Yazan Momany - Academia.edu (original) (raw)

Papers by Yazan Momany

Proceedings of the International Astronomical Union, 2006

We present a preliminary reconstruction of the star formation history of the Sagittarius dwarf ir... more We present a preliminary reconstruction of the star formation history of the Sagittarius dwarf irregular galaxy (SagDIG), a dIrr galaxy at the border of the Local Group. SagDIG is a lively star-forming dwarf galaxy with very low metallicity and an abundant gas reservoir, for which deep HST ACS observations have been obtained . We have built synthetic color-magnitude diagrams in the intrinsic ACS bands F606W and F814W and compared them with our HST/ACS observations to derive the global star formation history of the galaxy. We find a broad episode of star formation between 3 and 8 Gyr ago, with a low-intensity tail of star formation at older ages, and a SF enhancement in the last Gyr. An upper limit to the old populations is set by modeling the old HB. Our modeling of the color-magnitude diagram also provides some constraints on the chemical enrichment history of SagDIG.

DEALING WITH TURBULENCE: MCAO EXPERIENCE AND BEYOND

Optical Turbulence, 2009

ABSTRACT Multi Conjugated Adaptive Optics, thanks to the Multi Conjugated Adaptive optics Demonst... more ABSTRACT Multi Conjugated Adaptive Optics, thanks to the Multi Conjugated Adaptive optics Demonstrator, MAD, of European Southern Observatory, entered in the realm of producing astronomical science after more than a decade. I review our experience with the Layer Oriented Wavefront Sensor paying special attention to the practical influence of the encountered atmospheric turbulence on the achieved science. An outcome, maybe very personal, of the perspective in the near and not so near future are outlined.

H and Ks photometry of Trumpler 14 (Sana+, 2010)

We present adaptive optics (AO) near-infrared observations of the core of the Tr 14 cluster in th... more We present adaptive optics (AO) near-infrared observations of the core of the Tr 14 cluster in the Carina region obtained with the ESO multi-conjugate AO demonstrator, MAD. Our campaign yields AO-corrected observations with an image quality of about 0.2' across the 2" field of view, which is the widest AO mosaic ever obtained. We detected almost 2000 sources spanning a

Abundance anomalies in NGC 2808

We present metallicity measurements of 25 stars in the blue horizontal branch of the Galactic glo... more We present metallicity measurements of 25 stars in the blue horizontal branch of the Galactic globular cluster NGC 2808. Our measurements are based on moderate-resolution spectra taken with the multi-object fiber facility FLAMES-UVES, mounted on Kueyen at the Very Large Telescope. We confirm that stars hotter than a threshold temperature have super-solar abundance, while the cooler ones respect the nominal metallicity of the cluster, i.e. [Fe/H] ~ -1.1. The threshold temperature is estimated to be about 12000 K, corresponding to the so called u-jump, and coincides with the sudden departure of the cluster horizontal branch from the models. The metallicity increases with temperature for star hotter than the jump, confirming the hypothesis that the process responsible for this abrupt metallic enhancement is the levitation due to the strong radiation field in absence of a significative convective envelope. A metallicity dependence of the abundance enhancement is also suggested, with mor...

The globular cluster HP1 is projected on the bulge, very close to the Galactic center. The Multi-... more The globular cluster HP1 is projected on the bulge, very close to the Galactic center. The Multi-Conjugate Adaptive Optics (MCAO) Demonstrator (MAD) at the Very Large Telescope (VLT) allowed to acquire high resolution deep images that, combined with first epoch New Technology Telescope (NTT) data, enabled to derive accurate proper motions. The cluster and bulge field stellar contents were disentangled by means of this process, and produced unprecedented definition in the color-magnitude diagrams for this cluster. The metallicity of [Fe/H] ~ -1.0 from previous spectroscopic analysis is confirmed, which together with an extended blue horizontal branch, imply an age older than the halo average. Orbit reconstruction results suggest that HP1 is spatially confined within the bulge.

