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We present abundance measurements, based on high-resolution optical spectroscopic data obtained with the Ultraviolet and Visual Echelle Spectrograph mounted on Kueyen (Very Large Telescope UT2), for ten stars in the extended blue horizontal branch of the Galactic globular cluster NGC 1904 (M79). In agreement with previous findings for other clusters, we obtain normal abundances for stars cooler than $T_{\rm eff}\sim 11\,000$K, and largely anomalous abundances for hotter stars: large He depletions, and overabundances of Fe, Ti, Cr, P and Mn. The abundances of Mg, Si and Ca are roughly normal, in the hot stars as well as in the cooler ones. This abundance pattern can be attributed to the onset of diffusion and to radiation pressure in the stable atmospheres of hot horizontal branch stars.

We present distance modulus and reddening determinations for 72 Galactic globular clusters from the homogeneous photometric database of Piotto et al. ([CITE]), calibrated to the HST flight F439Wand F555Wbands. The distances have been determined by comparison with theoretical absolute magnitudes of the ZAHB. For low and intermediate metallicity clusters, we have estimated the apparent Zero Age Horizontal Branch (ZAHB) magnitude from the RR Lyrae level. For metal rich clusters, the ZAHB magnitude was obtained from the fainter envelope of the red HB. Reddenings have been estimated by comparison of the HST colour-magnitude diagrams (CMD) with ground CMDs of template clusters with low reddening. The homogeneity of both the photometric data and the adopted methodological approach allowed us to obtain highly accurate relative cluster distances and reddenings. Our results are also compared with recent compilations in the literature.

In this paper we estimate the initial He content in about 30% of the Galactic globular clusters (GGCs) from new star counts we have performed on the recently published HST snapshot database of Colour Magnitude Diagrams (Piotto et al. [CITE]). More specifically, we use the so-called R-parameter and estimate the He content from a theoretical calibration based on a recently updated set of stellar evolution models. We performed an accurate statistical analysis in order to assess whether GGCs show a statistically significant spread in their initial He abundances, and whether there is a correlation with the cluster metallicity. As in previous works on the subject, we do not find any significant dependence of the He abundance on the cluster metallicity; this provides an important constraint for models of Galaxy formation and evolution. Apart from GGCs with the bluest Horizontal Branch morphology, the observed spread in the individual helium abundances is statistically compatible with the individual errors. This means that either there is no intrinsic abundance spread among the GGCs, or that this is masked by the errors. In the latter case we have estimated a firm 1σupper limit of 0.019 to the possible intrinsic spread. In case of the GGCs with the bluest Horizontal Branch morphology we detect a significant spread towards higher abundances inconsistent with the individual errors; this can be fully explained by additional effects not accounted for in our theoretical calibrations, which do not affect the abundances estimated for the clusters with redder Horizontal Branch morphology. In the hypothesis that the intrinsic dispersion on the individual He abundances is zero, taking into account the errors on the individual R-parameter estimates, as well as the uncertainties on the cluster metallicity scale and theoretical calibration, we have determined an initial He abundance mass fraction $Y_{\rm GGC}=0.250\pm0.006$. This value is in perfect agreement with current estimates based on Cosmic Microwave Background radiation analyses and cosmological nucleosynthesis computations.

In a previous paper we reported on a discontinuity in the extreme horizontal branch (EHB) of the Galactic globular cluster NGC 6752, which we called the second U-jump. This feature was attributed to a combination of post zero-age horizontal branch evolution and diffusion effects. In this follow-up study we analyze other EHB clusters and show that the second U-jump is a common feature among EHB clusters reaching $T_{\rm eff}\ge 23\,000$K, and that its onset in different clusters converges around $T_{\rm eff}\sim 21\,000$±3000 K. We also present near-ultraviolet diagrams of ωCen and NGC 2808, the only two objects with spectroscopically confirmed “blue hook” stars ($T_{\rm eff}\ge 35\,000$K). We confirm predictions of a photometric discontinuity separating late from early-helium flashers. Moreover, we present empirical evidence that the second U-jump population might be mainly composed of early-helium flashers. Lastly, we revisit the discussion on the ubiquitous nature of the gaps and jumps so far identified in the blue HB tails, suggesting a possible discrete nature of the distribution in temperature of the HB stars.

