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

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.

Computing Matveev's complexity via crystallization theory: the orientable case

By means of a slight modification of the notion of GM-complexity introduced in [Casali, M.R., Topol. Its Appl., 144: 201-209, 2004], the present paper performs a graph-theoretical approach to the computation of (Matveev's) complexity for closed orientable 3-manifolds. In particular, the existing crystallization catalogue C-28 available in [Lins, S., Knots and Everything 5, World Scientific, Singapore, 1995] is used to obtain upper bounds for the complexity of closed orientable 3-manifolds triangulated by at most 28 tetrahedra. The experimental results actually coincide with the exact values of complexity, for all but three elements. Moreover, in the case of at most 26 tetrahedra, the exact value of the complexity is shown to be always directly computable via crystallization theory

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

Measurements and optimization of the light yield of a TeO2_2 crystal

Bolometers have proven to be good instruments to search for rare processes because of their excellent energy resolution and their extremely low intrinsic background. In this kind of detectors, the capability of discriminating alpha particles from electrons represents an important aspect for the background reduction. One possibility for obtaining such a discrimination is provided by the detection of the Cherenkov light which, at the low energies of the natural radioactivity, is only emitted by electrons. This paper describes the method developed to evaluate the amount of light produced by a crystal of TeO$_2$ when hit by a 511 keV photon. The experimental measurements and the results of a detailed simulation of the crystal and the readout system are shown and compared. A light yield of about 52 Cherenkov photons per deposited MeV was measured. The effect of wrapping the crystal with a PTFE layer, with the aim of maximizing the light collection, is also presented

A Contracting, Turbulent, Starless Core in the Serpens Cluster

We present combined single-dish and interferometric CS(2--1) and N2H+(1--0) observations of a compact core in the NW region of the Serpens molecular cloud. The core is starless according to observations from optical to millimeter wavelengths and its lines have turbulent widths and ``infall asymmetry''. Line profile modeling indicates supersonic inward motions v_in>0.34 km/s over an extended region L>12000AU. The high infall speed and large extent exceeds the predictions of most thermal ambipolar diffusion models and points to a more dynamical process for core formation. A short (dynamic) timescale, ~1e5 yr=L/v_in, is also suggested by the low N2H+ abundance ~1e-10.Comment: 11 pages including 2 figures. Accepted for publication in the Astrophysical Journal Letter

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

A closer look at the X-ray transient XTE J1908+094: identification of two new near-infrared candidate counterparts

We had reported in Chaty, Mignani, Israel (2002) on the near-infrared (NIR) identification of a possible counterpart to the black hole candidate XTE J1908+094 obtained with the ESO/NTT. Here, we present new, follow-up, CFHT adaptive optics observations of the XTE J1908+094 field, which resolved the previously proposed counterpart in two objects separated by about 0.8". Assuming that both objects are potential candidate counterparts, we derive that the binary system is a low-mass system with a companion star which could be either an intermediate/late type (A-K) main sequence star at a distance of 3-10 kpc, or a late-type ($>$K) main sequence star at a distance of 1-3 kpc. However, we show that the brighter of the two objects (J ~ 20.1, H ~ 18.7, K' ~ 17.8) is more likely to be the real counterpart of the X-ray source. Its position is more compatible with our astrometric solution, and colours and magnitudes of the other object are not consistent with the lower limit of 3 kpc derived independently from the peak bolometric flux of XTE J1908+094. Further multi-wavelength observations of both candidate counterparts are crucial in order to solve the pending identification.Comment: accepted for publication in MNRAS, 5 pages, 3 figure