Deep Near-infrared Imaging Research Articles

Photometric properties of six Local Volume dwarf galaxies from deep near-infrared observations

We have obtained deep near-infrared (NIR) J- (1.25 μm), H- (1.65 μm) and Ks-band (2.15 μm) imaging for a sample of six dwarf galaxies (MB≳−17 mag) in the Local Volume (LV; D≲ 10 Mpc). The sample consists mainly of early-type dwarf galaxies found in various environments in the LV. Two galaxies (LEDA 166099 and UGCA 200) in the sample are detected in the NIR for the first time. The deep NIR images allow for a detailed study of the photometric and structural properties of each galaxy. The surface brightness (SB) profiles of the galaxies are detected down to the ∼ 24 mag arcsec−2 isophote in the J and H bands, and 23 mag arcsec−2 in the Ks band. The total magnitudes of the galaxies are derived in the three wavelength bands. For the brightest galaxies (MB≲− 15.5 mag) in the sample, we find that the Two-Micron All-Sky Survey underestimates the total magnitudes of these systems by up to ≲0.5 mag. The radial SB profiles of the galaxies are fitted with an exponential (for those galaxies having a stellar disc) or Sérsic law to derive the structure of the underlying stellar component. In particular, the effective SB (μe) and effective radius (re) are determined from the analytic fits to the SB profile. The J−Ks colours for the galaxies have been measured to explore the luminosity–metallicity relation for early-type dwarfs. In addition, the B−Ks colours of the galaxies are used to assess their evolutionary state relative to other galaxy morphologies. The total stellar masses of the dwarf galaxies are derived from the H-band photometric measurements. These will later be compared to the dynamical mass estimates for the galaxies to determine their dark matter content.

Deep near-infrared imaging of the HE0450-2958 system

<i>Context. <i/>The QSO HE0450-2958 and the companion galaxy with which it is interacting, both ultra luminous in the infrared, have been the subject of much attention in recent years, as the quasar host galaxy remained undetected. This led to various interpretations on QSO and galaxy formation and co-evolution, such as black hole ejection, jet induced star formation, dust obscured galaxy, or normal host below the detection limit. <i>Aims. <i/> We carried out deep observations in the near-IR in order to solve the puzzle concerning the existence of any host.<i>Methods. <i/> The object was observed with the ESO VLT and HAWK-I in the near-IR <i>J<i/>-band for 8 h. The images have been processed with the MCS deconvolution method, permitting accurate subtraction of the QSO light from the observations.<i>Results. <i/>The compact emission region situated close to the QSO, called the blob, which previously showed only gas emission lines in the optical spectra, is now detected in our near-IR images. Its high brightness implies that stars likely contribute to the near-IR emission. The blob might thus be interpreted as an off-centre, bright and very compact host galaxy, involved in a violent collision with its companion.

DEEPKs-NEAR-INFRARED SURFACE PHOTOMETRY OF 80 DWARF IRREGULAR GALAXIES IN THE LOCAL VOLUME

We present deep near-infrared (K_s) images and surface photometry for 80 dwarf irregular galaxies (dIs) within ~5 Mpc of the Milky Way. The galaxy images were obtained at five different facilities between 2004 and 2006. The image reductions and surface photometry have been performed using methods specifically designed for isolating faint galaxies from the high and varying near-infrared sky level. Fifty-four of the 80 dIs have surface brightness profiles which could be fit to a hyperbolic-secant (sech) function, while the remaining profiles could be fit to the sum of a sech and a Gaussian function. From these fits, we have measured central surface brightnesses, scale lengths, and integrated magnitudes. This survey is part of a larger study of the connection between large-scale structure and the global properties of dIs, the hypothesized building-blocks of more massive galaxies.

DISCOVERY OF FOUR kpc-SCALE BINARY ACTIVE GALACTIC NUCLEI

We report the discovery of four kpc-scale binary AGNs. These objects were originally selected from the Sloan Digital Sky Survey based on double-peaked [O III] 4959,5007 emission lines in their fiber spectra. The double peaks could result from pairing active supermassive black holes (SMBHs) in a galaxy merger, or could be due to bulk motions of narrow-line region gas around a single SMBH. Deep near-infrared (NIR) images and optical slit spectra obtained from the Magellan 6.5 m and the APO 3.5 m telescopes strongly support the binary SMBH scenario for the four objects. In each system, the NIR images reveal tidal features and double stellar components with a projected separation of several kpc, while optical slit spectra show two Seyfert 2 nuclei spatially coincident with the stellar components, with line-of-sight velocity offsets of a few hundred km/s. These objects were drawn from a sample of only 43 objects, demonstrating the efficiency of this technique to find kpc-scale binary AGNs.

