Blue Tail Research Articles

The evolution of brightest cluster galaxies in the nearby Universe – I. Colours and stellar masses from the Sloan Digital Sky Survey and Wide Infrared Survey Explorer

We present a study of the evolution of brightest cluster galaxies (BCGs) in a sample of clusters at $0.05 \leq z<0.35$ from the SDSS and WISE with halo masses in the range $6 \times 10^{13}M_\odot$ (massive groups) - $10^{15.5}M_\odot$ (Coma-like clusters). We analyse optical and infrared colours and stellar masses of BCGs as a function of the mass of their host haloes. We find that BCGs are mostly red and quiescent galaxies and that a minority ($\sim 9$\%) of them are star-forming. We find that the optical $g-r$ colours are consistent with those of red sequence galaxies at the same redshifts; however, we detect the presence of a tail of blue and mostly star-forming BCGs preferentially located in low-mass clusters and groups. Although the blue tail is dominated by star-forming galaxies, we find that star-forming BCGs may also have red $g-r$ colours, indicating dust-enshrouded star formation. The fraction of star-forming BCGs increases with redshift and decreases with cluster mass and BCG stellar mass. We find that cool-core clusters host both star-forming and quiescent BCGs; however, non cool-core clusters are dominated by quiescent BCGs. Star formation appears thus as the result of processes that depend on stellar mass, cluster mass and cooling state of the intra-cluster medium. Our results suggest no significant stellar mass growth at $z<0.35$, supporting the notion that BCGs had accreted most of their mass by $z = 0.35$. Overall we find a low (1\%) AGN fraction detected at IR wavelengths.

A 100 pc-scale fast and dense outflow in the narrow-line Seyfert 1 galaxy IRAS 04576+0912

Abstract We report the initial results of an adaptive-optics-assisted, optical integral-field-unit observation of IRAS 04576+0912, the nearest (z = 0.039) active galactic nucleus with a prominent blueshift/tail in [O iii] emission from a sample of such objects that we have collected from the literature. We aim at addressing the putative quasar-mode feedback process with Subaru/Kyoto 3D II+AO188. The optical waveband (6400–7500 Å) enables us to measure the gas density via the [S ii] doublets, in contrast to earlier near-IR studies. Since the fast [O iii] outflow happens only around rapidly growing central black holes, this object is suitable for investigating the black hole–galaxy coevolution. The obtained data cube exhibits a blue tail in the [S ii] emission at many lenslets. By fitting the spectrum with the high excess flux at the [S ii] bluetail, we find a fast (∼860 km s−1), dense (&amp;gt;3000 cm−3), wide-angle, and offset outflow in central 100 pc scales. Although the large opening angle and the high gas outflow-to-accretion ratio may favor the feedback hypothesis, the inferred kinetic power injection rate of this ionized gas outflow seems insufficient to influence the whole host galaxy. A conventional assumption of a low density must have overestimated the feedback process.

Visible-Spanning Flat Supercontinuum for Astronomical Applications

We demonstrate a broad, flat, visible supercontinuum spectrum that is generated by a dispersion-engineered tapered photonic crystal fiber pumped by a 1 GHz repetition rate turn-key Ti:sapphire laser outputting $\sim$ 30 fs pulses at 800 nm. At a pulse energy of 100 pJ, we obtain an output spectrum that is flat to within 3 dB over the range 490-690 nm with a blue tail extending below 450 nm. The mode-locked laser combined with the photonic crystal fiber forms a simple visible frequency comb system that is extremely well-suited to the precise calibration of astrophysical spectrographs, among other applications.