Astronomy and Astrophysics

We have obtained deep BVI CCD photometry of Phoenix, a galaxy considered a transition case betwee... more We have obtained deep BVI CCD photometry of Phoenix, a galaxy considered a transition case between dwarf spheroidal and dwarf irregular galaxies. A comparison of our data with the RGBs of Galactic globular clusters gives a mean metal abundance [Fe/H] = -1.81+/-0.10 dex. The presence of an intrinsic color dispersion in the upper red RGB suggests an abundance range of about 0.5 dex, although a range in age may also affect the RGB width. For the first time, a HB has been revealed at V~23.8. The HB is predominantly red yet moderately extended to the blue, which indicates the presence of a significant population with age comparable to that of old halo GGCs. This HB morphology in a metal-poor system indicates a mild "second parameter" effect. From the mean level of the HB we derived a true distance modulus 23.21+/-0.08, in good agreement with the distance modulus 23.04+/-0.07 estimated from the cutoff of the RGB at I~23.1. We find a radial gradient in the HB morphology, and our ...

Pismis 23 and Stephenson 2 VI photometry (Ortolani+, 2002)

Pismis 23 and Stephenson 2 are two very reddened open clusters, projected close to the Galactic p... more Pismis 23 and Stephenson 2 are two very reddened open clusters, projected close to the Galactic plane. We present VI and JH photometry for Pismis 23 and I and Gunn z for Stephenson 2. We derive a relatively old age of ~700Myr for Pismis 23, with a reddening value of E(B-V)=1.73 and a distance d&sun;~2.6kpc from the Sun. Stephenson 2 has a clump of red supergiants, indicating a young age of about 20Myr, somewhat younger and more distant (d&sun;~6kpc) than recently reported in the literature. The age estimate for such a young object is crucial for the distance estimate. The high reddening of these two clusters relative to predictions from the diffuse interstellar medium at their distances is due to discrete intervening clouds. (2 data files).

We present new observations of Sextans and Leo I dwarf galaxies, that provide new insight on thei... more We present new observations of Sextans and Leo I dwarf galaxies, that provide new insight on their stellar populations. The large sample of stars measured in Sextans allowed us to obtain a reliable estimate of the metal content of this galaxy, to study the population spatial gradients, and to investigate the nature of the large number of blue stragglers. In Leo I, we discovered a significant population of RR Lyrae variables. The analysis of the pulsational properties of the detected variables suggests that this galaxy is an Oosterhoff intermediate object, similar to the LMC and to other dwarf galaxies in the Local Group.

Recent results on the detection of substructure in dwarf spheroidal galaxies are discussed. In mo... more Recent results on the detection of substructure in dwarf spheroidal galaxies are discussed. In most cases they show that, when a galaxy experiences multiple SF episodes, the intermediate age population is more centrally concentrated than the old population, and that the recent SF is even more concentrated towards the central regions. Moreover, it appears that the spatial distribution of stars becomes more and more irregular as younger and younger subpopulations are considered. We illustrate how wide-area observations, allowing a substantial coverage of dwarf spheroidals (in particular the satellites of the Milky Way), has provided evidence for cosmologically old populations in every dSph galaxy. All these results are placed in the broader scenario of population gradients in nearby dwarf galaxies of different morphological types.

Halo and Disk-like Components in Nearby Dwarf Galaxies

New deep observations at the ESO VLT and NTT were used to study the spatial distribution of stell... more New deep observations at the ESO VLT and NTT were used to study the spatial distribution of stellar populations with different ages in three distant Local Group dwarf galaxies. In all of them, recently formed stars are preferentially found in the central regions, embedded in a sheet of red, older stars. In the case of Antlia and SagDIG, the extended component is likely to be a disk rather than a spheroidal halo.