ON A NEW NEAR-INFRARED METHOD TO ESTIMATE THE ABSOLUTE AGES OF STAR CLUSTERS: NGC 3201 AS A FIRST TEST CASE

We present a new method to estimate the absolute ages of stellar systems. This method is based on the difference in magnitude between the main sequence turn-off (MSTO) and a well defined knee located along the lower main sequence (MSK). This feature is caused by the collisionally induced absorption of molecular hydrogen and it can be easily identified in near-infrared (NIR) and in optical-NIR color-magnitude diagrams of stellar systems. We took advantage of deep and accurate NIR images collected with the Multi-Conjugate Adaptive Optics Demonstrator temporarily available on the Very Large Telescope and of optical images collected with the Advanced Camera for Surveys Wide Field Camera on the Hubble Space Telescope and with ground-based telescopes to estimate the absolute age of the globular NGC3201 using both the MSTO and the Delta(MSTO-MSK). We have adopted a new set of cluster isochrones and we found that the absolute ages based on the two methods agree to within one sigma. However, the errors of the ages based on the Delta(MSTO-MSK) method are potentially more than a factor of two smaller, since they are not affected by uncertainties in cluster distance or reddening.Current isochrones appear to predict slightly bluer (~0.05mag) NIR and optical-NIR colors than observed for magnitudes fainter than the MSK.

THE LIFETIME OF PROTOPLANETARY DISKS IN A LOW-METALLICITY ENVIRONMENT

The extreme outer Galaxy (EOG), the region with a Galactic radius of more than 18 kpc, is known to have very low metallicity, about one-tenth that of the solar neighborhood. We obtained deep near-infrared (NIR) images of two very young ($\sim$0.5 Myr) star-forming clusters that are one of the most distant embedded clusters in the EOG. We find that in both clusters the fraction of stars with NIR excess, which originates from the circumstellar dust disk at radii of $\leq$0.1 AU, is significantly lower than those in the solar neighborhood. Our results suggest that most stars forming in the low-metallicity environment experience disk dispersal at an earlier stage ($<$1 Myr) than those forming in the solar metallicity environment (as much as $\sim$5--6 Myr). Such rapid disk dispersal may make the formation of planets difficult, and the shorter disk lifetime with lower metallicity could contribute to the strong metallicity dependence of the well-known "planet-metallicity correlation", which states the probability of a star hosting a planet increases steeply with stellar metallicity. The reason for the rapid disk dispersal could be increase of the mass accretion rate and/or the effective far-ultraviolet photoevaporation due to the low extinction; however, another unknown mechanism for the EOG environment could be contributing significantly.

HOST GALAXIES OFz= 4 QUASARS, ,

We have undertaken a project to investigate the host galaxies and environments of a sample of quasars at z~4. In this paper, we describe deep near-infrared imaging of 34 targets using the Magellan I and Gemini North telescopes. We discuss in detail special challenges of distortion and nonlinearity that must be addressed when performing PSF subtraction with data from these telescopes and their IR cameras, especially in very good seeing. We derive black hole masses from emission-line spectroscopy, and we calculate accretion rates from our K_s-band photometry, which directly samples the rest-frame B for these objects. We introduce a new isophotal diameter technique for estimating host galaxy luminosities. We report the detection of four host galaxies on our deepest, sharpest images, and present upper limits for the others. We find that if host galaxies passively evolve such that they brighten by 2 magnitudes or more in the rest-frame B band between the present and z=4, then high-z hosts are less massive at a given black hole mass than are their low-z counterparts. We argue that the most massive hosts plateau at <~10L*. We estimate the importance of selection effects on this survey and the subsequent limitations of our conclusions. These results are in broad agreement with recent semi-analytical models for the formation of luminous quasars and their host spheroids by mergers of gas-rich galaxies, with significant dissipation, and self-regulation of black hole growth and star-formation by the burst of merger-induced quasar activity.

