Vatican Advanced Technology Telescope Research Articles

An insight into Capella (α Aurigae): From the extent of core overshoot to its evolutionary history

Context. The binary star α Aurigae (otherwise known as Capella) is extremely important to understanding the core hydrogen and helium burning phases of stars, as its primary star is likely evolving through the core helium burning phase. Moreover, the masses of the star’s two components are ∼2.5 M⊙ and ∼2.6 M⊙, meaning they fall into a mass range in which the extension of the core overshoot during the main sequence phase is uncertain. Aims. We aim to derive the extent of the core overshoot experienced during the core burning phases and to test the efficiency of the convective transport of energy in the external envelope of Capella by comparing results from stellar evolution modelling with the results from observations. Methods. We considered evolutionary tracks calculated expressly for the present work, that is, for the primary and secondary stars of Capella. We determined the extent of the extra mixing from the core during the main sequence evolution and the age of the system by requiring that the effective temperatures and surface gravities of the model stars reproduce those derived from the observations at the same epoch. We further checked the consistency between the observed and predicted surface chemistry of the stars. Results. The consistency between results from stellar evolution modelling and the observations of Capella is found when extra mixing from the core is assumed, the extent of the extra-mixed zone being of the order of 0.25 HP. The age of the system is estimated to be 710 Myr. These results allow the observed surface chemistry to be well reproduced, particularly the recent determination of the 12C/13C ratio based on Large Binocular Telescope and Vatican Advanced Technology Telescope observations.

VPNEP: Detailed characterization of TESS targets around the Northern Ecliptic Pole

Context.We embarked on a high-resolution optical spectroscopic survey of bright Transiting Exoplanet Survey Satellite (TESS) stars around the Northern Ecliptic Pole (NEP), dubbed the Vatican-Potsdam-NEP (VPNEP) survey.Aims.Our NEP coverage comprises ≈770 square degrees with 1067 stars, of which 352 are bona fide dwarf stars and 715 are giant stars, all cooler than spectral type F0 and brighter thanV= 8m.5. Our aim is to characterize these stars for the benefit of future studies in the community.Methods.We analyzed the spectra via comparisons with synthetic spectra. Particular line profiles were analyzed by means of eigenprofiles, equivalent widths, and relative emission-line fluxes (when applicable).Results.TwoR= 200 000 spectra were obtained for each of the dwarf stars with the Vatican Advanced Technology Telescope (VATT) and the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI), with typically threeR= 55 000 spectra obtained for the giant stars with STELLA and the STELLA Echelle Spectrograph (SES). Combined withV-band magnitudes,GaiaEDR3 parallaxes, and isochrones from the Padova and Trieste Stellar Evolutionary Code, the spectra can be used to obtain radial velocities, effective temperatures, gravities, rotational and turbulence broadenings, stellar masses and ages, and abundances for 27 chemical elements, as well as isotope ratios for lithium and carbon, line bisector spans, convective blue-shifts (when feasible), and levels of magnetic activity from Hα, Hβ, and the Ca IIinfrared triplet. In this initial paper, we discuss our analysis tools and biases, presenting our first results from a pilot sub-sample of 54 stars (27 bona-fide dwarf stars observed with VATT+PEPSI and 27 bona-fide giant stars observed with STELLA+SES) and making all reduced spectra available to the community. We carried out a follow-up error analysis, including systematic biases and standard deviations based on a joint target sample for both facilities, as well as a comparison with external data sources.

Optical variability, rotation period, and inclination angle of the M9.5 dwarf BRI 0021−0214

ABSTRACT We report I-band photometric observations of the radio-detected M9.5 dwarf BRI 0021−0214, obtained with the Galway Ultra Fast Imager on the 1.8 m Vatican Advanced Technology Telescope (VATT) at Mt. Graham International Observatory, Arizona. In total, 19 h of observations over a 73 d baseline were obtained. BRI 0021−0214 was shown to exhibit modulated emission with a period of 3.052 ± 0.004 h with a mean amplitude variability of 0.0044 mag. When combined with rotational velocity data obtained from previous work, our newly discovered rotation period gives an inclination angle of 51.7$^{+5.0}_{-4.5}$ deg for the rotation axis of BRI 0021-0214 relative to our line of sight. Previous studies have reported that the most plausible cause for optical variability from this dwarf is a consequence of suspended co-rotating dust clouds in its atmosphere. However, reports of enhanced Hα and intermittent coherent radio emission suggest the possibility of auroral activity in its magnetosphere. Further, more coordinated multiwavlength observations of this dwarf could fully resolve the nature of this elusive rapid-rotator object’s observational properties.