We present radial and rotation ($v\sin i$) velocity measurements from UVES+VLT high resolution spectra of 61 stars in the blue horizontal branches (HB) of the Galactic globular clusters NGC 1904 (M 79), NGC 2808, NGC 6093 (M 80) and NGC 7078 (M 15). 
The data reduction and the velocity determination, based on cross-correlation techniques, are discussed in detail. Most of this database has been used by Recio-Blanco et al. ([CITE]) in their analysis of the rotation velocity properties of blue HB stars. Here we present additional data for NGC 2808. We confirm the results of the previous paper, in particular, a possible link between the HB jump and the abrupt change in the rotational velocity distribution around $T_{\rm eff}\sim 11\,500$K.

We present observational estimates of the magnitude difference between the luminosity function red giant branch bump and the horizontal branch ($\Delta\mathrm{F555W}^{\mathrm{bump}}_{\mathrm{HB}}$), and of star counts in the bump region ($R_{\mathrm{bump}}$), for a sample of 54 Galactic globular clusters observed by the HST. The large sample of stars resolved in each cluster, and the high photometric accuracy of the data allowed us to detect the bump also in a number of metal poor clusters. To reduce the photometric uncertainties, empirical values are compared with theoretical predictions obtained from a set of updated canonical stellar evolution models which have been transformed directly into the HST flight system. We found an overall qualitative agreement between theory and observations. Quantitative estimates of the confidence level are hampered by current uncertainties on the globular cluster metallicity scale, and by the strong dependence of $\Delta\mathrm{F555W}^{\mathrm{bump}}_{\mathrm{HB}}$on the cluster metallicity. In case of the $R_{\mathrm{bump}}$parameter, which is only weakly affected by the metallicity, we find a very good quantitative agreement between theoretical canonical models and observations. For our full cluster sample the average difference between predicted and observed $R_{\mathrm{bump}}$values is practically negligible, and ranges from -0.002 to -0.028, depending on the employed metallicity scale. The observed dispersion around these values is entirely consistent with the observational errors on $R_{\mathrm{bump}}$. As a comparison, the value of $R_{\mathrm{bump}}$predicted by theory in case of spurious bump detections due to Poisson noise in the stellar counts would be ~0.10 smaller than the observed ones. We have also tested the influence on the predicted $\Delta\mathrm{F555W}^{\mathrm{bump}}_{\mathrm{HB}}$and $R_{\mathrm{bump}}$values of an He-enriched component in the cluster stellar population, as recently suggested by D'Antona et al. ([CITE]). We find that, under reasonable assumptions concerning the size of this He-enriched population and the degree of enrichment, the predicted $\Delta\mathrm{F555W}^{\mathrm{bump}}_{\mathrm{HB}}$and $R_{\mathrm{bump}}$values are only marginally affected.

In this paper we report on a curious feature in the V, ($U-B$) color-magnitude diagrams of globular clusters. In our database, we find that a considerable fraction of blue horizontal branch stars, hotter than the instability strip and cooler than the Grundahl et al. (1999) jump (i.e., $6000 \lesssim T_{\rm eff}\rm (K)\lesssim 10\,000$), have ($U-B$) colors redder than their red giant progenitors. This red incursion is not expected on theoretical grounds, as horizontal branch stars (whose convective regions are less extended than in red giant structures) should not “appear” cooler than a red giant. Analyzing data from different telescopes we show that: 1) the horizontal branch red incursion is strongly dependent on the shape of the adopted Ufilter and to a lesser extent, on the Bfilter; 2) the photometry done with Ufilters that do not encompass the Balmer jump shows the blue horizontal branch red incursion; 3) the occurrence of this feature is also due to the peculiar dependence of the Uand Bmagnitudes on star effective temperature, gravity, and metallicity; 4) theoretical tracks can reproduce the observed horizontal branch morphology, provided that the appropriate (i.e. exactly responding to the filters effectively used in the observations) transmission curve efficiencies are used for deriving color-Tefftransformations; 5) the red incursion extent depends on metallicity.?

We present the complete photometric database and the color-magnitude diagrams for 74 Galactic globular clusters observed with the HST/WFPC2 camera in the $F439W$and $F555W$bands. A detailed discussion of the various reduction steps is also presented, and of the procedures to transform instrumental magnitudes into both the HST $F439W$and $F555W$flight system and the standard Johnson \( B \)and \( V \)systems. We also describe the artificial star experiments which have been performed to derive the star count completeness in all the relevant branches of the color magnitude diagram. The entire photometric database and the completeness function will be made available on the Web immediately after the publication of the present paper.