MOIRCS DEEP SURVEY. IV. EVOLUTION OF GALAXY STELLAR MASS FUNCTION BACK TOz∼ 3

We use very deep near-infrared (NIR) imaging data obtained in MOIRCS Deep Survey (MODS) to investigate the evolution of the galaxy stellar mass function back to z~3. The MODS data reach J=24.2, H=23.1, K=23.1 (5sigma, Vega magnitude) over 103 arcmin^2 (wide) and J=25.1, H=23.7, K=24.1 over 28 arcmin^2 (deep) in the GOODS-North region. The wide and very deep NIR data allow us to measure the number density of galaxies down to low stellar mass (10^9-10^10 Msun) even at high redshift with high statistical accuracy. The normalization of the mass function decreases with redshift and the integrated stellar mass density becomes ~ 8-18% of the local value at z~2 and ~ 4-9% at z~3, which are consistent with results of previous studies in general fields. Furthermore, we found that the low-mass slope becomes steeper with redshift from alpha ~- 1.3 at z~1 to alpha ~- 1.6 at z~3, and that the evolution of the number density of low-mass (10^9-10^10 Msun) galaxies is weaker than that of M* (~10^11 Msun) galaxies. This indicates that the contribution of low-mass galaxies to the total stellar mass density has been significant at high redshift. The steepening of the low-mass slope with redshift is opposite trend expected from the stellar mass dependence of the specific star formation rate reported in previous studies. The present result suggests that the hierarchical merging process overwhelmed the effect of the stellar mass growth by star formation and was very important for the stellar mass assembly of these galaxies at 1<~z<~3.

MOIRCS DEEP SURVEY. III. ACTIVE GALACTIC NUCLEI IN MASSIVE GALAXIES ATz= 2-4

We investigate the X-ray properties of the K-band-selected galaxies at redshift 2 < z < 4 by using our deep near-infrared images obtained in the MOIRCS Deep Survey project and the published Chandra X-ray source catalog. 61 X-ray sources with the 2-10 keV luminosity L_X = 10^{42}-10^{44} erg/s are identified with the K-selected galaxies and we found that they are exclusively (90%) associated with the massive objects with stellar mass larger than 10^{10.5} Msun. Our results are consistent with the idea that the M_BH/M_str ratio of the galaxies at z=2-4 is similar to the present-day value. On the other hand, the AGN detection rate among the very massive galaxies with the stellar mass larger than 10^{11} Msun is high, 33% (26/78). They are active objects in the sense that the black-hole mass accretion rate is ~ 1-50% of the Eddington limit if they indeed have similar M_BH/M_str ratio with those observed in the local universe. The active duration in the AGN duty cycle of the high-redshift massive galaxies seems large.

NTT follow-up observations of star cluster candidates from the FSR catalogue

We are conducting a large program to classify newly discovered Milky Way star cluster candidates from the list of Froebrich et al. Here, we present deep near-infrared (NIR) follow-up observations from European Southern Observatory–New Technology Telescope (ESO/NTT) of 14 star cluster candidates. We show that the combined analysis of star density maps (SDMs) and colour–colour/magnitude diagrams derived from deep NIR imaging is a viable tool to reliably classify new stellar clusters. This allowed us to identify two young clusters with massive stars, three intermediate age open clusters and two globular cluster candidates among our targets. The remaining seven objects are unlikely to be stellar clusters. Among them is the object FSR 1767 which has previously been identified as a globular cluster using Two-Micron All-Sky Survey (2MASS) data by Bonatto et al. Our new analysis shows that FSR 1767 is not a star cluster. We also summarize the currently available follow-up analysis of the FSR candidates and conclude that this catalogue may contain a large number of new stellar clusters, probably dominated by old open clusters.