Migratory Outbursting Quasi-Hilda Object 282P/(323137) 2003 BM80* * Based on observations obtained at the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council

We report that object 282P/(323137) 2003 BM80 is undergoing a sustained activity outburst, lasting over 15 months thus far. These findings stem in part from our NASA Partner Citizen Science project Active Asteroids (http://activeasteroids.net), which we introduce here. We acquired new observations of 282P via our observing campaign (Vatican Advanced Technology Telescope (VATT), Lowell Discovery Telescope (LDT), and the Gemini South telescope), confirming 282P was active on UT 2022 June 7, some 15 months after 2021 March images showed activity in the 2021–2022 epoch. We classify 282P as a member of the quasi-Hilda objects (QHOs), a group of dynamically unstable objects found in an orbital region similar to, but distinct in their dynamical characteristics to, the Hilda asteroids (objects in 3:2 resonance with Jupiter). Our dynamical simulations show 282P has undergone at least five close encounters with Jupiter and one with Saturn over the last 180 yr. 282P was most likely a Centaur or Jupiter-family comet (JFC) 250 yr ago. In 350 yr, following some 15 strong Jovian interactions, 282P will most likely migrate to become a JFC or, less likely, an outer main-belt asteroid orbit. These migrations highlight a dynamical pathway connecting Centaurs and JFCs with quasi-Hildas and, potentially, active asteroids. Synthesizing these results with our thermodynamical modeling and new activity observations, we find volatile sublimation is the primary activity mechanism. Observations of a quiescent 282P, which we anticipate will be possible in 2023, will help confirm our hypothesis by measuring a rotation period and ascertaining the spectral type.

Morphology and surface photometry of a sample of isolated early-type galaxies from deep imaging

Context. Isolated early-type galaxies are evolving in unusually poor environments for this morphological family, which is typical of cluster inhabitants. We investigate the mechanisms driving the evolution of these galaxies. Aims. Several studies indicate that interactions, accretions, and merging episodes leave their signature on the galaxy structure, from the nucleus down to the faint outskirts. We focus on revealing such signatures, if any, in a sample of isolated early-type galaxies, and we quantitatively revise their galaxy classification. Methods. We observed 20 (out of 104) isolated early-type galaxies, selected from the AMIGA catalog, with the 4KCCD camera at the Vatican Advanced Technology Telescope in the Sloan Digital Sky Survey g and r bands. These are the deepest observations of a sample of isolated early-type galaxies so far: on average, the light profiles reach μg ≈ 28.11 ± 0.70 mag arcsec−2 and μr ≈ 27.36 ± 0.68 mag arcsec−2. The analysis was performed using the AIDA package, providing point spread function-corrected 2D surface photometry up to the galaxy outskirts. The package provides a model of the 2D galaxy light distribution, which after model subtraction enhances the fine and peculiar structures in the residual image of the galaxies. Results. Our re-classification suggests that the sample is composed of bona fide early-type galaxies spanning from ellipticals to late-S0s galaxies. Most of the surface brightness profiles are best fitted with a bulge plus disc model, suggesting the presence of an underlying disc structure. The residuals obtained after the model subtraction show the nearly ubiquitous presence of fine structures, such as shells, stellar fans, rings, and tails. Shell systems are revealed in about 60% of these galaxies. Conclusions. Because interaction, accretion, and merging events are widely interpreted as the origin of the fans, ripples, shells and tails in galaxies, we suggest that most of these isolated early-type galaxies have experienced such events. Because they are isolated (after 2–3 Gyr), these galaxies are the cleanest environment in which to study phenomena connected with events like these.

Science of the Vatican Observatory since 2000

Five research areas have been the focus of the scientific work of the Specola Vaticana (Vatican Observatory) over the past twenty years: planetary sciences, stellar astronomy, extragalactic astronomy, cosmology, and the development of the Vatican Advanced Technology Telescope (vatt). The choice of research program is left to the individual astronomers, all of whom work closely with lay collaborators around the world. Notable, especially in connection with the vatt, is the close coordination of the Specola with the Steward Observatory of the University of Arizona. One unique strength of the Specola is its independence from short-term funding requirements. As a result of its stable funding, Specola astronomers can engage in long-term research programs such as surveys of meteorite properties, exoplanets, stellar clusters, and galaxy clusters, which may take ten or more years to come to fruition. In this way the Specola complements the large research programs of contemporary astronomy.