This paper is a further step in the investigation of the morphology of the color-magnitude diagram of Galactic globular clusters, and the fine-tuning of theoretical models, made possible by the recent observational efforts to build homogeneous photometric databases. In particular, we examine here the calibration of the morphological parameter WHBvs. metallicity, originally proposed by Brocato et al. ([CITE]; B98), which essentially measures the color position of the red-giant branch. We show that the parameter can be used to have a first-order estimate of the cluster metallicity, since the dispersion around the mean trend with [Fe/H] is compatible with the measurement errors. The tight WHB-[Fe/H] relation is then used to show that variations in helium content or age do not affect the parameter, whereas it is strongly influenced by the mixing-length parameter α(as expected). This fact allows us, for the first time, to state that there is no trend of αwith the metal content of a cluster. A thorough examination of the interrelated questions of the α-elements enhancement and the color-Tefftransformations, highlights that there is an urgent need for an independent assessment of which of the two presently accepted metallicity scales is the true indicator of a cluster's iron content. Whatever scenario is adopted, it also appears that a deep revision of the $V-I$-temperature relations is needed.

We present deep Vand Iphotometry for the open cluster NGC 4815 and four surrounding Galactic fields down to a limiting magnitude $V\sim25$. These data are used to study cluster spatial extension by means of star counts, and to derive the luminosity (LF) and mass function (MF). The radius turns out to be $3.6\pm0.3$arcmin at $V=19.0$, whereas the mass is $880\pm230 m_{\odot}$down to $V=20.8$. From the color-magnitude diagram, we obtain the LFs in the Vand Ibands, using both the standard histogram and an adaptive kernel. After correction for incompleteness and field star contamination, the LFs were transformed into the present day mass functions (PDMF). The PDMFs from the Vand Iphotometry can be represented as a power-law with a slope $\alpha = 3.1\pm0.3$and $\alpha = 2.9\pm0.3$(the (Salpeter [CITE]) MF in this notation has a slope $\alpha = 2.35$) respectively, in the mass range $2.5 \leq \frac{m}{m_{\odot}} \leq 0.8$. Below this mass, the MF cannot be considered as representative of the cluster IMF, as it is the result of the combined effect of strong irregularities in the stellar background, probable internal dynamical evolution of the cluster and/or interaction of the cluster with the dense Galactic field. Unresolved binaries and mass segregation can only flatten the apparent derived IMF, so we expect that the real IMF must be steeper than the quoted slope by an unknown amount.

In this paper we investigate the level of agreement between observations and "new" Asymptotic Giant Branch (AGB) models, as produced by updating the physical inputs adopted in previous stellar computations. One finds that the new physics increases the predicted luminosity of Horizontal Branch (HB) and AGB stellar structures by a similar amount, keeping unchanged the predictions about the difference in luminosity between these two evolutionary phases. The best fit of selected globular clusters appears rather satisfactory, disclosing the relevance of the assumption on the mass of the Red Giant Branch (RGB) progenitor in assessing the distance modulus of moderately metal rich clusters. The still existing uncertainties related either to the input physics or to the efficiency of some macroscopic mechanisms, like convection or microscopic diffusion, are critically discussed, ruling out the occurrence of the so called "breathing pulses" during the central He exhaustion, in agreement with earlier suggestions.

In this paper we present the second and final part of a large and photometrically homogeneous CCD color-magnitude diagram (CMD) data base, comprising 52 nearby Galactic globular clusters (GGC) imaged in the Vand Ibands.
The catalog has been collected using only two telescopes (one for each hemisphere). The observed clusters represent $75\%$of the known Galactic globulars with $(m-M)_V\leq 16.15$mag, cover most of the globular cluster metallicity range ($-2.2 \leq {\rm [Fe/H]}\leq -0.4$), and span Galactocentric distances from $\sim1.2$to $\sim18.5$kpc.
In particular, here we present the CMDs for the 13 GGCs observed in the Northern hemisphere. The remaining 39 Southern hemisphere clusters of the catalog have been presented in a companion paper (Rosenberg et al. 2000). We present the first CCD color magnitude diagram for NGC 6779 (M 56).
All the CMDs extend from at least $\sim2$magnitudes below the turn-off (i.e. $V_{\rm lim}\geq22$) to the tip of the red giant branch. The calibration has been done using a large number of standard stars, and the absolute calibration is reliable to a $\sim0.02$mag level in both filters.
This catalog, because of its homogeneity, is expected to represent a useful data base for the measurement of the main absolute and relative parameters characterizing the CMD of GGCs.