A Confirmation of the Strong Clustering of Distant Red Galaxies at 2 &lt; z &lt; 3

Recent studies have shown that distant red galaxies (DRGs), which dominate the high-mass end of the galaxy population at z~2.5, are more strongly clustered than the population of blue star-forming galaxies at similar redshifts. However these studies have been severely hampered by the small sizes of fields having deep near-infrared imaging. Here we use the large UKIDSS Ultra Deep Survey to study the clustering of DRGs. The size and depth of this survey allows for an unprecedented measurement of the angular clustering of DRGs at 2<z_phot<3 and K<21. The correlation function shows the expected power law behavior, but with an apparent upturn at theta<~10. We deproject the angular clustering to infer the spatial correlation length, finding 10.6+-1.6 h^-1 Mpc. We use the halo occupation distribution framework to demonstrate that the observed strong clustering of DRGs is not consistent with standard models of galaxy clustering, confirming previous suggestions that were based on smaller samples. Inaccurate photometric redshifts could artificially enhance the observed clustering, however significant systematic redshift errors would be required to bring the measurements into agreement with the models. Another possibility is that the underlying assumption that galaxies interact with their large-scale environment only through halo mass is not valid, and that other factors drive the evolution of the oldest, most massive galaxies at z~2.

A pilot survey for KX QSOs in the UKIDSS Ultra Deep Survey Field

We have undertaken a pilot survey for faint quasi-stellar objects (QSOs) in the UKIRT Infrared Deep Survey (UKIDSS) Ultra Deep Survey (UDS) Field using the KX selection technique. These observations exploit the very deep near-infrared and optical imaging of this field from United Kingdom Infrared Telescope (UKIRT) and Subaru to select candidate QSOs based on their VJK colours and morphologies. We determined redshifts for 426 candidates using the AAOmega spectrograph on the Anglo-Australian Telescope in service time. We identify 17 QSOs (M B ≤ -23) in this pilot survey at z = 1.57-3.29. We combine our sample with an X-ray-selected sample of QSOs in the same field (a large fraction of which also comply with our KX selection) to constrain the surface density of QSOs with K ≤ 20, deriving limits on the likely surface density of 85-150 deg -2 . We use the good image quality available from our near-infrared imaging to detect a spatially extended component of the QSO light which probably represents the host galaxies. We also use our sample to investigate routes to improve the selection of KX QSOs at faint limits in the face of the significant contamination by compact, foreground galaxies. The brightest examples from our combined QSO sample will be used in conjunction with a large Very Large Telescope VIMOS spectroscopic survey of high-redshift galaxies in this region to study the structures inhabited by gas, galaxies and growing supermassive black holes at high redshifts in the UKIDSS UDS.

Subaru/MOIRCS Near-Infrared Imaging in the Proto-Cluster Region at z = 3.1

Abstract We present the results of deep near-infrared imaging observations of the $z=3.1$ proto-cluster region in the SSA 22a field taken by MOIRCS mounted on the Subaru Telescope. We observed a 21.7 arcmin$^2$ field to depths of $J=$ 24.5, $H=$ 24.3, and $K=$ 23.9 (5$\sigma$). We examined the distribution of the $K$-selected galaxies at $z \sim 3$ by using a simple color cut for distant red galaxies (DRGs) as well as a photometric-redshift selection technique. The marginal density excess of DRGs and the photo-$z$ selected objects were found around the two most luminous Ly$\alpha$ blobs (LABs). We investigated the correlation between the $K$-selected objects and the LABs, and found that several galaxies with stellar mass, $M_* = 10^{9}$–$10^{11} M_\odot$, exist in the vicinity of LABs, especially around the two most luminous ones. We also found that 7 of the 8LABs in the field have plausible $K_{\rm s}$-band counterparts, and the sum of the stellar mass possibly associated with LABs correlates with their luminosity and surface brightness, which implies that the origin of Ly$\alpha$ emission may be closely correlated with their previous star-formation phenomena.

LUMINOSITY AND MASS FUNCTIONS AT THE VERY LOW MASS SIDE IN NGC 1333

We present the results of a deep near-infrared (NIR) imaging survey searching for very low mass young stellar objects (YSOs) in the embedded cluster associated with the Perseus molecular cloud. Our observations cover an area of ~5'× 5' in the NGC 1333-S region at J-, H-, and Ks-bands. The 10σ limiting magnitudes exceed 18 mag in all three bands. Based on NIR color-color diagrams, embedded YSO candidates were identified using NIR excesses. The derived frequency of these YSO candidates with NIR excess emission among all the detected sources is 58+10 –13%. The higher frequency of YSOs with NIR excesses implies that NGC 1333 is an active and young star-forming region. Approximately half of the YSO candidates exhibit extremely low luminosity, indicating very low mass. Combining the reddening-corrected luminosity with theoretical evolutionary models, the low-luminosity YSO candidates are considered to be young substellar-mass objects. Furthermore, some sources could have planetary masses. In addition, we carried out CO molecular-line observations of the same cloud region. The results suggested that the YSO candidates are likely formed on the side of the parent molecular cloud and star-formation activity could be high. The K-band luminosity function of all the detected sources revealed a significant population of extremely low-luminosity sources in NGC 1333. The reddening-corrected J-band luminosity function of the YSO candidates does not clearly decline to the completeness limit and seems to be bimodal. We also argue that the fraction of substellar objects is larger than those in other young clusters and the mass function of the YSO candidates appears to be increasing toward the substellar-mass regime, similar to that of dust clumps. It implies that substellar-mass distributions may depend on the initial conditions of the molecular cloud.