Carbon12C/13C isotope ratio ofαAurigae revised

Context. Capella (αAur) is one of the few binaries in the sky with two cool giant stars. With spectral types of G8III and G0III, the two components appear at different but distinct stages in their evolution. The G0 secondary star is a Hertzsprung-gap giant, and the G8 primary star is thought to be a clump giant.Aims. We present a new measure of the carbon12C/13C isotope ratio of the primary component of Capella using high-resolutionR ≈ 250 000 spectra obtained with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) with both the Vatican Advanced Technology Telescope (VATT) and the Large Binocular Telescope (LBT).Methods. Signal-to-noise ratios of up to 2 700 were obtained by averaging nightly spectra. These average spectra were used to disentangle the two binary components. The isotope ratio was derived with the use of spectrum synthesis from the CN lines at 8004 Å.Results. We found that the12C/13C ratio of the primary component of Capella is 17.8 ± 1.9. Our measurement precision is now primarily limited by the spectral-line data and by the grid-step size of the model atmospheres rather than the data. The separated spectrum of the secondary component does not show distinguishable12CN and13CN lines because of itsvsiniand higher temperature.Conclusions. Our new12C/13C value is significantly lower than the previous value of 27 ± 4 but now agrees better with the recent model prediction of 18.8–20.7.

The Extremely Luminous Quasar Survey in the Sloan Digital Sky Survey Footprint. II. The North Galactic Cap Sample

Abstract We present the North Galactic Cap sample of the Extremely Luminous Quasar Survey (ELQS-N), which targets quasars with M 1450 < −27 at 2.8 ≤ z < 5 in an area of ∼7600 deg2 of the Sloan Digital Sky Survey (SDSS) footprint with 90° < R.A. < 270°. Based on a near-infrared/infrared JKW2 color cut, the ELQS selection efficiently uses random forest methods to classify quasars and to estimate photometric redshifts; this scheme overcomes some of the difficulties of pure optical quasar selection at z ≈ 3. As a result, we retain a completeness of >70% over z ∼ 3.0–5.0 at m i ≲ 17.5, limited toward fainter magnitudes by the depth of the Two Micron All Sky Survey. The presented quasar catalog consists of a total of 270 objects, of which 39 are newly identified in this work with spectroscopy obtained at the Vatican Advanced Technology Telescope and the MMT 6.5 m telescope. In addition to the high completeness, which allowed us to discover new quasars in the already well-surveyed SDSS North Galactic Cap, the efficiency of our selection is relatively high at ∼79%. Using 120 objects of this quasar sample we are able to extend the previously measured optical quasar luminosity function (QLF) by one magnitude toward the bright end at 2.8 ≤ z ≤ 4.5. A first analysis of the QLF suggests a relatively steep bright-end slope of β ≈ −4 for this sample. This result contrasts with previous results in the same redshift range, which find a much flatter slope around β ∼ −2.5, but agrees with recent measurements of the bright-end slope at lower and higher redshifts. Our results constrain the bright-end slope at z = 2.8–4.5 to β < −2.94 with a 99% confidence.

TWO COLOR POPULATIONS OF KUIPER BELT AND CENTAUR OBJECTS AND THE SMALLER ORBITAL INCLINATIONS OF RED CENTAUR OBJECTS

ABSTRACT We present new optical colors for 28 Kuiper Belt objects (KBOs) and 35 Centaur objects measured with the 1.8 m Vatican Advanced Technology Telescope and the 4.3 m Discovery Channel Telescope. By combining these new colors with our previously published colors, we increase the sample size of our survey to 154 objects. Our survey is unique in that the uncertainties in our color measurements are less than half the uncertainties in the color measurements reported by other researchers in the literature. Small uncertainties are essential for discerning between a unimodal and a bimodal distribution of colors for these objects as well as detecting correlations between colors and orbital elements. From our survey, it appears red Centaurs have a broader color distribution than gray Centaurs. We find red Centaurs have a smaller orbital inclination angle distribution than gray Centaurs at the 99.3% confidence level. Furthermore, we find that our entire sample of KBOs and Centaurs exhibits bimodal colors at the confidence level. KBOs and Centaurs with H V > 7.0 have bimodal colors at the 99.96% confidence level and KBOs with H V < 6.0 have bimodal colors at the 96% confidence level.