We present the first part of the first large and homogeneous CCD color-magnitude diagram (CMD) data base, comprising 52 nearby Galactic globular clusters (GGC) imaged in the Vand Ibands using only two telescopes (one for each hemisphere). The observed clusters represent $75\%$of the known Galactic globulars with $(m-M)_V\leq 16.15$mag, cover most of the globular cluster metallicity range ($-2.2 \leq {\rm [Fe/H]}\leq -0.4$), and span Galactocentric distances from $\sim1.2$to $\sim18.5$kpc.
In this paper, the CMDs for the 39 GGCs observed in the southern hemisphere are presented. The remaining 13 northern hemisphere clusters of the catalog are presented in a companion paper. For four clusters (NGC 4833, NGC 5986, NGC 6543, and NGC 6638) we present for the first time a CMD from CCD data. The typical CMD span from the 22ndVmagnitude to the tip of the red giant branch. Based on a large number of standard stars, the absolute photometric calibration is reliable to the $\sim0.02$mag level in both filters.
This catalog, because of its homogeneity, is expected to represent a useful data base for the measurement of the main absolute and relative parameters characterizing the CMD of GGCs.

We present abundances of Fe, Na, and O for 1409 red giant stars in 15?galactic globular clusters (GCs), derived from the homogeneous analysis of high-resolution FLAMES/GIRAFFE spectra. Combining the present data with results from our FLAMES/UVES spectra and from previous studies within the project, we obtained a total sample of 1958 stars in 19?clusters, the largest and most homogeneous database of this kind to date. The programme clusters cover a range in metallicity from [Fe/H] = -2.4?dex to [Fe/H] = -0.4?dex, with a wide variety of global parameters (morphology of the horizontal branch, mass, concentration, etc.). For all clusters we find the Na-O anticorrelation, the classical signature of the operation of proton-capture reactions in H-burning at high temperature in a previous generation of more massive stars that are now extinct. Using quantitative criteria (from the morphology and extension of the Na-O anticorrelation), we can define three different components of the stellar population in GCs. We separate a primordial component?(P) of first-generation stars, and two components of second-generation stars, that we name intermediate?(I) and extreme?(E) populations from their different chemical composition. The P component is present in all clusters, and its fraction is almost constant at about one third. The I?component represents the bulk of the cluster population. On the other hand, E?component is not present in all clusters, and it is more conspicuous in some (but not in all) of the most massive clusters. We discuss the fractions and spatial distributions of these components in our sample and in two additional clusters (M?3?=?NGC?5272 and M?13?=?NGC6205) with large sets of stars analysed in the literature. We also find that the slope of the anti-correlation (defined by the minimum?O and maximum Na?abundances) changes from cluster-to-cluster, a change that is represented well by a bilinear relation on cluster metallicity and luminosity. This second dependence suggests a correlation between average mass of polluters and cluster mass.

Context. Deep photometry of crowded fields, such as Galactic globular clusters, is severely limited by the resolution of ground-based telescopes. On the other hand, the Hubble Space Telescope does not have the near-infrared (NIR) filters needed to allow large color baselines.Aims. In this work we demonstrate how ground based observations can reach the required resolution when using Multi-Conjugated Adaptive Optic (MCAO) devices in the NIR, such as the experimental infrared camera (MAD) available on the VLT. This is particularly important since these corrections are planned to be available on all ground-based telescopes in the near future.Methods. We demonstrate this by combining the infrared photometry obtained by MAD/VLT with ACS/HST optical photometry of our scientific target, the bulge globular cluster NGC?6388, in which we imaged two fields. In particular, we constructed color-magnitude diagrams with an extremely wide color baseline in order to investigate the presence of multiple stellar populations in this cluster.Results. From the analysis of the external field, observed with better seeing conditions, we derived the deepest optical-NIR?CMD of NGC?6388 to date. The high-precision photometry reveals that two distinct sub-giant branches are clearly present in this cluster. We also use the CMD from the central region to estimate the distance [ (m-M)?=15.33] and the reddening (E(B-V)=0.38) for this cluster. We estimate the age to be (~11.5?1.5?Gyr). The large relative-age error reflects the bimodal distribution of the SGB stars.Conclusions. This study clearly demonstrates how MCAO correction in the NIR bands implemented on ground based telescopes can complement the high-resolution optical data from HST.