Proceedings of the International Astronomical Union

We present deep V, I photometry of the globular cluster Terzan 7, a probable member of the globul... more We present deep V, I photometry of the globular cluster Terzan 7, a probable member of the globular cluster system of the Sagittarius dwarf spheroidal galaxy. The metallicity, estimated from a new method based on analytic RGB fits, agrees with previous estimates based on color-magnitude diagrams ([Fe/H]= -0.9 ± 0.1 dex). This result confirms a discrepancy between photometric and spectroscopic determinations. Using both the horizontal and vertical methods to estimate relative ages, we confirm that the age of Terzan 7 is about 70% that of 47 Tuc. A rich population of blue stragglers is found, strongly concentrated toward the center of the cluster.

B and V photometry of the metal-rich bulge globular cluster NGC 6304

Astronomy and Astrophysics

We present B and V photometry of the bulge globular cluster NGC 6304. We derive a reddening E(B-V... more We present B and V photometry of the bulge globular cluster NGC 6304. We derive a reddening E(B-V) ~ 0.5 and a distance from the Sun dsun ~ 6 kpc. From the red giant branch morphology we estimate that the metallicity of NGC 6304 is intermediate between those of 47 Tuc and NGC 6528. The cluster is foreground to the bulk of the bulge population and the reddenings are comparable. Evidence of a hot stellar component belonging to the cluster is found. These hot stars could correspond to a blue extended horizontal branch and/or blue stragglers. Observations collected at the European Southern Observatory -- ESO, Chile, proposal no. 61.E-0335

Infrared Observations of Young Star Clusters

Star-Cluster Astrometry with Ground-Based Wide Field Imagers

We show the astrometric potential of the Wide Field Imager at the focus of the MPI-ESO 2.2m Teles... more We show the astrometric potential of the Wide Field Imager at the focus of the MPI-ESO 2.2m Telescope. Currently, we are able to measure the position of a well-exposed star with a precision of sim\simsim4 mas/frame in each coordinate (under 0.8 arcsec seeing conditions). We present some preliminary results here.

Abundances of red giants in NGC 6441 (Gratton+, 2006)

Equivalent widths for 5 giants members of the globular cluster NGC6441 (Table 3) and 7 field gian... more Equivalent widths for 5 giants members of the globular cluster NGC6441 (Table 3) and 7 field giants (Table 4) (3 data files).

Abundances of red giants in NGC 6388 (Carretta+, 2007)

Spectra for 13 RGB stars in NGC 6388 were obtained with UVES/FLAMES@VLT; based on radial velocity... more Spectra for 13 RGB stars in NGC 6388 were obtained with UVES/FLAMES@VLT; based on radial velocity, 7 of them resulted member stars. Abundances of Fe, O, Na, alpha-elements and heavier elements were derived using equivalent widths, model atmospheres and atmospheric parameters based on photometry. For each star we give identification, equatorial coordinates, VBIJK magnitudes, heliocentric radial velocity. For the 7 member stars we also present Teff, logg, [A/H], v_t, [Fe/H], [O/Fe], [Na/Fe], [Mg/Fe], [Al/Fe], [Si/Fe], [Ca/Fe], [Sc/Fe], [Ti/Fe], [V/Fe], [Cr/Fe], [Mn/Fe], [Co/Fe], [Ni/Fe], [Y/Fe], [Zr/Fe], [Ba/Fe], [La/Fe], [Ce/Fe], and [Eu/Fe]. We present here the EWs for all the above elements for the 7 member stars. (2 data files).

Abundances of red giants in NGC 6752 (Carretta+, 2007)

Spectra for 151 RGB stars in NGC 6752 were obtained with FLAMES@VLT using two gratings (HR11, HR1... more Spectra for 151 RGB stars in NGC 6752 were obtained with FLAMES@VLT using two gratings (HR11, HR13). Abundances of Fe, O, Na were derived using equivalent widths, model atmospheres and atmospheric parameters based on photometry. For each star we give identification, equatorial coordinates, VBJK magnitudes, S/N, heliocentric radial velocity for both gratings, Teff, logg, [A/H], vt, [Fe/H], [O/Fe], [Na/Fe]. Equivalent widths are given in tablea. (4 data files).