CANNIBALIZATION AND REBIRTH IN THE NGC 5387 SYSTEM. I. THE STELLAR STREAM AND STAR-FORMING REGION

We have identified a low surface brightness stellar stream from visual inspection of SDSS imaging for the edge-on, spiral galaxy NGC5387. A blue overdensity was also identified in SDSS coincident with the stream intersection with the NGC5387 disk. The overdensity was also detected in the GALEX Deep Imaging Survey and found to contribute 38% of the total FUV integrated flux from NGC5387, which suggests that the region is actively forming stars. Deeper imaging was acquired with the Vatican Advanced Technology Telescope (VATT) in the B, V, and R filters that confirmed the presence of both the stellar stream and the blue overdensity. Analysis of the VATT photometry indicates the stellar stream is red in color, B-V = 0.7, and has a stellar mass of 6x10^8 M$_{\odot}$, which implies a merger ratio of 1:50. Assessment of the stream morphology suggests that the merger event has a circular radius, R~16 kpc, the stream formed in ~400 Myr, and the progenitor had a total mass of ~2x10 M$_{\odot}$. Spectroscopy from LBT+MODS1 was used to determine that the blue overdensity is at the same redshift as NGC5387, consists of young stellar populations (~10 Myr), is metal-poor (12 + log(O/H) = 8.03), and forming stars at an enhanced rate (~1-3 M$_{\odot}$/year) given its total stellar mass (2x10^7 M$_{\odot}$). Several interpretations are posited to explain these observational data, of which the most likely are (i) that the blue overdensity is a region of enhanced star formation in the outer disk of NGC5387 induced by the minor accretion event, and (ii) that the blue overdensity is the progenitor of the stellar stream undergoing a period of enhanced star formation as a result of its interaction with NGC5387. Confirmation and theoretical exploration of these scenarios are presented in a companion paper.

Polar ring galaxies in the Galaxy Zoo

We report observations of 16 candidate polar ring galaxies (PRGs) identified by the Galaxy Zoo project in the Sloan Digital Sky Survey (SDSS) database. Deep images of five galaxies are available in the SDSS Stripe82 database, while to reach similar depth we observed the remaining galaxies with the 1.8-m Vatican Advanced Technology Telescope. We derive integrated magnitudes and u-r colours for the host and ring components and show continuum-subtracted H\alpha+[NII] images for seven objects. We present a basic morphological and environmental analysis of the galaxies and discuss their properties in comparison with other types of early-type galaxies. Follow-up photometric and spectroscopic observations will allow a kinematic confirmation of the nature of these systems and a more detailed analysis of their stellar populations.

Vilnius Multicolor CCD Photometry of the Open Cluster NGC 752

AbstractWe have performed multicolor CCD observations of the central area of NGC 752 to search for faint, low-mass members of this open cluster. Four 12’ x 12’ fields were taken on the 1.8 m Vatican Advanced Technology Telescope (Mt. Graham, Arizona) using a 4K CCD camera and eight intermediate-band filters of the Strömvil (Strömgren + Vilnius) system. In this paper we present a catalog of photometry for 405 stars down to the limiting magnitude V = 18.5, which contains V magnitudes and color indices of the Vilnius system, together with photometric determinations of spectral types, absolute magnitudes M

LIFTING THE VEIL OF DUST FROM NGC 0959: THE IMPORTANCE OF A PIXEL-BASED TWO-DIMENSIONAL EXTINCTION CORRECTION

We present the results of a study of the late-type spiral galaxy NGC 0959, before and after application of the pixel-based dust extinction correction described in Tamura et al. 2009 (Paper I). Galaxy Evolution Explorer (GALEX) far-UV (FUV) and near-UV (NUV), ground-based Vatican Advanced Technology Telescope (VATT) UBVR, and Spitzer/Infrared Array Camera (IRAC) 3.6, 4.5, 5.8, and 8.0 micron images are studied through pixel Color-Magnitude Diagrams (pCMDs) and pixel Color-Color Diagrams (pCCDs). We define groups of pixels based on their distribution in a pCCD of (B - 3.6 micron) versus (FUV - U) colors after extinction correction. In the same pCCD, we trace their locations before the extinction correction was applied. This shows that selecting pixel groups is not meaningful when using colors uncorrected for dust. We also trace the distribution of the pixel groups on a pixel coordinate map of the galaxy. We find that the pixel-based (two-dimensional) extinction correction is crucial to reveal the spatial variations in the dominant stellar population, averaged over each resolution element. Different types and mixtures of stellar populations, and galaxy structures such as a previously unrecognized bar, become readily discernible in the extinction-corrected pCCD and as coherent spatial structures in the pixel coordinate map.