We have analyzed ACS/WFC and WFPC2 images from HST, as well as ground-based data to study the radial distribution of the double sub-giant branch (SGB) recently discovered in the Galactic globular cluster NGC 1851. We found that the SGB split can be followed all the way from the cluster center out to at least 8??from the center. Beyond this distance out to the tidal radius at ~11.7?arcmin, there are simply too few SGB stars to identify the sequences. The number ratio of the bright SGB to the faint SGB stars shows no significant radial trend. Furthermore, we have found that the ratio of blue horizontal-branch (HB) stars plus RR Lyrae to the red HB stars also remains constant from the cluster center to the outer envelope.

Context. ??Centauri is the most well studied Galactic Globular Cluster because of its numerous puzzling features: significant dispersion in metallicity, multiple populations, triple main-sequence, horizontal branch morphology, He-rich population(s), and extended star-formation history. Intensive spectroscopic follow-up observing campaigns targeting stars at different positions in the color?magnitude diagram promises to clarify some of these peculiarities.Aims. To be able to target cluster members reliably during spectroscopic surveys and both spatial and radial distributions in the cluster outskirts without including field stars, a high quality proper-motion catalog of ??Cen?and membership probability determination are required. The only available wide field proper-motion catalog of ??Cen?is derived from photographic plates, and only for stars brighter than B~16. Using ESO archive data, we create a new, CCD-based, proper-motion catalog for this cluster, extending to B~20.Methods. We used high precision astrometric software developed specifically for data acquired by WFI@2.2m telescope and presented in the first paper of this series. We demonstrated previously that a 7?mas astrometric precision level can be achieved with this telescope and camera for well exposed stars in a single exposure, assuming an empirical PSF and a local transformation approach in measuring star displacements.Results. We achieved a good cluster-field separation with a temporal base-line of only four years. We corrected our photometry for sky-concentration effects. We provide calibrated photometry for UBVRCICwide-band data plus narrow-band filter data centered on H?for almost 360?000?stars. We confirm that the ??Cen?metal-poor and metal-rich components have the same proper motion, and demonstrate that the metal-intermediate component in addition exhibits the same mean motion as the other RGB stars. We provide membership probability determinations for published ??Cen?variable star catalogs.Conclusions. Our catalog extends the proper-motion measurements to fainter than the cluster turn-off luminosity, and covers a wide area [Formula: see text](?33[Formula: see text] around the center of ??Cen. Our catalog is electronically available to the astronomical community.

Aims. We present a large multi-epoch high resolution spectroscopic investigation searching for binary candidates in the Galactic Globular Cluster (GGC) M4. The aim of our work is the identification of binary candidates, and the determination of the binary fraction and of the binary radial distribution.Methods. We have obtained 5973 individual spectra of 2469?stars with the multifiber facility FLAMES+GIRAFFE at VLT. Selected stars range from the red giant branch tip to one magnitude below the TO, and cover the entire cluster. Each star has been observed at least twice, with a temporal interval of about three years. For 484?stars we have three epochs. Radial velocities were obtained with the classical cross-correlation technique, using a solar type spectrum as the template.Results. The average radial velocity of the observed cluster members is 70.29 ? 0.07 (? 0.3)(? 0.1)?km?s-1. The search for variations in radial velocities among the stars with multi-epoch observations yielded 57?binary star candidates. Our radial velocity measurement accuracy allowed us to identify at a 3??level binaries with radial velocity variations larger than ~0.3?km?s-1for the target stars with V?15, and larger than ~0.5?km?s-1for the targets with V?15. We identified 4?binary star candidates out of 97?observed targets inside the core radius, and 53?candidates out of 2372?observed stars outside the core radius. Accounting for the incompleteness affecting our survey, the lower limit for the total binary fraction is f = 3.0 ? 0.3%. The lower limit for the binary fraction in the cluster core is f = 5.1 ? 2.3%, while outside the core it decreases to f = 3.0 ? 0.4%. Similarly, we found f = 4.5 ? 0.4% and f = 1.8 ? 0.6% for the binary fraction inside and outside the half mass radius.

