NIR Colors Research Articles

A spectrophotometric analysis and dust properties of classical nova V5584 Sgr

ABSTRACT In this work, optical observations of the nova V5584 Sgr are presented. These observations cover different phases including pre-maximum, early decline, and nebular. The spectra are dominated by hydrogen Balmer, Fe ii, and O i lines with P-Cygni profiles in the early phase, which are subsequently observed in complete emission. The presence of numerous Fe ii lines and low ejecta velocity aligns with the Fe ii type nova classification. From optical and NIR colours, it is clear that this nova manifests dust formation in the ejecta. The dust temperature and mass were estimated from a spectral energy distribution (SED) fit to the JHK band magnitudes and the Wide field Infrared Survey Explorer data. Light-curve analysis shows t$_2$ and t$_3$ values of $\sim$ 26 and $\sim$ 48 d, classifying the nova as moderately fast. The physical and chemical properties during early decline and later phases were evaluated using the photoionization code CLOUDY. The best-fitting model parameters from two epochs of multiwavelength spectra are compatible with a hot white dwarf source with a roughly constant luminosity of $\sim$(2.08 $\pm$ 0.10) $\times$ 10$^{36}$ erg s$^{-1}$. We find an ejected mass of $\sim$(1.59 $\pm$ 0.04) $\times$ 10$^{-4}$ M$_{\odot }$. Abundance analysis indicates that the ejecta is significantly enriched relative to solar values, with O/H = 30.2, C/H = 10.8, He/H = 1.8, Mg/H = 1.68, Na/H = 1.55, and N/H = 45.5 in the early decline phase, and O/H = 4.5, Ne/H = 1.5, and N/H = 24.5 in the nebular phase.

Diagnosing Fungal Infection in Wheat Kernels by Integrating Spectroscopic Technology and Digital Color Imaging System: Artificial Neural Network, Principal Component Analysis and Correlation Feature Selection Techniques

ABSTRACTContamination of cereal grain, especially wheat, with fungal infections can cause significant economic impacts and it endangers the health of humans and livestock. This study aims to appraise the UV/VIS–NIR and digital color (RGB) imaging systems and spectroscopic methodology to detect wheat kernels infected by fungi such as Penicillium expansum and Fusarium graminearum. NIR spectra of 190–1100 nm at 10 nm intervals, visible color reflectance images and non‐visible reflectance images of wheat kernels in the ultraviolet and near‐infrared ranges were applied to develop the multi‐layer perceptron (MLP) artificial neural network model. The optimum wavelengths were selected by application of the principal component analysis (PCA) after preprocessing the raw spectra. A confusion matrix was used in the correlation feature selection method (CFS) for the decision tree classifier of selected features. The results showed that the four UV wavelengths of 310, 330, 400, and 410 nm were the best wavelengths using PCA to distinguish healthy and unhealthy wheat kernels. Considering the intensity of the wavelengths as the neural network inputs, samples were classified into healthy and unhealthy categories with an accuracy of 90.9%. Also, 18 features of color images in RGB, LAB, HSV, HSI, YCbCr, and YIQ spaces provided the highest average accuracy of 44.4% in classifying healthy and infected wheat kernels by using a CCD Proline camera in the ultraviolet range. In contrast, other cameras in the visible and invisible range showed low accuracy. Furthermore, the best classification accuracy of the healthy and infected samples by the use of the CFS method was obtained at 88.1%. Based on the findings, spectroscopic methodology proved to be highly effective for detecting, classifying and automatic cleaning of various agricultural seeds, with a particular emphasis on wheat kernals.

Discovery of an Apparent Red, High-velocity Type Ia Supernova at z = 2.9 with JWST

We present the James Webb Space Telescope (JWST) discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS+53.13485−27.82088 with a host spectroscopic redshift of 2.903 ± 0.007. The transient was identified in deep (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic follow-up with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (c ∼ 0.9) despite a host galaxy with low extinction and has a high Ca ii velocity (19,000 ± 2000 km s−1) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-z Ca-rich population. Although such an object is too red for any low-z cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (≲1σ) with ΛCDM. Therefore unlike low-z Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high z truly diverge from their low-z counterparts and to confirm that standardized luminosities nevertheless remain constant with redshift.