MAPPING THE SPATIAL DISTRIBUTION OF DUST EXTINCTION IN NGC 959 USING BROADBAND VISIBLE AND MID-INFRARED FILTERS

We present a method to estimate and map the two-dimensional distribution of dust extinction in the late-type spiral galaxy NGC 959 from the theoretical and observed flux ratio of optical V and mid-IR (MIR) 3.6 micron images. Our method is applicable to both young and old stellar populations for a range of metallicities, and is not restricted to lines-of-sight toward star-formation (SF) regions. We explore this method using a pixel-based analysis on images of NGC 959 obtained in the V-band at the Vatican Advanced Technology Telescope (VATT) and at 3.6 micron (L-band) with Spitzer/IRAC. We present the original and extinction corrected GALEX far-UV (FUV) and near-UV (NUV) images, as well as optical UBVR images of NGC 959. While the dust lanes are not clearly evident at GALEX resolution, our dust map clearly traces the dust that can be seen silhouetted against the galaxy's disk in the high-resolution HST images of NGC 959. The advantages of our method are: (1) it only depends on two relatively common broadband images in the optical V-band and in the MIR at 3.6 micron (but adding a near-UV band improves its fidelity); and (2) it is able to map the two-dimensional spatial distribution of dust within a galaxy. This powerful tool could be used to measure the detailed distribution of dust extinction within higher redshift galaxies to be observed with, e.g., the HST/WFC3 (optical--near-IR) and JWST (mid-IR), and to distinguish properties of dust within galaxy bulges, spiral arms, and inter-arm regions.

Multicolor CCD photometry of the open cluster NGC 752

AbstractWe obtained CCD observations of the open cluster NGC 752 with the 1.8m Vatican Advanced Technology Telescope (Mt. Graham, Arizona) with a 4K CCD camera and eight intermediate-band filters of the Stromvil (Strömgren + Vilnius) system. Four 12′ × 12′ fields were observed, covering the central part of the cluster. The good-quality multicolor data made it possible to obtain precise estimates of distance moduli, metallicity and foreground reddening for individual stars down to the limiting magnitude, V = 17.5, enabling photometric identification of faint cluster members. The new observations provide an extension of the lower main sequence to three magnitudes beyond the previous (photographic) limit. A relatively small number of photometric members identified at fainter magnitudes seems to be indicative of actual dissolution of the cluster from the low-mass end.

The Large-Grained Dust Coma of 174P/Echeclus

ABSTRACTOn 2005 December 30, Y.-J. Choi and P. R. Weissman discovered that the formerly dormant Centaur 2000 EC98 was in strong outburst. Previous observations by P. Rousselot et al. spanning a 3-year period indicated a lack of coma down to the 27 mag arcsec-2 level. We present Spitzer Space Telescope MIPS observations of this newly active Centaur—now known as 174P/Echeclus (2000 EC98)—or 60558 Echeclus—taken in 2006 late February. The images show strong signal at both the 24 and 70 μm bands and reveal an extended coma about 2′ in diameter. Analyses yield estimates of the coma signal contribution that are in excess of 90% of the total signal in the 24 μm band. Dust production estimates ranging from 1.7–4 × 102 kg s-1 are on the order of 30 times that seen in other Centaurs. Simultaneous visible-wavelength observations were also obtained with Palomar Observatory's 200-inch telescope, the 1.8-m Vatican Advanced Technology Telescope, the Bohyunsan Optical Astronomy Observatory (BOAO) 1.8-m telescope, and Table Mountain Observatory's 0.6-m telescope, revealing a coma morphology nearly identical to the mid-IR observations. The grain size distribution derived from the data yields a log particle mass power-law with slope parameter α = -0.87 ± 0.07, and is consistent with steady cometary activity, such as that observed during the Stardust spacecraft’s encounter at 81P/Wild 2, and not with an impact-driven event, such as that caused by the Deep Impact experiment.

A G-SCIDAR for Ground-Layer Turbulence Measurements at High Vertical Resolution

ABSTRACT We propose a new method based on the generalized SCIDAR principle to characterize the vertical distribution of the turbulence in the first few hundred meters above the telescope with a better vertical resolution than usually achievable by such an instrument. Using a wide binary star (35″ separation) and analyzing the spatio-temporal cross-correlation images, we achieve a profile with a vertical resolution of a few tens of meters. We present the principle and the data-reduction process of this method and show first results obtained with a SCIDAR instrument mounted to the Vatican Advanced Technology Telescope (VATT) on the top of Mount Graham. As an application, we estimate the fraction of the turbulence between the dome of the VATT and the primary mirror of the Large Binocular Telescope.