Context. We present a photometric and astrometric catalog of 187?963 stars located in the field around the old super-metal-rich Galactic open cluster NGC?6253. The total field-of-view covered by the catalog is 34??33?. In this field, we provide CCD BVRI?photometry. For a smaller region close to the cluster's center, we also provide near-infrared JHK?photometry.Aims. We analyze the properties of NGC?6253 by using our new photometric data and astrometric membership.Methods. In June 2004, we targeted the cluster during a 10?day multi-site campaign, which involved the MPG/ESO 2.2?m telescope with its wide-field imager and the Anglo-Australian 3.9?m telescope, equipped with the IRIS2 near-infrared imager. Archival CCD images of NGC?6253 were used to derive relative proper motions and to calculate the cluster membership probabilities.Results. We have refined the cluster's fundamental parameters, deriving (V0-Mv)=11.15, E(B - V) = 0.15, E(V - I) = 0.25, E(V - J) = 0.50, and E(V - H) = 0.55. The color excess ratios obtained using both the optical and near infrared colors indicate a normal reddening law in the direction of NGC?6253. The age of NGC?6253 at 3.5?Gyr, determined from our best-fitting isochrone appears to be slightly older than the previous estimates. Finally, we estimated the binary fraction among the cluster members to be ~20%-30% and identified 11?blue straggler candidates.

We present a chemical abundance analysis based on high resolution UVES spectra of seventeen bright giant stars in the Globular Cluster (GC) M?22. We obtained an average iron abundance of [Fe/H] = -1.76?0.02 (internal errors only) and an ? enhancement of 0.36?0.04 (internal errors only). Na and O, and Al and O follow the well known anticorrelations found in many other?GCs. We identified two groups of stars with significantly different abundances of the s-process elements?Y, Zr, and Ba. The relative numbers of the two group members are very similar to the ratio of the number of stars in the two sub giant branches (SGB) of M?22. Y and Ba?abundances do not correlate with Na, O, and Al. The s-element rich stars are also richer in iron and have higher Ca abundances. The results from high resolution spectra were confirmed by analyses of lower resolution GIRAFFE spectra of fourteen additional M?22?stars. The analyses of the GIRAFFE spectra also show that the Eu ? a pure r-process element ? abundance is not related to the iron content. We discuss the chemical abundance pattern of M?22 stars in the context of GC multiple stellar populations phenomenon.??

Aims. We present abundance analysis based on high resolution spectra of 105?isolated red giant branch (RGB)?stars in the Galactic Globular Cluster NGC?6121?(M?4). Our aim is to study its star population in the context of the multi-population phenomenon recently discovered to affect some Globular Clusters.Methods. The data have been collected with FLAMES+UVES, the multi-fiber high resolution facility at the ESO/VLT@UT2?telescope. Analysis was performed under LTE approximation for the following elements: O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Ba, and?NLTE corrections were applied to those (Na, Mg) strongly affected by departure from?LTE. Spectroscopic data were coupled with high-precision wide-field UBVICphotometry from WFI@2.2?m?telescope and infrared JHK photometry from 2MASS.Results. We derived an average [Fe/H] = -1.07?0.01 (internal error), and an?? enhancement of [?/Fe] = +0.39?0.05?dex (internal error). We confirm the presence of an extended Na-O?anticorrelation, and find two distinct groups of stars with significantly different?Na and O?content. We find no evidence of a Mg-Al?anticorrelation. By coupling our results with previous studies on the CN?band strength, we find that the CN?strong stars have higher?Na and Al?content and are more O depleted than the CN?weak ones. The two groups of Na-rich, CN-strong and Na-poor, CN-weak stars populate two different regions along the?RGB. The Na-rich group defines a narrow sequence on the red side of the RGB, while the Na-poor sample populate a bluer, more spread portion of the RGB. In the U vs.? U-B?color magnitude diagram the RGB?spread is present from the base of the?RGB to the RGB-tip. Apparently, both spectroscopic and photometric results imply the presence of two stellar populations in?M?4. We briefly discuss the possible origin of these populations.