The Hawaii Infrared Parallax Program. VI. The Fundamental Properties of 1000+ Ultracool Dwarfs and Planetary-mass Objects Using Optical to Mid-infrared Spectral Energy Distributions and Comparison to BT-Settl and ATMO 2020 Model Atmospheres

We derive the bolometric luminosities (L bol) of 865 field-age and 189 young ultracool dwarfs (spectral types M6–T9, including 40 new discoveries presented here) by directly integrating flux-calibrated optical to mid-infrared (MIR) spectral energy distributions (SEDs). The SEDs consist of low-resolution (R ∼ 150) near-infrared (NIR; 0.8–2.5μm) spectra (including new spectra for 97 objects), optical photometry from the Pan-STARRS1 survey, and MIR photometry from the CatWISE2020 survey and Spitzer/IRAC. Our L bol calculations benefit from recent advances in parallaxes from Gaia, Spitzer, and UKIRT, as well as new parallaxes for 19 objects from CFHT and Pan-STARRS1 presented here. Coupling our L bol measurements with a new uniform age analysis for all objects, we estimate substellar masses, radii, surface gravities, and effective temperatures (T eff) using evolutionary models. We construct empirical relationships for L bol and T eff as functions of spectral type and absolute magnitude, determine bolometric corrections in optical and infrared bandpasses, and study the correlation between evolutionary model-derived surface gravities and NIR gravity classes. Our sample enables a detailed characterization of BT-Settl and ATMO 2020 atmospheric model systematics as a function of spectral type and position in the NIR color–magnitude diagram. We find the greatest discrepancies between atmospheric and evolutionary model-derived T eff (up to 800 K) and radii (up to 2.0 R Jup) at the M/L spectral type transition boundary. With 1054 objects, this work constitutes the largest sample to date of ultracool dwarfs with determinations of their fundamental parameters.

Development of 4-μm-pixel Pitch NIR Multispectral Imaging Sensor and Its Application to Glare-free NIR Color Fundus Camera

Development of 4-μm-pixel Pitch NIR Multispectral Imaging Sensor and Its Application to Glare-free NIR Color Fundus Camera

Early JWST Imaging Reveals Strong Optical and NIR Color Gradients in Galaxies at z ∼ 2 Driven Mostly by Dust

Recent studies have shown that galaxies at cosmic noon are redder in the center and bluer in the outskirts, mirroring results in the local universe. These color gradients could be caused by gradients in either the stellar age or dust opacity; however, distinguishing between these two causes is impossible with rest-frame optical photometry alone. Here we investigate the underlying causes of the gradients from spatially resolved rest-frame U − V versus V − J color–color diagrams measured from early observations with the James Webb Space Telescope. We use 1–4 μm NIRCam photometry from the CEERS survey of a sample of 54 galaxies with at redshifts 1.7 < z < 2.3 selected from the 3D-HST catalog. We model the light profiles in the F115W, F200W, and F356W NIRCam bands using imcascade, a Bayesian implementation of the multi-Gaussian expansion technique that flexibly represents galaxy profiles using a series of Gaussians. We construct resolved rest-frame U − V and V − J color profiles. The majority of star-forming galaxies have negative gradients (i.e., redder in the center, bluer in the outskirts) in both U − V and V − J colors consistent with radially decreasing dust attenuation. A smaller population (roughly 15%) of star-forming galaxies have positive U − V but negative V − J gradients implying centrally concentrated star formation. For quiescent galaxies, we find a diversity of UVJ color profiles, with roughly one-third showing star formation in their center. This study showcases the potential of JWST to study the resolved stellar populations of galaxies at cosmic noon.