Generalized SCIDAR Measurements at Mount Graham

ABSTRACTWe present the results of optical turbulence measurements conducted with a Generalized SCIDAR (scintillation detection and ranging) at Mount Graham during 16 nights in 2004 and 2005 at the Vatican Advanced Technology Telescope. The principle of the data reduction process is shown, as is the validation of the obtained results. From the measured C2N and wind speed profiles, the astroclimatic parameters, such as seeing ϵ0, isoplanatic angle ϑ0, wave‐front coherence time τ0, and isopistonic angle ϑP, are calculated, and their seasonal variation is studied. With subtraction of the dome seeing, we obtained median values for ϵ0 (0.67″), ϑ0 (2.7″), τ0 (3.6 ms), and ϑP (3.3″) that indicate that the astronomical seeing at Mount Graham is comparable to the best sites in the world. The seasonal variation of the vertical structure of the C2N profiles is studied, and the contribution by the ground‐layer turbulence is analyzed. Furthermore, typical discretized C2N profiles that are suitable for numerical simulations are determined.

Near-infrared spectra of the leading and trailing hemispheres of Enceladus

We present individual spectra 0.8–2.5 μm of the leading and trailing hemispheres of Enceladus obtained with the CorMASS spectrograph on the 1.8 m Vatican Advanced Technology Telescope (VATT) at the Mount Graham International Observatory. While the absorption bands of water ice dominate the spectrum of both hemispheres, most of these bands are stronger on the leading hemisphere than the trailing hemisphere. In addition, longward of 1 μm, the continuum slope is greater on the leading hemisphere than the trailing hemisphere. These differences could be produced by the presence of particles on the trailing side that are smaller and/or microstructurally more complex than those on the leading side, consistent with the preferential erosion or structural degradation of regolith particle grains on the trailing side by magnetospheric sweeping. We also explore compositional differences between the two hemispheres by applying Hapke spectrophotometric mixture models to the spectra whose components include water ice and ammonia hydrate (1% NH 3⋅H 2O). We find that spectral models which include as much as 25% by weight ammonia hydrate intimately mixed with water ice and covering 80% of the illuminated area of the satellite fit the observed spectrum of both the leading and trailing hemispheres. Areal (checkerboard) mixing models of ammonia hydrate and water ice fit the leading hemisphere with 15% of the surface comprised of ammonia hydrate and the trailing hemisphere with 10% ammonia hydrate. Therefore, while these spectral data do not contain an unambiguous detection of ammonia hydrate on Enceladus, our spectral models do not preclude the presence of a modest amount of 1% NH 3⋅H 2O on both hemispheres. We examine spectral differences and similarities between both hemispheres and the tenuous E ring within which Enceladus orbits. The spectral resolution ( R = λ / Δ λ ) of these CorMASS data ( R ∼ 300 ) is comparable to but nevertheless higher than that of the Visual-Infrared Mapping Spectrometer (VIMS) ( R = 225 ) onboard the Cassini spacecraft.

UBVRandHubble Space TelescopeMid‐Ultraviolet and Near‐Infrared Surface Photometry and Radial Color Gradients of Late‐Type, Irregular, and Peculiar Galaxies

We introduce a data set of 142 mostly late-type spiral, irregular, and peculiar (interacting or merging) nearby galaxies observed in UBVR at the Vatican Advanced Technology Telescope (VATT), and we present an analysis of their radial color gradients. We confirm that nearby elliptical and early- to mid-type spiral galaxies show either no or only small color gradients, becoming slightly bluer with radius. In contrast, we find that late-type spiral, irregular, peculiar, and merging galaxies become on average redder with increasing distance from the center. The scatter in radial color gradient trends increases toward later Hubble type. As a preliminary analysis of a larger data set obtained with the Hubble Space Telescope (HST), we also analyze the color gradients of six nearby galaxies observed with NICMOS in the near-IR (H) and with WFPC2 in the mid-UV (F300W) and red (F814W). We discuss the possible implications of these results on galaxy formation and compare our nearby galaxy color gradients to those at high redshift. We present examples of images and UBVR radial surface brightness and color profiles, as well as of the tables of measurements; the full atlas and tables are published in the electronic edition only.