The Type Ia Supernova Color–Magnitude Relation and Host Galaxy Dust: A Simple Hierarchical Bayesian Model

Abstract Conventional Type Ia supernova (SN Ia) cosmology analyses currently use a simplistic linear regression of magnitude versus color and light curve shape, which does not model intrinsic SN Ia variations and host galaxy dust as physically distinct effects, resulting in low color–magnitude slopes. We construct a probabilistic generative model for the dusty distribution of extinguished absolute magnitudes and apparent colors as the convolution of an intrinsic SN Ia color–magnitude distribution and a host galaxy dust reddening–extinction distribution. If the intrinsic color–magnitude (M B versus B − V) slope differs from the host galaxy dust law R B , this convolution results in a specific curve of mean extinguished absolute magnitude versus apparent color. The derivative of this curve smoothly transitions from in the blue tail to R B in the red tail of the apparent color distribution. The conventional linear fit approximates this effective curve near the average apparent color, resulting in an apparent slope between and R B . We incorporate these effects into a hierarchical Bayesian statistical model for SN Ia light curve measurements, and analyze a data set of SALT2 optical light curve fits of 248 nearby SNe Ia at . The conventional linear fit gives . Our model finds and a distinct dust law of , consistent with the average for Milky Way dust, while correcting a systematic distance bias of ∼0.10 mag in the tails of the apparent color distribution. Finally, we extend our model to examine the SN Ia luminosity–host mass dependence in terms of intrinsic and dust components.

Embryonic developmental process governing the conspicuousness of body stripes and blue tail coloration in the lizard Plestiodon latiscutatus.

The combination of body stripes and vivid blue tail color has independently evolved in different lizard families. To understand how and when lizards developed this coloration, we microscopically compared the embryonic development of pigment cells in two island populations of Plestiodon latiscutatus that exhibit either striped and blue tailed or inconspicuously striped and blue tailed juveniles, based on the newly determined 12 normal developmental stages of embryos from shortly after egg laying to just before hatching. We focus on the role of the melanophores in the body stripe and the role of iridophore morphotypes in the extent of blue tail coloration. The melanophore density in the black background region was higher in lizards with vivid stripes than in lizards with drab stripes. Iridophores started to fill the dermal space that was not yet occupied by melanophores, which resulted in a higher iridophore density in stripes than in the inter-stripe regions. We also discovered that iridophores with thin platelets reflecting blue structural coloration appeared at a specific region in the tail at stage 11. The position of the tail where iridophores emerged coincided with the boundary area separating anterior brown and green colored tail from posterior blue colored tail after hatching.

Iridophore- and Xanthophore-Deficient Melanistic Color Variant of the LizardPlestiodon latiscutatus

Abstract: Elucidating the ultimate and proximate mechanisms of melanistic color pattern formation has become an important focus of evolutionary biology. There are relatively few studies, however, examining the composition and architecture of pigment cells in melanistic reptiles. The typical color pattern of the skink Plestiodon latiscutatus, which inhabits the Izu Islands and Izu Peninsula of Japan, consists of brown dorsal coloration, five vivid yellowish white stripes, and a blue tail (in juveniles). We have observed melanistic morphs at a low frequency (<0.05%). Based on a histological examination of pigment cells, we determined that the melanistic morph of P. latiscutatus collected from Shikine in the Izu Islands possesses only dermal melanophores and lacks the xanthophores and iridophores seen in the normal coloration. This arrangement of pigment cells differs from the only other studied melanistic lizard, Sceloporus undulatus, in which the dark skin of the melanistic morph results from a simple inc...

Cellular basis of anti‐predator adaptation in a lizard with autotomizable blue tail against specific predators with different colour vision

AbstractJuveniles of numerous lizard species have a vividly blue‐coloured tail that likely serves to deflect predator attacks toward the autotomizable tail rather than the lizard's body. The shades of blue colour in the tails of juvenile Plestiodon latiscutatus lizards vary across populations, most notably among those island populations with different predator assemblages. Here, we determine if this intraspecific variation is associated with the differences in colour vision capabilities of lizard predator species. If associated, it would be evidence for local adaptation of tail colour phenotype – natural selection is maximizing the conspicuousness of the tail to the dominant predator species to increase the chance of successfully deflecting attacks. We also use transmission electron microscopy (TEM) to determine the proximate cellular mechanisms that produce the shades of blue in different populations. We revealed that lizard tails with vivid blue reflectance evolved in communities with either weasel or snake predators, two groups of animals with the ability to detect blue wavelengths. However, lizard tail UV reflectance was much higher in populations with only snake predators; that snakes can detect UV, yet weasels cannot, suggests that high UV reflectance is an adaptation to increase tail conspicuousness specifically to snake predators. Finally, a cryptic brown tail evolved independently on the islands where birds are the primary lizard predator. We suggest that because birds have keen visual acuity; a brown, camouflaged phenotype is more advantageous. We also determined through TEM that the thickness of light reflecting platelets in iridophores, and densities of iridophores and xanthophores, predicted the wavelengths and intensity of light reflected by the lizard tail. For example, blue coloration was produced by selective reflection of short wavelengths of light by the thin light reflecting platelets of the iridophore. Greater iridophore density increased light reflectance, while greater xanthophore density decreased light reflectance.