Shaping physical properties of galaxy subtypes in the VIPERS survey: Environment matters

Aims. This study aims to explore the relation between the physical properties of different galaxy sub-classes, from red passive to blue star-forming, and their environment. Our work is based on the analysis of 31 631 galaxies from the VIMOS Public Extragalactic Redshift Survey (VIPERS), observed at 0.5 &lt; z &lt; 0.9. The unprecedented volume of VIPERS and the wealth of auxiliary derived data allow us to associate sub-classes of the main galaxy populations with their possibly different evolutionary paths. This is the first time such a study is performed with such statistical precision. Methods. We use the results of an unsupervised clustering algorithm to distinguish 11 subclasses of VIPERS galaxies, based on the multi-dimensional feature space, defined by rest-frame UV to NIR colours. We investigate the relationship between the properties of these sub-classes of galaxies and their local environment, defined as the galaxy density contrast, δ, derived from the fifth nearest neighbour technique. Results. We confirm that the galaxy population-density relation is already in place at z ∼ 0.9, with the blue galaxy fraction decreasing with density, compensated by an increase in the red fraction. We demonstrate how the properties of red, green, and blue galaxy subclasses are altered as they assemble into denser regions, and we attempt to interpret this in the context of their evolution. On average, red galaxies in the high-density environment are larger by 28% than those in low-density environments. In particular, we find one group of galaxies, sub-class C3, whose increase of size with time can be explained mainly as the result of mergers; for other red subclasses, mergers would not seem to play the major role (subclass C2) or would play a negligible role (sub-class C1). The properties of the green galaxies (sub-classes C4–6) depend on whether their stellar mass is above or below a transition mass, log(Mstar/M⊙)=10.6. Low-mass green (9.5 ≲ log(Mstar/M⊙)≲10.6) galaxies appear to have grown through secular processes, while in high-mass (10.6 ≲ log(Mstar/M⊙)≲11.5) green galaxies, mass assembly appears to be dominated by mergers. When it comes to blue galaxies, the trend of decreasing fraction with denser environments seen for the group as a whole (sub-classes C7–11) is found to be driven mostly by one (the most numerous) group of galaxies; sub-class C10. These are compact low-mass galaxies with high, specific star formation rates, which are preferentially found in low-density environments. However, the remaining blue galaxies (sub-classes C7–9) are larger and appear in denser environments than galaxies within C10.

Predicting the Spectrum of UGC 2885, Rubin’s Galaxy with Machine Learning

Abstract Wu &amp; Peek predict SDSS-quality spectra based on Pan-STARRS broadband grizy images using machine learning (ML). In this article, we test their prediction for a unique object, UGC 2885 (“Rubin’s galaxy”), the largest and most massive, isolated disk galaxy in the local universe (D &lt; 100 Mpc). After obtaining the ML predicted spectrum, we compare it to all existing spectroscopic information that is comparable to an SDSS spectrum of the central region: two archival spectra, one extracted from the VIRUS-P observations of this galaxy, and a new, targeted MMT/Binospec observation. Agreement is qualitatively good, though the ML prediction prefers line ratios slightly more toward those of an active galactic nucleus (AGN), compared to archival and VIRUS-P observed values. The MMT/Binospec nuclear spectrum unequivocally shows strong emission lines except Hβ, the ratios of which are consistent with AGN activity. The ML approach to galaxy spectra may be a viable way to identify AGN supplementing NIR colors. How such a massive disk galaxy (M* = 1011 M ⊙), which uncharacteristically shows no sign of interaction or mergers, manages to fuel its central AGN remains to be investigated.

Abandoned Land Classification Using Classical Theory Method

According to the official statistics the areas of abandoned agricultural land in Lithuania are gradually decreasing, but very slightly. The aim of this study is to research spatial determination and abandoned land classification in the territory of Vilnius District Municipality. Vilnius District Municipality was chosen for the research because it, although located near the capital of the country and has a high population density, it is still the district having the largest percent of abandoned land plots. A fast, cost-effective and sufficiently accurate method for determination of abandoned land plots would allow to constantly monitor, to fix changes and foresee the abandoned land plots reduction possibilities. In the study there was used the multispectral RGB and NIR color Sentinel-2 satellite images, the layer of the administrative boundary of Vilnius County and layer of abandoned agriculture land, which is available in Lithuanian Spatial Information Portal (www.geoportal.lt). The data was processed by Geographic Information System (GIS) techniques using classical classification Region Growing Algorithm. The research shows that NIR image classification result is more reliable than the result from RGB images.