Evolved Stellar Populations in Nearby Galaxies: The Near-Infrared Perspective

We present near-infrared observations of the distant Milky Way satellite galaxies Leo I and Leo I... more We present near-infrared observations of the distant Milky Way satellite galaxies Leo I and Leo II, obtained with the new wide-field imager WFCAM at the UKIRT telescope as part of a study of evolved stars (Red Giant and Asymptotic Giant Branch stars) in Local Group dwarf spheroidal galaxies. Optical-infrared colors, which are more accurate metallicity indicators than optical or infrared colors alone, have been used to estimate the metallicity distribution of the red giant stars. Using near-infrared magnitudes and colors of luminous asymptotic giant branch (AGB) stars we have been able to discriminate carbon- and oxygen-rich AGB stars and derive their distributions in bolometric luminosity. In turn, the properties of AGB stars in different galactic environments will provide information on the star-formation histories of the parent galaxies.

JHK photometry of Fornax red giant branch (Gullieuszik+, 2007)

The catalogues of the upper red giant branch stars in Fornax dwarf Spheroidal galaxy are obtained... more The catalogues of the upper red giant branch stars in Fornax dwarf Spheroidal galaxy are obtained from ground-based SOFI@NTT observations. The shallow catalogue is obtained from a mosaic of 16 SOFI fields and covers an area of 18.5x18.5arcmin. The deep catalogue covers an area of 4.5x4.5arcmin. (2 data files).

Abundances of NGC 6121 red giants (Marino+, 2008)

Table 8 contains the equatorial coordinates, the atmospheric parameters measured on UVES spectra,... more Table 8 contains the equatorial coordinates, the atmospheric parameters measured on UVES spectra, UBVI_C photometry from WFI@2.2m telescope and infrared JHK photometry from 2MASS for the analysed stars. Table 9 contains the measured chemical abundances. (2 data files).

Proceedings of the International Astronomical Union, 2006

We present a preliminary reconstruction of the star formation history of the Sagittarius dwarf ir... more We present a preliminary reconstruction of the star formation history of the Sagittarius dwarf irregular galaxy (SagDIG), a dIrr galaxy at the border of the Local Group. SagDIG is a lively star-forming dwarf galaxy with very low metallicity and an abundant gas reservoir, for which deep HST ACS observations have been obtained . We have built synthetic color-magnitude diagrams in the intrinsic ACS bands F606W and F814W and compared them with our HST/ACS observations to derive the global star formation history of the galaxy. We find a broad episode of star formation between 3 and 8 Gyr ago, with a low-intensity tail of star formation at older ages, and a SF enhancement in the last Gyr. An upper limit to the old populations is set by modeling the old HB. Our modeling of the color-magnitude diagram also provides some constraints on the chemical enrichment history of SagDIG.

DEALING WITH TURBULENCE: MCAO EXPERIENCE AND BEYOND

Optical Turbulence, 2009

ABSTRACT Multi Conjugated Adaptive Optics, thanks to the Multi Conjugated Adaptive optics Demonst... more ABSTRACT Multi Conjugated Adaptive Optics, thanks to the Multi Conjugated Adaptive optics Demonstrator, MAD, of European Southern Observatory, entered in the realm of producing astronomical science after more than a decade. I review our experience with the Layer Oriented Wavefront Sensor paying special attention to the practical influence of the encountered atmospheric turbulence on the achieved science. An outcome, maybe very personal, of the perspective in the near and not so near future are outlined.