Multiple Ornaments—Multiple Signaling Functions? The Importance of Song and UV Plumage Coloration in Female Superb Fairy-wrens (Malurus cyaneus)

Showy ornaments are considered as outcomes of sexual selection processes. They provide a “badge of status” to impress conspecific rivals or potential mating partners. Single ornaments may signal attractiveness or individual quality, yet many species display multiple ornaments. There are several hypotheses that explain the existence of multiple ornaments, suggesting that different ornaments serve as different information sources. They may provide either additive or redundant information on the same quality traits, or are simply evolutionary leftovers with no further relevant information. Although females of many species display elaborated traits, most studies regarding multiple ornaments focus on males. However, given that in many species females also display multiple ornaments, the question about their functional significance arises. To understand the existence of female multiple ornaments we investigated ornamental features of female Superb Fairy-wrens (Malurus cyaneus), focusing on song and variation in plumage characteristics. Female Superb Fairy-wrens produce complex solo songs, for territorial defense, and have bright blue tail feathers. We examined the relationships between song and plumage coloration characteristics in relation to female quality parameters to investigate whether, and to what extent existing hypotheses on multiple ornaments in males may also apply to females. Based on song recordings and spectrometric measurements of UV-coloration of tail feathers, we derived a series of different song and plumage parameters. Our results indicate interrelationships between the song length (total number of elements in female song) and female body size, but not UV-coloration. Interestingly, song complexity (number of different elements in female song) did not correlate with morphological parameters, UV-Chroma and song length respectively. This suggests that i) song and plumage characteristics evolved independently and ii) even within one trait, namely song, multiple signalling should be considered. To our knowledge, this is the first study investigating multiple traits in female songbirds, raising the idea that multiple signalling of sexually selected traits is not restricted to males only.

Skink on the Brink by L. Dalrymple

Dalrymple, Lisa. Skink on the Brink. Illus. Suzanne del Rizzo. Markham: Fitzhenry and Whiteside, 2013. Print.Stewie is a little skink, a member of an endangered species, and therefore very much “on the brink”. We meet young Stewie and his very blue tail as he enjoys life by a pond. Here in the forest he engages with other creatures, including a hungry weasel who pounces on him. The skink is safe, but his tail has popped off, leaving him free to escape the weasel’s clutches. Back grows the tail as beautiful as ever.However as Stewie grows he changes, and the beautiful blue tail is now a dull grey. Nothing feels right. Trying to escape the changes that are happening to him and mourning the loss of his blue tail, Stewie makes for a new pond. Here he meets a wise woodpecker who helps him to accept the changes in his colour as part of “growing up “. He sends Stewie back to his home pond, now more sure of himself and happy to be home.This gentle story of accepting the changes that growing up brings, and therefore accepting and loving yourself, is illustrated in lively pictures sculpted in modelling clay. The fine sense of texture and lively presentation complement the story well.Skink on the Brink won the SCBWI Crystal Kite Award (Canada) for 2014.Recommended: 3 out of 4 starsReviewer: Andrea DeakinAndrea has been involved with books since she was class librarian in Primary School, Student Librarian in Grammar School, student librarian for the Education Faculty when she was a student, and school librarian in schools both in England and in Canada, except for the first two years in Canada where she arrived in 1959. When she retired from teaching ( English and History) she was invited to review in February 1971, and continued to review for press, radio, and finally on the Internet (Deakin Newsletter from Okanagan College) until she retired in 2011. Forty years seemed sufficient- although she still cannot keep her nose out of good children's and YA fare.