Preliminary high-throughput phenotyping analysis in grapevines under drought

This study reports correlative information between leaf water potential (ψ), total leaf area of draughted grapevines (Vitis vinifera L.) and non-destructive image analysis techniques. Four groups of 20 potted vines each were subjected to various irrigation treatments restoring 100% (control), 75%, 50% and 25% of daily water consumption within a 22-day period of drought imposition. Leaf gas exchanges (Li-Cor 6400), ψ (Scholander chamber), fluorescence (PAM − 2500), RGB and NIR (Scanalyzer 3D system, LemnaTec GmbH phenotyping platform) data were collected before and at the end of drought imposition. Values of ψ in severely stressed vines (25%) reached −1.2 MPa pre-dawn, in turn stomatal conductance and photosynthesis reached values as low as approx. 0.02 mol H2O m−2 s−1 and 1.0 μmol CO2 m−2 s−1, respectively. The high-throughput analysis preliminarily revealed a correlation between ψ (stem) and NIR Color Class (R2=0.80), and that plant leaf area might be accurately estimated through imagine analysis (R2=0.90).

Deep Extragalactic VIsible Legacy Survey (DEVILS): motivation,design, and target catalogue

The Deep Extragalactic VIsible Legacy Survey (DEVILS) is a large spectroscopic campaign at the Anglo-Australian Telescope (AAT) aimed at bridging the near and distant Universe by producing the highest completeness survey of galaxies and groups at intermediate redshifts ($0.3<z<1.0$). Our sample consists of $\sim$60,000 galaxies to Y$<$21.2mag, over $\sim$6deg$^{2}$ in three well-studied deep extragalactic fields (Cosmic Origins Survey field, COSMOS, Extended Chandra Deep Field South, ECDFS and the X-ray Multi-Mirror Mission Large-Scale Structure region, XMM-LSS - all Large Synoptic Survey Telescope deep-drill fields). This paper presents the broad experimental design of DEVILS. Our target sample has been selected from deep Visible and Infrared Survey Telescope for Astronomy (VISTA) Y-band imaging (VISTA Deep Extragalactic Observations, VIDEO and UltraVISTA), with photometry measured by ProFound. Photometric star/galaxy separation is done on the basis of NIR colours, and has been validated by visual inspection. To maximise our observing efficiency for faint targets we employ a redshift feedback strategy, which continually updates our target lists, feeding back the results from the previous night's observations. We also present an overview of the initial spectroscopic observations undertaken in late 2017 and early 2018.

CLUSTERING OF EXTREMELY RED OBJECTS IN THE SUBARU GTO 2DEG2 FIELD

We study the angular correlation function of bright (<TEX>$K_s{\leq}19.5$</TEX>) Extremely Red Objects (EROs) selected in the Subaru GTO 2<TEX>$deg^2$</TEX> field. By applying the color selection criteria of <TEX>$R-K_s$</TEX> > 5.0, 5.5, and 6.0, we identify 9055, 4270, and 1777 EROs, respectively. The number density is consistent with similar studies on the optical - NIR color selected red galaxies. The angular correlation functions are derived for EROs with different limiting magnitude and different <TEX>$R-K_s$</TEX> color cut. When we assume that the angular correlation function <TEX>$w({\theta})$</TEX> follows a form of a power-law (i.e., <TEX>$w({\theta})=A{\theta}^{-{\delta}}$</TEX>), the value of the amplitude A was larger for brighter EROs compared to the fainter EROs. The result suggests that the brighter, thus more massive high-redshift galaxies, are clustered more strongly compared to the less massive galaxies. Assuming that EROs have redshift distribution centered at <z> ~ 1.1 with <TEX>${\sigma}_z=0.15$</TEX>, the spatial correlation length <TEX>$r_0$</TEX> of the EROs estimated from the observed angular correlation function ranges <TEX>${\sim}6-10h^{-1}Mpc$</TEX>. A comparison with the clustering of dark matter halos in numerical simulation suggests that the EROs are located in most massive dark matter halos and could be progenitors of <TEX>$L_{\ast}$</TEX> elliptical galaxies.