The young Galactic star cluster [DBS2003] 179

Recent near- and mid-infrared surveys have brought evidence that the Milky Way continues to form massive clusters. We carry out a program to determine the basic physical properties of the new massive cluster candidate [DBS2003]179. Medium-resolution K-band spectra and deep near-infrared images of [DBS2003]179 were used to derive the spectral types of eight member stars, and to estimate the distance and reddening to the cluster. Seven of ten stars with spectra show emission lines. Comparison with template spectra indicated that they are early O-type stars. The mean radial velocity of the cluster is Vrad=-77+-6 km/s. Knowing the spectral types of the members and the color excesses, we determined extinction Av~16.6 and distance modulus (m-M)0~14.5 mag (D~7.9 kpc). The presence of early O-stars and a lack of red supergiants suggests a cluster age of 2-5Myr. The total cluster mass is approximated to 0.7x10^4 Msun and it is not yet dynamically relaxed. The candidate [DBS2003]179 further increases the family of the massive young clusters in the Galaxy, although it appears less massive than the prototypical starburst clusters.

The Nascent Red Sequence at \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $z\sim 2$ \end{document}

We present new constraints on the evolution of the early-type galaxy color-magnitude relation (CMR) based on deep near-infrared imaging of a galaxy protocluster at z = 2.16 obtained using NICMOS on board the Hubble Space Telescope. This field contains a spectroscopically confirmed space overdensity of Lyα- and Hα-emitting galaxies that surrounds the powerful radio galaxy MRC 1138–262. Using these NICMOS data we identify a significant surface overdensity (=6.2 times) of red J110 − H160 galaxies in the color-magnitude diagram (when compared with deep NICMOS imaging from the HDF-N and UDF). The optical-NIR colors of these prospective red-sequence galaxies indicate the presence of ongoing dust-obscured star formation or recently formed (≲1.5 Gyr) stellar populations in a majority of the red galaxies. We measure the slope and intrinsic scatter of the CMR for three different red galaxy samples selected by a wide color cut and using photometric redshifts both with and without restrictions on rest-frame optical morphology. In all three cases both the rest-frame U − B slope and intrinsic color scatter are considerably higher than corresponding values for lower redshift galaxy clusters. These results suggest that while some relatively quiescent galaxies do exist in this protocluster both the majority of the galaxy population and hence the color-magnitude relation are still in the process of forming, as expected.

Star Formation in the Extreme Outer Galaxy: Digel Cloud 2 Clusters

We obtained deep near-infrared (NIR) images of two embedded clusters at the northern and southern CO peaks of Cloud 2, which is one of the most distant star-forming regions in the extreme outer Galaxy, at the Galactic radius (Rg) of ~19 kpc. We detected cluster members with a mass detection limit of <0.1 M☉, which is well into the substellar regime (K ~ 21 mag, 5 σ). These high-quality data enable a comparison of EOG values to those in the solar neighborhood on the same basis for the first time. We first constructed the NIR color-color diagram in the Mauna Kea Observatory (MKO) filter system and also for the low-metallicity environment, since the metallicity in the EOG is much lower than it is in the solar neighborhood. The estimated stellar density suggests that isolated-type star formation is ongoing in Cloud 2-N, while cluster-type star formation is ongoing in Cloud 2-S. Despite this different star formation mode, other characteristics of the two clusters are almost identical: (1) the K-band luminosity functions (KLFs) of the two clusters are quite similar, as are the estimated IMFs and ages (~0.5-1 Myr) from the KLF fitting; (2) the estimated star formation efficiencies (SFEs) for both clusters are typical compared to those of embedded clusters in the solar neighborhood. The similarity of two independent clusters with a large separation (~25 pc) strongly suggests that their star formation activities were triggered by the same mechanism, probably a supernova remnant (GSH 138-01-94), as suggested in our earlier works.