Context. The solar-age open cluster M?67 (C0847+120, NGC?2682) is a touchstone in studies of the old Galactic disk. Despite its outstanding role, the census of cluster membership for M?67 at fainter magnitudes and their properties are not well-established.Aims. Using proprietary and archival ESO data, we have obtained astrometric, photometric, and radial velocities of stars in a 34?33?arcmin2field centered on the old open cluster M?67.Methods. The two-epoch archival observations separated by 4?years and acquired with the Wide-Field Imager at the 2.2?m MPG/ESO telescope were reduced with our new astrometric techniques, as described in the first paper in this series. The same observations served to derive calibrated BVI photometry in M?67. Radial velocities were measured using the archival and new spectroscopic data obtained at the VLT.Results. We have determined relative proper motions and membership probabilities for ~2400?stars. The precision of proper motions for optimally exposed stars is 1.9?mas?yr-1, gradually degrading down to ~5?mas?yr-1at V=20. Our relatively precise proper motions at V>16 were first obtained in this magnitude range for M?67. Radial velocities were measured for 211?stars in the same field. We also present a detailed comparison with recent theoretical isochrones from several independent groups.Conclusions. For the M?67 area, we provide positions, calibrated BVI photometry, relative proper motions, membership probabilities, and radial velocities. We demonstrate that ground-based CCD mosaic observations just a few years apart are producing proper motions, allowing reliable membership determination. We have produced a catalog that is electronically available to the astronomical community.

Proper-motion, star counts and photometric catalog simulations are used to explain the detected stellar over-density in the region of Canis Major, claimed to be the core of a disrupted dwarf galaxy (CMa, Martin et al. [CITE], MNRAS, 348, 12; Bellazzini et al. [CITE], [arXiv:astro-ph/0311119]), as due to the Galactic warp and flare in the external disk. We compare the kinematics of CMa M-giant selected sample with surrounding Galactic disk stars in the UCAC2 catalog and find no peculiar proper motion signature: CMa stars mimic thick disk kinematics. Moreover, when taking into account the Galactic warp and flare of the disk, 2MASS star count profiles reproduce the CMa stellar over-density. This star count analysis is confirmed by direct comparison with synthetic color-magnitude diagrams simulated with the Besançon models (Robin et al.  [CITE], A&A, 409, 523) that include the warp and flare of the disk. The presented evidence casts doubt on the identification of the CMa over-density as the core of a disrupted Milky Way satellite. This however does not make clear the origin of over-densities responsible for the ring structure in the anticenter direction of the Galactic halo (Newberg et al.  [CITE], ApJ, 569, 245; Yanny et al. 2003, ApJ, 588, 824).

In this paper we present the second and final part of a large and photometrically homogeneous CCD color-magnitude diagram (CMD) data base, comprising 52 nearby Galactic globular clusters (GGC) imaged in the $V$ and $I$ bands. The catalog has been collected using only two telescopes (one for each hemisphere). The observed clusters represent $75\%$ of the known Galactic globulars with $(m-M)_Veq 16.15$ mag, cover most of the globular cluster metallicity range ( $-2.2 eq { m [Fe/H]}eq -0.4$ ), and span Galactocentric distances from $\sim1.2$ to $\sim18.5$ kpc. In particular, here we present the CMDs for the 13 GGCs observed in the Northern hemisphere. The remaining 39 Southern hemisphere clusters of the catalog have been presented in a companion paper (Rosenberg et al. [CITE]). We present the first CCD color magnitude diagram for NGC 6779 (M 56). All the CMDs extend from at least $\sim2$ magnitudes below the turn-off (i.e. $V_{ m lim}\geq22$ ) to the tip of the red giant branch. The calibration has been done using a large number of standard stars, and the absolute calibration is reliable to a $\sim0.02$ mag level in both filters. This catalog, because of its homogeneity, is expected to represent a useful data base for the measurement of the main absolute and relative parameters characterizing the CMD of GGCs.

We estimate the empirical R-parameter in 26 Galactic globular clusters covering a wide metallicity range, imaged by Wide Field Planetary Camera 2 on board the Hubble Space Telescope. The improved spatial resolution permits a large fraction of evolved stars to be measured and permits accurate assessment of radial population gradients and completeness corrections. In order to evaluate both the He abundance and the He-to-metal enrichment ratio, we construct a large set of evolutionary models by adopting similar metallicities and different He contents. We find an absolute He abundance that is lower than that estimated from spectroscopic measurements in H IIregions and from primordial nucleosynthesis models. This discrepancy could be removed by adopting a 12C(?,?)16O nuclear cross section about a factor of 2 smaller than the canonical value, although different assumptions for mixing processes also can introduce systematic effects.