Spectroscopic investigation on europium doped heavy metal borate glasses for red luminescent application

The present study explores a new borate family glasses based on 10ZnO–5Na2O–10Bi2O3–(75 − x) B2O3–xEu2O3 (x = 0, 0.1, 0.5, 1, 1.5, 2, 3 mol%) composition, synthesized by rapid melt quench technique. Prepared glasses were subjected to the density and refractive index measurements and their values were used to calculate other physical properties of the glass matrix as a function of Eu3+ concentration. XRD confirmed amorphous nature of the glasses. FTIR spectra in the absorption mode were recorded in the 400–4000 cm−1 region to identify different functional groups in the glass matrix. Deconvoluted FTIR spectra showed increase in BO4 units with rise in europium content which confirmed the ‘network strengthener’ role of europium ions by creating bridging oxygens (BOs). Optical properties were investigated for their luminescence behavior through various spectroscopic techniques such as UV–Vis–NIR absorption, excitation, emission, decay profiles, and color measurements at room temperature. Lasing properties of the glasses like total radiative life time, branching ratio, emission cross section, and optical gain were obtained from the calculated Judd–Ofelt (Ω2,Ω4) intensity parameters. From the measured values of emission, cross sections, branching ratios, life times, strong photoluminescence features, and CIE chromaticity coordinates, 0.5 mol% of Eu3+ ions doped ZnNaBiB glasses showed optimum performance and are potential candidate for red light generation at 613 nm.

Constraining dust properties in circumstellar envelopes of C-stars in the Small Magellanic Cloud: optical constants and grain size of carbon dust

We present a new approach aimed at constraining the typical size and optical properties of carbon dust grains in Circumstellar envelopes (CSEs) of carbon-rich stars (C-stars) in the Small Magellanic Cloud (SMC). To achieve this goal, we apply our recent dust growth description, coupled with a radiative transfer code to the CSEs of C-stars evolving along the TP-AGB, for which we compute spectra and colors. Then we compare our modeled colors in the near- and mid-infrared (NIR and MIR) bands with the observed ones, testing different assumptions in our dust scheme and employing several data sets of optical constants for carbon dust available in the literature. Different assumptions adopted in our dust scheme change the typical size of the carbon grains produced. We constrain carbon dust properties by selecting the combination of grain size and optical constants which best reproduces several colors in the NIR and MIR at the same time. The different choices of optical properties and grain size lead to differences in the NIR and MIR colors greater than two magnitudes in some cases. We conclude that the complete set of observed NIR and MIR colors are best reproduced by small grains, with sizes between $\sim$0.035 and $\sim$0.12~$\mu$m, rather than by large grains between $\sim0.2$ and $0.7$~$\mu$m. The inability of large grains to reproduce NIR and MIR colors seems independent of the adopted optical data set. We also find a possible trend of the grain size with mass-loss and/or carbon excess in the CSEs of these stars.

Single stellar populations in the near-infrared

We present a detailed study of the stars of the IRTF spectral library to understand its full extent and reliability for use with Stellar Population (SP) modeling. The library consist of 210 stars, with a total of 292 spectra, covering the wavelength range of 0.94 to 2.41 micron at a resolution R = 2000. For every star we infer the effective temperature (Teff), gravity (logg) and metallicity ([Z/Zsun]) using a full-spectrum fitting approach in a section of the K band (2.19 to 2.34 micron) and temperature-NIR colour relations. We test the flux calibration of these stars by calculating their integrated colours and comparing them with the Pickles library colour-temperature relations. We also investigate the NIR colours as a function of the calculated effective temperature and compared them in colour-colour diagrams with the Pickles library. This latter test shows a good broad-band flux calibration, important for the SP models. Finally, we measure the resolution R as a function of wavelength. We find that the resolution increases as a function of lambda from about 6 angstrom in J to 10 angstrom in the red part of the K-band. With these tests we establish that the IRTF library, the largest currently available general library of stars at intermediate resolution in the NIR, is an excellent candidate to be used in stellar population models. We present these models in the next paper of this series.