H and Ks photometry of Trumpler 14 (Sana+, 2010)

We present adaptive optics (AO) near-infrared observations of the core of the Tr 14 cluster in th... more We present adaptive optics (AO) near-infrared observations of the core of the Tr 14 cluster in the Carina region obtained with the ESO multi-conjugate AO demonstrator, MAD. Our campaign yields AO-corrected observations with an image quality of about 0.2' across the 2" field of view, which is the widest AO mosaic ever obtained. We detected almost 2000 sources spanning a

Abundance anomalies in NGC 2808

We present metallicity measurements of 25 stars in the blue horizontal branch of the Galactic glo... more We present metallicity measurements of 25 stars in the blue horizontal branch of the Galactic globular cluster NGC 2808. Our measurements are based on moderate-resolution spectra taken with the multi-object fiber facility FLAMES-UVES, mounted on Kueyen at the Very Large Telescope. We confirm that stars hotter than a threshold temperature have super-solar abundance, while the cooler ones respect the nominal metallicity of the cluster, i.e. [Fe/H] ~ -1.1. The threshold temperature is estimated to be about 12000 K, corresponding to the so called u-jump, and coincides with the sudden departure of the cluster horizontal branch from the models. The metallicity increases with temperature for star hotter than the jump, confirming the hypothesis that the process responsible for this abrupt metallic enhancement is the levitation due to the strong radiation field in absence of a significative convective envelope. A metallicity dependence of the abundance enhancement is also suggested, with mor...

The globular cluster HP1 is projected on the bulge, very close to the Galactic center. The Multi-... more The globular cluster HP1 is projected on the bulge, very close to the Galactic center. The Multi-Conjugate Adaptive Optics (MCAO) Demonstrator (MAD) at the Very Large Telescope (VLT) allowed to acquire high resolution deep images that, combined with first epoch New Technology Telescope (NTT) data, enabled to derive accurate proper motions. The cluster and bulge field stellar contents were disentangled by means of this process, and produced unprecedented definition in the color-magnitude diagrams for this cluster. The metallicity of [Fe/H] ~ -1.0 from previous spectroscopic analysis is confirmed, which together with an extended blue horizontal branch, imply an age older than the halo average. Orbit reconstruction results suggest that HP1 is spatially confined within the bulge.

Astronomy and Astrophysics

We have obtained deep BVI CCD photometry of Phoenix, a galaxy considered a transition case betwee... more We have obtained deep BVI CCD photometry of Phoenix, a galaxy considered a transition case between dwarf spheroidal and dwarf irregular galaxies. A comparison of our data with the RGBs of Galactic globular clusters gives a mean metal abundance [Fe/H] = -1.81+/-0.10 dex. The presence of an intrinsic color dispersion in the upper red RGB suggests an abundance range of about 0.5 dex, although a range in age may also affect the RGB width. For the first time, a HB has been revealed at V~23.8. The HB is predominantly red yet moderately extended to the blue, which indicates the presence of a significant population with age comparable to that of old halo GGCs. This HB morphology in a metal-poor system indicates a mild "second parameter" effect. From the mean level of the HB we derived a true distance modulus 23.21+/-0.08, in good agreement with the distance modulus 23.04+/-0.07 estimated from the cutoff of the RGB at I~23.1. We find a radial gradient in the HB morphology, and our ...

Pismis 23 and Stephenson 2 VI photometry (Ortolani+, 2002)

Pismis 23 and Stephenson 2 are two very reddened open clusters, projected close to the Galactic p... more Pismis 23 and Stephenson 2 are two very reddened open clusters, projected close to the Galactic plane. We present VI and JH photometry for Pismis 23 and I and Gunn z for Stephenson 2. We derive a relatively old age of ~700Myr for Pismis 23, with a reddening value of E(B-V)=1.73 and a distance d&sun;~2.6kpc from the Sun. Stephenson 2 has a clump of red supergiants, indicating a young age of about 20Myr, somewhat younger and more distant (d&sun;~6kpc) than recently reported in the literature. The age estimate for such a young object is crucial for the distance estimate. The high reddening of these two clusters relative to predictions from the diffuse interstellar medium at their distances is due to discrete intervening clouds. (2 data files).