Bite me: Blue tails as a ‘risky-decoy’ defense tactic for lizards

Abstract Many lizard species use caudal autotomy to escape entrapment. Conspicuous coloration may increase the likelihood of being attacked, but if that attack can be directed towards the autotomous tail this may ultimately increase the chances of the lizard surviving a predatory attack. We tested the hypothesis that brightly-colored tails function to divert predatory attention away from the head and body using pairs of blue-tailed and all-brown clay model lizards. Predatory bird attacks on the 24 blue-tailed models occurred sooner (P = 0.001) than attacks on the 24 all-brown models, and over 7 days blue-tailed models were attacked more often than all-brown models (P = 0.007). Blue-tailed models were, however, more frequently attacked on the tail than other parts of the body (P &amp;lt; 0.001), while all-brown models were more frequently attacked on the head and body (P = 0.019) which would be more likely to be fatal for a real lizard. Our results suggest that models with a blue tail were more conspicuous than all-brown models, attracting attacks sooner and more often, but that the attacks were predominantly directed at the tail. It is better for individuals to be attacked unsuccessfully many times, than successfully just once. Having a brightly-colored tail may, therefore, act as a ‘risky decoy’. Despite increased conspicuousness, a blue tail increases the likelihood that the lizard would be able to effect escape through caudal autotomy rather than being grabbed by the head or body.

The extreme chemistry of multiple stellar populations in the metal-poor globular cluster NGC 4833

Our FLAMES survey of Na-O anticorrelation in globular clusters (GCs) is extended to NGC 4833, a metal-poor GC with a long blue tail on the horizontal branch (HB). We present the abundance analysis for a large sample of 78 red giants based on UVES and GIRAFFE spectra acquired at the ESO-VLT. We derived abundances of Na, O, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Ba, La, Nd. This is the first extensive study of this cluster from high resolution spectroscopy. On the scale of our survey, the metallicity of NGC 4833 is [Fe/H]=-2.015+/-0.004+/-0.084 dex (rms=0.014 dex) from 12 stars observed with UVES, where the first error is from statistics and the second one refers to the systematic effects. The iron abundance in NGC 4833 is homogeneous at better than 6%. On the other hand, the light elements involved in proton-capture reactions at high temperature show the large star-to-star variations observed in almost all GCs studied so far. The Na-O anticorrelation in NGC 4833 is quite extended, as expected from the high temperatures reached by stars on the HB, and NGC 4833 contains a conspicuous fraction of stars with extreme [O/Na] ratios. More striking is the finding that large star-to-star variations are seen also for Mg, which spans a range of more than 0.5 dex in this GC. Depletions in Mg are correlated to the abundances of O and anti-correlated with Na, Al, and Si abundances. This pattern suggests the action of nuclear processing at unusually high temperatures, producing the extreme chemistry observed in the stellar generations of NGC 4833. This extreme changes are also seen in giants of the much more massive GCs M 54 and omega Cen, and our conclusion is that NGC 4833 has probably lost a conpicuous fraction of its original mass due to bulge shocking, as also indicated by its orbit.

Spectral Sensitivities and Color Signals in a Polymorphic Damselfly

Animal communication relies on conspicuous signals and compatible signal perception abilities. Good signal perception abilities are particularly important for polymorphic animals where mate choice can be a challenge. Behavioral studies suggest that polymorphic damselflies use their varying body colorations and/or color patterns as communication signal for mate choice and to control mating frequencies. However, solid evidence for this hypothesis combining physiological with spectral and behavioral data is scarce. We investigated this question in the Australian common blue tail damselfly, Ischnura heterosticta, which has pronounced female-limited polymorphism: andromorphs have a male-like blue coloration and gynomorphs display green/grey colors. We measured body color reflectance and investigated the visual capacities of each morph, showing that I. heterosticta have at least three types of photoreceptors sensitive to UV, blue, and green wavelength, and that this visual perception ability enables them to detect the spectral properties of the color signals emitted from the various color morphs in both males and females. We further demonstrate that different color morphs can be discriminated against each other and the vegetation based on color contrast. Finally, these findings were supported by field observations of natural mating pairs showing that mating partners are indeed chosen based on their body coloration. Our study provides the first comprehensive evidence for the function of body coloration on mate choice in polymorphic damselflies.