Tracing the tidal streams of the Sagittarius dSph, and halo Milky Way features, with carbon-rich long-period variables

We assemble 121 spectroscopically-confirmed halo carbon stars, drawn from the literature, exhibiting measurable variability in the Catalina Surveys. We present their periods and amplitudes, which are used to estimate distances from period-luminosity relationships. The location of the carbon stars - and their velocities when available - allow us to trace the streams of the Sagittarius (Sgr) dwarf spheroidal galaxy. These are compared to a canonical numerical simulation of the accretion of Sgr. We find that the data match this model well for heliocentric distances of 15-50 kpc, except for a virtual lack of carbon stars in the trailing arm just north of the Galactic Plane, and there is only tentative evidence of the leading arm south of the Plane. The majority of the sample can be attributed to the Sgr accretion. We also find groups of carbon stars which are not part of Sgr; most of which are associated with known halo substructures. A few have no obvious attribution and may indicate new substructure. We find evidence that there may be a structure behind the Sgr leading stream apocentre, at ~100 kpc, and a more distant extension to the Pisces Overdensity also at ~100 kpc. We study a further 75 carbon stars for which no good period data could be obtained, and for which NIR magnitudes and colours are used to estimate distances. These data add support for the features found at distances beyond 100 kpc.

THEHUBBLEWIDE FIELD CAMERA 3 TEST OF SURFACES IN THE OUTER SOLAR SYSTEM: SPECTRAL VARIATION ON KUIPER BELT OBJECTS

Here we present additional photometry of targets observed as part of the Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System. 12 targets were re-observed with the Wide Field Camera 3 in optical and NIR wavebands designed to compliment those used during the first visit. Additionally, all observations originally presented by Fraser and Brown (2012) were reanalyzed through the same updated photometry pipeline. A reanalysis of the optical and NIR colour distribution reveals a bifurcated optical colour distribution and only two identifiable spectral classes, each of which occupies a broad range of colours and have correlated optical and NIR colours, in agreement with our previous findings. We report the detection of significant spectral variations on 5 targets which cannot be attributed to photometry errors, cosmic rays, point spread function or sensitivity variations, or other image artifacts capable of explaining the magnitude of the variation. The spectrally variable objects are found to have a broad range of dynamical classes, absolute magnitudes, exhibit a broad range of apparent magnitude variations, and are found in both compositional classes. The spectrally variable objects with sufficiently accurate colours for spectral classification maintain their membership, belonging to the same class at both epochs. 2005 TV189 exhibits a sufficiently broad difference in colour at the two epochs that span the full range of colours of the neutral class. This strongly argues that the neutral class is one single class with a broad range of colours, rather than the combination of multiple overlapping classes.

RECONSTRUCTING THE STELLAR MASS DISTRIBUTIONS OF GALAXIES USING S4G IRAC 3.6 AND 4.5 μm IMAGES. II. THE CONVERSION FROM LIGHT TO MASS