A FLAMINGOS Deep Near‐Infrared Imaging Survey of the Rosette Complex. I. Identification and Distribution of the Embedded Population

We present the results of a deep near-infrared imaging survey of the Rosette Complex. We studied the distribution of young embedded sources using a variation of the Nearest Neighbor Method applied to a carefully selected sample of near-infrared excess (NIRX) stars which trace the latest episode of star formation in the complex. Our analysis confirmed the existence of seven clusters previously detected in the molecular cloud, and identified four more clusters across the complex. We determined that 60% of the young stars in the complex and 86% of the stars within the molecular cloud are contained in clusters, implying that the majority of stars in the Rosette formed in embedded clusters. We compare the sizes, infrared excess fractions and average extinction towards individual clusters to investigate their early evolution and expansion. We found that the average infrared excess fraction of clusters increases as a function of distance from NGC 2244, implying a temporal sequence of star formation across the complex. This sequence appears to be primordial, possibly resulting from the formation and evolution of the molecular cloud and not from the interaction with the HII region.

Faint arc-minute extended radio emission around Cygnus X-3

Aims. We revisit the vicinity of the microquasar Cygnus X-3 at radio wavelengths. We aim to improve our previous search for possible associated extended radio features/hot spots in the position angle of the Cygnus X-3 relativistic jets focusing on shorter angular scales than previously explored. Methods. Our work is mostly based on analyzing modern survey and archive radio data, mainly including observations carried out with the Very Large Array and the Ryle Telescopes. We also used deep near-infrared images that we obtained in 2005. Results. We present new radio maps of the Cygnus X-3 field computed after combining multi-configuration Very Large Array archive data at 6 cm and different observing runs at 2 cm with the Ryle Telescope. These are probably among the deepest radio images of Cygnus X-3 reported to date at cm wavelengths. Both interferometers reveal an extended radio feature within a few arc-minutes of the microquasar position, thus making our detection more credible. Moreover, this extended emission is possibly non-thermal, although this point still needs confirmation. Its physical connection with the microquasar is tentatively considered under different physical scenarios. We also report on the serendipitous discovery of a likely Fanaroff-Riley type II radio galaxy only $3^{\prime}$ away from Cygnus X-3.

Deep near-infrared photometry of the globular cluster 47 Tucanae. Reconciling theory and observations

Context. The Galactic globular cluster 47 Tucanae is central to studies of Galaxy formation, and a test-bed for theoretical models, distance determination and extragalactic age-dating techniques. Independent parallax-based distance determinations in the optical spectral range provide discrepant results; also, star counts along the Red Giant Branch from optical data have disclosed a worrying disagreement with theoretical predictions, that impacts not only the theory of red giant stars, but also the calibration of the age scale of extragalactic systems. Aims. Our new near-infrared data for 47 Tuc set constraints on its distance and test the reliability of theoretical red giant branch star counts, independently of previous conclusions from optical work. Methods. We have obtained deep near-infrared imaging of 47 Tuc using SOFI at the ESO New Technology Telescope. Colour−magnitude diagrams, isochrones and synthetic horizontal branch modelling have been used to determine the distance of 47 Tuc and constrain its age. We have also constructed a luminosity function of red giant stars, which has been compared with theoretical predictions of stellar evolution models. Results. We obtain a distance (m − M)0 = 13.18 ± 0.03 (random) ± 0.04 (systematic), for [Fe/H] = −0.7 ± 0. 1a ndE(B − V) = 0.04±0.02. This supports the shorter end of the range of distances obtained from optical studies. The mean horizontal branch star mass is between 0.65 and 0.66 M� , and its 1σ Gaussian dispersion is between 0.010 and 0.012 M� . The cluster age can only be approximately estimated from the data, and is between ∼10 and ∼13 Gyr. The luminosity function of red giant branch (and early-asymptotic giant branch) stars does not show a statistically significant discrepancy with theory. The brightness of the red giant branch bump in the near-infrared is possibly fainter than the models, although the uncertainty on the spectroscopic metallicity and age prevents to reach a firm conclusion on this issue.