uuencoded, compressed format; the paper is also available in various formats from http://astro.caltech.edu/~map/map.bibliography.refereed.htm

Reliability analysis and repair activity for the components of 350 kw inverters in a large scale grid-connected photovoltaic system

The reliability of photovoltaic (PV) generators is strongly affected by the performance of Direct Current/Alternating Current (DC/AC) converters, being the major source of PV under-performance. However, generally, their reliability is not investigated at component level: thus, the present work presents a reliability analysis and the repair activity for the components of full bridge DC/AC converters. In the first part of the paper, a reliability analysis using failure rates from literature is carried out for 132 inverters (AC rated power of 350 kW each) with global AC power of 46 MW in a large scale grid-connected PV plant. Then, in the second part of the work, results from literature are compared with data obtained by analyzing industrial maintenance reports in the years 2015–2017. In conclusion, the yearly energy losses involved in the downtime are quantified, as well as their availability

B3 0003+387: AGN Marked Large-Scale Structure at z=1.47?

We present evidence for a significant overdensity of red galaxies, as much as a factor of 14 over comparable field samples, in the field of the z=1.47 radio galaxy B3 0003+387. The colors and luminosities of the brightest red galaxies are consistent with their being at z>0.8. The radio galaxy and one of the red galaxies are separated by 5" and show some evidence of a possible interaction. However, the red galaxies do not show any strong clustering around the radio galaxy nor around any of the brighter red galaxies. The data suggest that we are looking at a wall or sheet of galaxies, possibly associated with the radio galaxy at z=1.47. Spectroscopic redshifts of these red galaxies will be necessary to confirm this large-scale structure.Comment: 19 pages, 7 figures, LaTeX2e/AASTeX v5.0.2. The full photometric catalog is included as a separate deluxetable file. To appear in the Astronomical Journal (~Nov 00

Near-Infrared Adaptive Optics Imaging of the Central Regions of Nearby Sc Galaxies: I. M33

Near-infrared images obtained with the Canada-France-Hawaii Telescope (CFHT) Adaptive Optics Bonnette (AOB) are used to investigate the stellar content within 18 arcsec of the center of the Local Group spiral galaxy M33. AGB stars with near-infrared spectral-energy distributions similar to those of giants in the solar neighborhood and Baade's Window are detected over most of the field. The bolometric luminosity function (LF) of these stars has a discontinuity near M_{bol} = -5.25, and comparisons with evolutionary tracks suggest that most of the AGB stars formed in a burst of star formation 1 - 3 Gyr in the past. The images are also used to investigate the integrated near-infrared photometric properties of the nucleus and the central light concentration. The nucleus is bluer than the central light concentration, in agreement with previous studies at visible wavelengths. The CO index of the central light concentration 0.5 arcsec from the galaxy center is 0.05, which corresponds to [Fe/H] = -1.2 for simple stellar systems. Hence, the central light concentration could not have formed from the chemically-enriched material that dominates the present-day inner disk of M33.Comment: 23 pages of text + 11 figures; to appear in A

Uncovering Spiral Structure in Flocculent Galaxies

We present K'(2.1 micron) observations of four nearby flocculent spirals, which clearly show low-level spiral structure and suggest that kiloparsec-scale spiral structure is more prevalent in flocculent spirals than previously supposed. In particular, the prototypical flocculent spiral NGC 5055 is shown to have regular, two-arm spiral structure to a radius of 4 kpc in the near infrared, with an arm-interarm contrast of 1.3. The spiral structure in all four galaxies is weaker than that in grand design galaxies. Taken in unbarred galaxies with no large, nearby companions, these data are consistent with the modal theory of spiral density waves, which maintains that density waves are intrinsic to the disk. As an alternative, mechanisms for driving spiral structure with non-axisymmetric perturbers are also discussed. These observations highlight the importance of near infrared imaging for exploring the range of physical environments in which large-scale dynamical processes, such as density waves, are important.Comment: 12 pages AASTeX; 3 compressed PS figures can be retrieved from ftp://ftp.astro.umd.edu/pub/michele as file thornley.tar (1.6Mbytes). Accepted to Ap.J. Letters.(Figures now also available here, and from ftp://ftp.astro.umd.edu/pub/michele , in GIF format.