We present new observations of Sextans and Leo I dwarf galaxies, that provide new insight on thei... more We present new observations of Sextans and Leo I dwarf galaxies, that provide new insight on their stellar populations. The large sample of stars measured in Sextans allowed us to obtain a reliable estimate of the metal content of this galaxy, to study the population spatial gradients, and to investigate the nature of the large number of blue stragglers. In Leo I, we discovered a significant population of RR Lyrae variables. The analysis of the pulsational properties of the detected variables suggests that this galaxy is an Oosterhoff intermediate object, similar to the LMC and to other dwarf galaxies in the Local Group.

Recent results on the detection of substructure in dwarf spheroidal galaxies are discussed. In mo... more Recent results on the detection of substructure in dwarf spheroidal galaxies are discussed. In most cases they show that, when a galaxy experiences multiple SF episodes, the intermediate age population is more centrally concentrated than the old population, and that the recent SF is even more concentrated towards the central regions. Moreover, it appears that the spatial distribution of stars becomes more and more irregular as younger and younger subpopulations are considered. We illustrate how wide-area observations, allowing a substantial coverage of dwarf spheroidals (in particular the satellites of the Milky Way), has provided evidence for cosmologically old populations in every dSph galaxy. All these results are placed in the broader scenario of population gradients in nearby dwarf galaxies of different morphological types.

Halo and Disk-like Components in Nearby Dwarf Galaxies

New deep observations at the ESO VLT and NTT were used to study the spatial distribution of stell... more New deep observations at the ESO VLT and NTT were used to study the spatial distribution of stellar populations with different ages in three distant Local Group dwarf galaxies. In all of them, recently formed stars are preferentially found in the central regions, embedded in a sheet of red, older stars. In the case of Antlia and SagDIG, the extended component is likely to be a disk rather than a spheroidal halo.

Proceedings of the International Astronomical Union

We present deep V, I photometry of the globular cluster Terzan 7, a probable member of the globul... more We present deep V, I photometry of the globular cluster Terzan 7, a probable member of the globular cluster system of the Sagittarius dwarf spheroidal galaxy. The metallicity, estimated from a new method based on analytic RGB fits, agrees with previous estimates based on color-magnitude diagrams ([Fe/H]= -0.9 ± 0.1 dex). This result confirms a discrepancy between photometric and spectroscopic determinations. Using both the horizontal and vertical methods to estimate relative ages, we confirm that the age of Terzan 7 is about 70% that of 47 Tuc. A rich population of blue stragglers is found, strongly concentrated toward the center of the cluster.

B and V photometry of the metal-rich bulge globular cluster NGC 6304

Astronomy and Astrophysics

We present B and V photometry of the bulge globular cluster NGC 6304. We derive a reddening E(B-V... more We present B and V photometry of the bulge globular cluster NGC 6304. We derive a reddening E(B-V) ~ 0.5 and a distance from the Sun dsun ~ 6 kpc. From the red giant branch morphology we estimate that the metallicity of NGC 6304 is intermediate between those of 47 Tuc and NGC 6528. The cluster is foreground to the bulk of the bulge population and the reddenings are comparable. Evidence of a hot stellar component belonging to the cluster is found. These hot stars could correspond to a blue extended horizontal branch and/or blue stragglers. Observations collected at the European Southern Observatory -- ESO, Chile, proposal no. 61.E-0335

Infrared Observations of Young Star Clusters

Star-Cluster Astrometry with Ground-Based Wide Field Imagers

We show the astrometric potential of the Wide Field Imager at the focus of the MPI-ESO 2.2m Teles... more We show the astrometric potential of the Wide Field Imager at the focus of the MPI-ESO 2.2m Telescope. Currently, we are able to measure the position of a well-exposed star with a precision of sim\simsim4 mas/frame in each coordinate (under 0.8 arcsec seeing conditions). We present some preliminary results here.