Una nueva especie de Liolaemus del grupo de L. nigromaculatus (Iguania: Liolaemidae) para la Región de Atacama, Chile

Here, we describe a new species of Liolaemus (Iguania: Liolaemidae) from the coastal desert of Atacama in the vicinity of Barranquilla, Chile. This new species belongs to the L. nigromaculatus group and can be distinguished from the other species of the group and the remaining species of the genus Liolaemus, by the striking color pattern of the male, with black head and dorsum, and light blue thighs and tail, as well as other scalation features that allow its diagnosis. With this new species, the L. nigromaculatus group increases to 13 species

The horizontal branch morphology of M 31 globular clusters

We use deep, high quality colour magnitude diagrams obtained with the Hubble Space Telescope to compute a simplified version of the Mironov index [SMI; B/(B+R)] to parametrize the horizontal branch (HB) morphology for 23 globular clusters in the M31 galaxy (Sample-A), all located in the outer halo at projected distances between 10 kpc and 100 kpc. This allows us to compare them with their Galactic counterparts, for which we estimated the SMI exactly in the same way, in the SMI vs. [Fe/H] plane. We find that the majority of the considered M31 clusters lie in a significantly different locus, in this plane, with respect to Galactic clusters lying at any distance from the center of the Milky Way. In particular they have redder HB morphologies at a given metallicity, or, in other words, clusters with the same SMI value are ~0.4 dex more metal rich in the Milky Way than in M31. We discuss the possible origin of this difference and we conclude that the most likely explanation is that many globular clusters in the outer halo of M31 formed ~1-2 Gyr later than their counterparts in the outer halo of the Milky Way, while differences in the cluster-to-cluster distribution of He abundance of individual stars may also play a role. The analysis of another sample of 25 bright M31 clusters (eighteen of them with M_V<= -9.0, Sample-B), whose SMI estimates are much more uncertain as they are computed on shallow colour magnitude diagrams, suggests that extended blue HB tails can be relatively frequent among the most massive M31 globular clusters, possibly hinting at the presence of multiple populations.

The fitness consequences of the autotomous blue tail in lizards: an empirical test of predator response using clay models

Numerous vertebrates employ one or more autotomous body parts as an anti-predation mechanism. Many lizards possess an autotomous tail that is brightly colored blue, which has been suggested to either serve as a decoy mechanism to divert predator attention to the autotomous body part, as an interspecific signal, or as an aposematic signal to predators that it is distasteful or dangerous. While theoretical studies suggest that a conspicuous autotomous body part that increases the probability of escape while not increasing the rate of detection will be favorable over a completely cryptic form, there is little empirical evidence supporting the adaptive benefit of an autotomous blue tail. We used in situ clay models of a scincid lizard to test the fitness consequences of blue coloration. Lizard models with a dark base color and blue decoy coloration experienced no measurable difference in avian predation relative to an all-dark model, which suggests that blue coloration neither serves as an aposematic signal nor increases the conspicuousness of the lizard model. Despite statistically similar attack rates, avian attacks on models with blue coloration were indeed focused on body sections that were colored blue. Our results suggest that the blue tail in lizards serves as an effective decoy, and that avian predation has possibly played a role in the evolution of the blue tail.

Analytic Theory of the Resonance Properties of Metallic Nanoslit Arrays

By applying formulation based on time reversibility, we provide the analytic theory of resonance properties of metallic nanoslit arrays. We model lossy resonant systems in which a resonance is induced by a single quasi-bound mode (QBM). It is consistent with the Fano resonance theory of quantum interference of auto-ionizing atoms and captures the essential characteristics of dissipative resonant systems. We show that time-reversibility requirements lead to analytical solutions for the resonant transmission and the associated nonreciprocal absorption in terms of a minimal number of independent basic parameters that include partial decay probabilities of resonant pathways and the non-resonant transmission amplitude. With a clear view of interfering electromagnetic field configurations and the associated absorbing processes, the theory reveals the essential physics of resonant optical transmission. In particular, the enhanced transmission peak is given by the product of partial decay probabilities and is independent of the non-resonant light wave amplitude. In a highly asymmetric coupling regime, the excitation of the QBM leads to anti-resonant extinction of the transmission, indicating a negative role of the QBM. The parity of the QBM determines occurrence of red or blue tails in the spectral profile. Absorbance measurements yield direct determination of the partial decay probabilities by which the main features of the resonant transmission are quantitatively explained. Thus, these basic parameters can be directly established experimentally. Full numerical calculations of the transmission spectra are in complete quantitative agreement with our analytical formulation for optical transmission mediated by both slit cavity modes and plasmonic modes.