New application of superconductors: high sensitivity cryogenic light detectors

In this paper we describe the current status of the CALDER project, which is developing ultra-sensitive light detectors based on superconductors for cryogenic applications. When we apply an AC current to a superconductor, the Cooper pairs oscillate and acquire kinetic inductance, that can be measured by inserting the superconductor in a LC circuit with high merit factor. Interactions in the superconductor can break the Cooper pairs, causing sizable variations in the kinetic inductance and, thus, in the response of the LC circuit. The continuous monitoring of the amplitude and frequency modulation allows to reconstruct the incident energy with excellent sensitivity. This concept is at the basis of Kinetic Inductance Detectors (KIDs), that are characterized by natural aptitude to multiplexed read-out (several sensors can be tuned to different resonant frequencies and coupled to the same line), resolution of few eV, stable behavior over a wide temperature range, and ease in fabrication. We present the results obtained by the CALDER collaboration with 2x2 cm2 substrates sampled by 1 or 4 Aluminum KIDs. We show that the performances of the first prototypes are already competitive with those of other commonly used light detectors, and we discuss the strategies for a further improvement

Characterization of the KID-Based Light Detectors of CALDER

The aim of the Cryogenic wide-Area Light Detectors with Excellent Resolution (CALDER) project is the development of light detectors with active area of $5\times5$ cm$^2$ and noise energy resolution smaller than 20 eV RMS, implementing phonon-mediated kinetic inductance detectors. The detectors are developed to improve the background suppression in large-mass bolometric experiments such as CUORE, via the double read-out of the light and the heat released by particles interacting in the bolometers. In this work, we present the characterization of the first light detectors developed by CALDER. We describe the analysis tools to evaluate the resonator parameters (resonant frequency and quality factors) taking into account simultaneously all the resonance distortions introduced by the read-out chain (as the feed-line impedance and its mismatch) and by the power stored in the resonator itself. We detail the method for the selection of the optimal point for the detector operation (maximizing the signal-to-noise ratio). Finally, we present the response of the detector to optical pulses in the energy range of 0-30 keV

Low-Mass Star Formation and the Initial Mass Function in the Rho Ophiuchi Cloud Core

We have obtained moderate-resolution (R=800-1200) K-band spectra for ~100 stars within and surrounding the cloud core of rho Oph. We have measured spectral types and continuum veilings and have combined this information with results from new deep imaging. The IMF peaks at about 0.4 M_sun and slowly declines to the hydrogen burning limit with a slope of ~-0.5 in logarithmic units (Salpeter is +1.35). Our lower limits on the numbers of substellar objects demonstrate that the IMF probably does not fall more steeply below the hydrogen burning limit, at least down to ~0.02 M_sun. We then make the first comparison of mass functions of stars and pre-stellar clumps (Motte, Andre, & Neri) measured in the same region. The similar behavior of the two mass functions in rho Oph supports the suggestion of Motte et al. and Testi & Sargent that the stellar mass function in young clusters is a direct product of the process of cloud fragmentation. After considering the effect of extinction on the SED classifications of the sample, we find that ~17% of the rho Oph stars are Class I, implying ~0.1 Myr for the lifetime of this stage. In spectra separated by two years, we observe simultaneous variability in the Br gamma emission and K-band continuum veiling for two stars, where the hydrogen emission is brighter in the more heavily veiled data. This behavior indicates that the disk may contribute significantly to continuous K-band emission, in contrast to the proposal that the infalling envelope always dominates. Our detection of strong 2 micron veiling (r_K=1-4) in several Class II and III stars, which should have disks but little envelope material, further supports this proposition.Comment: 35 pages, 14 figures, accepted to Ap