Abundances of red giants in NGC 6441 (Gratton+, 2006)

Equivalent widths for 5 giants members of the globular cluster NGC6441 (Table 3) and 7 field gian... more Equivalent widths for 5 giants members of the globular cluster NGC6441 (Table 3) and 7 field giants (Table 4) (3 data files).

Abundances of red giants in NGC 6388 (Carretta+, 2007)

Spectra for 13 RGB stars in NGC 6388 were obtained with UVES/FLAMES@VLT; based on radial velocity... more Spectra for 13 RGB stars in NGC 6388 were obtained with UVES/FLAMES@VLT; based on radial velocity, 7 of them resulted member stars. Abundances of Fe, O, Na, alpha-elements and heavier elements were derived using equivalent widths, model atmospheres and atmospheric parameters based on photometry. For each star we give identification, equatorial coordinates, VBIJK magnitudes, heliocentric radial velocity. For the 7 member stars we also present Teff, logg, [A/H], v_t, [Fe/H], [O/Fe], [Na/Fe], [Mg/Fe], [Al/Fe], [Si/Fe], [Ca/Fe], [Sc/Fe], [Ti/Fe], [V/Fe], [Cr/Fe], [Mn/Fe], [Co/Fe], [Ni/Fe], [Y/Fe], [Zr/Fe], [Ba/Fe], [La/Fe], [Ce/Fe], and [Eu/Fe]. We present here the EWs for all the above elements for the 7 member stars. (2 data files).

Abundances of red giants in NGC 6752 (Carretta+, 2007)

Spectra for 151 RGB stars in NGC 6752 were obtained with FLAMES@VLT using two gratings (HR11, HR1... more Spectra for 151 RGB stars in NGC 6752 were obtained with FLAMES@VLT using two gratings (HR11, HR13). Abundances of Fe, O, Na were derived using equivalent widths, model atmospheres and atmospheric parameters based on photometry. For each star we give identification, equatorial coordinates, VBJK magnitudes, S/N, heliocentric radial velocity for both gratings, Teff, logg, [A/H], vt, [Fe/H], [O/Fe], [Na/Fe]. Equivalent widths are given in tablea. (4 data files).

Evolved Stellar Populations in Nearby Galaxies: The Near-Infrared Perspective

We present near-infrared observations of the distant Milky Way satellite galaxies Leo I and Leo I... more We present near-infrared observations of the distant Milky Way satellite galaxies Leo I and Leo II, obtained with the new wide-field imager WFCAM at the UKIRT telescope as part of a study of evolved stars (Red Giant and Asymptotic Giant Branch stars) in Local Group dwarf spheroidal galaxies. Optical-infrared colors, which are more accurate metallicity indicators than optical or infrared colors alone, have been used to estimate the metallicity distribution of the red giant stars. Using near-infrared magnitudes and colors of luminous asymptotic giant branch (AGB) stars we have been able to discriminate carbon- and oxygen-rich AGB stars and derive their distributions in bolometric luminosity. In turn, the properties of AGB stars in different galactic environments will provide information on the star-formation histories of the parent galaxies.

JHK photometry of Fornax red giant branch (Gullieuszik+, 2007)

The catalogues of the upper red giant branch stars in Fornax dwarf Spheroidal galaxy are obtained... more The catalogues of the upper red giant branch stars in Fornax dwarf Spheroidal galaxy are obtained from ground-based SOFI@NTT observations. The shallow catalogue is obtained from a mosaic of 16 SOFI fields and covers an area of 18.5x18.5arcmin. The deep catalogue covers an area of 4.5x4.5arcmin. (2 data files).

Abundances of NGC 6121 red giants (Marino+, 2008)

Table 8 contains the equatorial coordinates, the atmospheric parameters measured on UVES spectra,... more Table 8 contains the equatorial coordinates, the atmospheric parameters measured on UVES spectra, UBVI_C photometry from WFI@2.2m telescope and infrared JHK photometry from 2MASS for the analysed stars. Table 9 contains the measured chemical abundances. (2 data files).