Kingfisher feathers – colouration by pigments, spongy nanostructures and thin films

The colours of the common kingfisher, Alcedo atthis, reside in the barbs of the three main types of feather: the orange breast feathers, the cyan back feathers and the blue tail feathers. Scanning electron microscopy showed that the orange barbs contain small pigment granules. The cyan and blue barbs contain spongy nanostructures with slightly different dimensions, causing different reflectance spectra. Imaging scatterometry showed that the pigmented barbs create a diffuse orange scattering and the spongy barb structures create iridescence. The extent of the angle-dependent light scattering increases with decreasing wavelength. All barbs have a cortical envelope with a thickness of a few micrometres. The reflectance spectra of the cortex of the barbs show oscillations when measured from small areas, but when measured from larger areas the spectra become wavelength independent. This can be directly understood with thin film modelling, assuming a somewhat variable cortex thickness. The cortex reflectance appears to be small but not negligible with respect to the pigmentary and structural barb reflectance.

An observer's view of simulated galaxies: disc-to-total ratios, bars and (pseudo-)bulges

Abstract We use cosmological hydrodynamical simulations of the formation of Milky Way-mass galaxies to study the relative importance of the main stellar components, i.e. discs, bulges and bars, at redshift zero. The main aim of this Letter is to understand if estimates of the structural parameters of these components determined from kinematics (as is usually done in simulations) agree well with those obtained using a photometric bulge/disc/bar decomposition (as done in observations). To perform such a comparison, we have produced synthetic observations of the simulation outputs with the Monte Carlo radiative transfer code sunrise and used the budda code to make 2D photometric decompositions of the resulting images (in the i and g bands). We find that the kinematic disc-to-total (D/T) ratio estimates are systematically and significantly lower than the photometric ones. While the maximum D/T ratios obtained with the former method are of the order of 0.2, they are typically &amp;gt;0.4, and can be as high as 0.7, according to the latter. The photometric decomposition shows that many of the simulated galaxies have bars, with Bar/T ratios in the range 0.2–0.4, and that bulges have in all cases low Sérsic indices, resembling observed pseudo-bulges instead of classical ones. Simulated discs, bulges and bars generally have similar g−i colours, which are in the blue tail of the distribution of observed colours. This is not due to the presence of young stars, but rather due to low metallicities and poor gas content in the simulated galaxies, which makes dust extinction low. Photometric decompositions thus match the component ratios usually quoted for spiral galaxies better than kinematic decompositions, but the shift is insufficient to make the simulations consistent with observed late-type systems.

Polarization-Bound Quasi-Continuum States Are Responsible for the “Blue Tail” in the Optical Absorption Spectrum of the Aqueous Electron

The electronic absorption spectrum of the aqueous electron in bulk water has been simulated using long-range-corrected time-dependent density functional theory as well as mixed quantum/classical molecular dynamics based on a one-electron model in which electron-water polarization is treated self-consistently. Both methodologies suggest that the high-energy Lorentzian tail that is observed experimentally arises mostly from delocalized bound-state excitations of the electron rather than bound-to-continuum excitations, as is usually assumed. Excited states in the blue tail are bound only by polarization of the solvent electron density. These findings have potentially important ramifications for understanding electron localization in polar condensed media as well as biological radiation damage arising from dissociative electron attachment.

Mountant-induced loss of Shorr-stained blue sperm tails

It has been reported that Shorr staining provides additional morphological information on the motility of spermatozoa in semen, by distinguishing between red and blue flagella. With our routine methods (involving mounting slides) we were unable to confirm these observations. The presence of both red- and blue-coloured sperm tails in Shorr-stained semen smears was apparent, however, if slides were unmounted. Only a very weak association between blue flagellar staining and immotility was observed. Stating whether a mountant was used should be reported.