We present a new approach for estimating the 3.6 micron stellar mass-to-light ratio in terms of the [3.6]-[4.5] colors of old stellar populations. Our approach avoids several of the largest sources of uncertainty in existing techniques. By focusing on mid-IR wavelengths, we gain a virtually dust extinction-free tracer of the old stars, avoiding the need to adopt a dust model to correctly interpret optical or optical/NIR colors normally leveraged to assign M/L. By calibrating a new relation between NIR and mid-IR colors of GLIMPSE giant stars we also avoid discrepancies in model predictions for the [3.6]-[4.5] colors of old stellar populations due to uncertainties in molecular line opacities. We find that the [3.6]-[4.5] color, which is driven primarily by metallicity, provides a tight constraint on M/L_3.6, which varies intrinsically less than at optical wavelengths. The uncertainty on M/L_3.6 of ~0.07 dex due to unconstrained age variations marks a significant improvement on existing techniques for estimating the stellar M/L with shorter wavelength data. A single M/L_3.6=0.6 (assuming a Chabrier IMF), independent of [3.6]-[4.5] color, is also feasible as it can be applied simultaneously to old, metal-rich and young, metal-poor populations, and still with comparable (or better) accuracy (~0.1 dex) as alternatives. We expect our M/L_3.6 to be optimal for mapping the stellar mass distributions in S4G galaxies, for which we have developed an Independent Component Analysis technique to first isolate the old stellar light at 3.6 micron from non-stellar emission (e.g. hot dust and the 3.3 PAH feature). Our estimate can also be used to determine the fractional contribution of non-stellar emission to global (rest-frame) 3.6 micron fluxes, e.g. in WISE imaging, and establishes a reliable basis for exploring variations in the stellar IMF.

NEW 2MASS NEAR-INFRARED PHOTOMETRY FOR GLOBULAR CLUSTERS IN M31

We present Two Micron All Sky Survey JHKs photometry for 913 star clusters and candidates in the field of M31, which are selected from the latest Revised Bologna Catalog of M31 globular clusters (GCs) and candidates. The photometric measurements in this paper supplement this catalog, and provide the most comprehensive and homogeneous photometric catalog for M31 GCs in the JHKs bandpasses. In general, our photometry is consistent withpreviousmeasurements.Theglobularclusterluminosityfunction(GCLF)peaksfortheconfirmedGCsderived by fitting a t5 distribution using the maximum likelihood method are J0 = 15.348 +0.206 −0.208 , H0 = 14.703 +0.176 −0.180 , and Ks0 = 14.534 +0.142 −0.146 , all of which agree well with previous studies. The GCLFs are different between metal-rich (MR) and metal-poor (MP), and between inner and outer subpopulations, as MP clusters are fainter than their MR counterparts and the inner clusters are brighter than the outer ones, which confirm previous results. The NIR colors of the GC candidates are on average redder than those of the confirmed GCs, which leads to an obscure bimodal distribution of color indices. The relation of (V − Ks)0 and metallicity shows a notable departure from linearity, with a shallower slope toward the redder end. The color‐magnitude diagram (CMD) and color‐color diagram show that many GC candidates are located out of the evolutionary tracks, suggesting that some of them may be false M31 GC candidates. The CMD also shows that the initial mass function of M31 GCs covers a large range, and the majority of the clusters have initial masses between 10 3 and 10 6 M� .

CLASH: z ∼ 6 young galaxy candidate quintuply lensed by the frontier field cluster RXC J2248.7−4431

We present a quintuply lensed z ~ 6 candidate discovered in the field of the galaxy cluster RXC J2248.7-4431 (z ~ 0.348) targeted within the Cluster Lensing and Supernova survey with Hubble (CLASH) and selected in the deep HST Frontier Fields survey. Thanks to the CLASH 16-band HST imaging, we identify the quintuply lensed z ~ 6 candidate as an optical dropout in the inner region of the cluster, the brightest image having magAB=24.81+-0.02 in the f105w filter. We perform a detailed photometric analysis to verify its high-z and lensed nature. We get as photometric redshift z_phot ~ 5.9, and given the extended nature and NIR colours of the lensed images, we rule out low-z early type and galactic star contaminants. We perform a strong lensing analysis of the cluster, using 13 families of multiple lensed images identified in the HST images. Our final best model predicts the high-z quintuply lensed system with a position accuracy of 0.8''. The magnifications of the five images are between 2.2 and 8.3, which leads to a delensed UV luminosity of L_1600 ~ 0.5L*_1600 at z=6. We also estimate the UV slope from the observed NIR colours, finding a steep beta=-2.89+-0.38. We use singular and composite stellar population SEDs to fit the photometry of the hiz candidate, and we conclude that it is a young (age <300 Myr) galaxy with mass of M ~ 10^8Msol, subsolar metallicity (Z<0.2Zsol) and low dust content (AV ~ 0.2-0.4).