We present a study of globular clusters (GCs) and other small stellar systems (SSSs) in the field... more We present a study of globular clusters (GCs) and other small stellar systems (SSSs) in the field of NGC 3115, observed as part of the ongoing wide-field imaging survey VEGAS, carried out with the 2.6m VST telescope. We use deep g and i observations of NGC 3115, a well-studied lenticular galaxy with excellent scientific literature. This is fundamental for testing the methodologies, verifying the results, and probing the capabilities of the VEGAS-SSS. Leveraging the large field of view of VST allows us to carry out an accurate study of the distribution and properties of SSSs as a function of galactocentric distance, well beyond ∼ 20 galaxy effective radii, in a way not often possible. Our analysis of colours, magnitudes and sizes of SSS candidates confirms the results from the existing studies, some of which carried out with 8-10m class telescopes, and further extends them to previously unreached galactocentric distances, with comparable accuracy. In particular, we find a colour bimodality for the GC population and a de Vaucouleurs r 1/4 profile for the surface density of GCs as for the galaxy light profile. The radial colour gradient of blue and red GCs already found, e.g., by the SLUGGS survey with Subaru and Keck data, is further extended out to the largest galactocentric radii inspected, ∼ 65 kpc. In addition, the surface density profiles of blue and red GCs taken separately are well approximated by a r 1/4 density profile, with the fraction of blue GCs being slightly larger at larger radii. We do not find hints of a trend for the red GC subpopulation and for the GC turnover magnitude to vary with radius, but we observe a ∼ 0.2 mag difference in the turnover magnitude of the blue and red GCs subpopulations. Finally, inspecting SSS sizes and colours we obtained a list of ultracompact dwarf galaxies and GC candidates suitable for future spectroscopic follow-up.
Optical imaging of RX J105453.3+552102 was carried out at the 2.5m NOT telescope in March 2008. O... more Optical imaging of RX J105453.3+552102 was carried out at the 2.5m NOT telescope in March 2008. Optical deep images were used for studying the properties of the brightest group galaxy and for computing the photometric luminosity function of the group. We have also performed a detail dynamical analysis of the system based on redshift data for 116 galaxies. Combining galaxy
We search for diffuse light in the galaxy group HCG 44 in order to determine its luminosity and l... more We search for diffuse light in the galaxy group HCG 44 in order to determine its luminosity and luminosity fraction. Combining with literature data, we aim to constrain the dynamical status of Hickson compact groups.We use Intra Group planetary nebulae (IGPNe) as tracers of diffuse light. These are detected by the so-called on band-off band technique.We found 12 emission line objects in HCG 44, none of them associated with the galaxies of the group. The absence of PNe in the elliptical galaxy, NGC 3193, implies that this galaxy is located behind the group, leaving only three spiral galaxy members in HCG 44. 6/12 emission line objects are consistent with being IGPNe in HCG 44, but are also consistent with being Lyα background galaxies. Thus we derive an upper limit to the diffuse light fraction in HCG 44 of 4.7%, corresponding to 1.06×10 9 L ⊙,B and mean surface brightness of µ B = 30.04 mag arcsec −2 . We find a correlation between the fraction of elliptical galaxies and the amount of diffuse light in Hickson compact groups. Those with large fraction of diffuse light are those with large fractions in number and luminosity of E/S0 galaxies. This indicates that the diffuse light is mainly created in dynamical processes during the formation of bright elliptical galaxies in major mergers.We propose an evolutionary sequence for Hickson compact groups in which the amount of diffuse light increases with the dynamical evolution of the group.
We have observed emission line objects located in a 0.26 deg 2 field in the M96 (Leo) group, coin... more We have observed emission line objects located in a 0.26 deg 2 field in the M96 (Leo) group, coincident with the intergalactic HI cloud. The emission line objects were selected using the same procedure as used for the search for intracluster planetary nebulae in the Virgo cluster. 29 emission line objects were identified, with [OIII] filter magnitudes brighter than m5007 = 28. Their m5007 luminosity function has a bright cut-off ≃ 1.2 magnitude fainter than for the luminosity function of the planetary nebulae (PN) associated with the elliptical galaxies in the M96 group. Therefore the vast majority of these emission line objects are compatible with not being intragroup planetary nebulae at the Leo group distance of 10 Mpc. Spectroscopic follow-up of two emission line objects in this Leo field showed that indeed these do not have the [OIII] λ4959, λ5007Å doublet expected for a real PN. The brighter source is identified as a starburst object at redshift z = 3.128, because of a second emission in the near infrared, identified as FeII (λ2220Å). From these data we derive three main results: (i) from the absence of PN we can determine a more stringent upper limit to the surface brightness in any old stellar population associated with the Leo HI cloud at the surveyed position, µB, * < 32.8 mag arcsec −2 . (ii) This translates to an upper limit of 1.6% for the fraction of luminosity in a diffuse intragroup component in the densest 3 • × 2 • area of the Leo group, relative to the light in galaxies. (iii) Using this Leo field as a blank field, we derive an average fraction of 13.6% background emission line objects that enter in surveys of Virgo intracluster PN. This is in agreement with an earlier estimate (15%) obtained from the Ly break galaxy population at z = 3.13. The small fraction confirms the validity of the selection criteria for intracluster PN candidates in Virgo.
The spin coherence phenomena and the possibility of their observation in nanomagnetic insulators ... more The spin coherence phenomena and the possibility of their observation in nanomagnetic insulators attract more and more attention during last several years. Recently, it has been shown that in these systems in large transverse fields there can be a fairly narrow" coherence window" for phonon and nuclear spin-mediated decoherence. Can the spin dynamics in this" window" remain coherent in a crystal of nanomolecules with central molecular spins $\ vec {S} $ coupled to each other via dipole-dipole interactions? ...
Monthly Notices of the Royal Astronomical Society, 2014
STEP (the SMC in Time: Evolution of a Prototype interacting late-type dwarf galaxy) is a Guarante... more STEP (the SMC in Time: Evolution of a Prototype interacting late-type dwarf galaxy) is a Guaranteed Time Observation survey being performed at the VST (the ESO VLT Survey Telescope). STEP will image an area of 74 deg 2 covering the main body of the Small Magellanic Cloud (32 deg 2 ), the Bridge that connects it to the Large Magellanic Cloud (30 deg 2 ) and a small part of the Magellanic Stream (2 deg 2 ). Our g, r, i, H α photometry is able to resolve individual stars down to magnitudes well below the main-sequence turnoff of the oldest populations. In this first paper we describe the observing strategy, the photometric techniques, and the upcoming data products of the survey. We also present preliminary results for the first two fields for which data acquisition is completed, including some detailed analysis of the two stellar clusters IC 1624 and NGC 419.
We present a study of globular clusters (GCs) and other small stellar systems (SSSs) in the field... more We present a study of globular clusters (GCs) and other small stellar systems (SSSs) in the field of NGC 3115, observed as part of the ongoing wide-field imaging survey VEGAS, carried out with the 2.6m VST telescope. We use deep g and i observations of NGC 3115, a well-studied lenticular galaxy with excellent scientific literature. This is fundamental for testing the methodologies, verifying the results, and probing the capabilities of the VEGAS-SSS. Leveraging the large field of view of VST allows us to carry out an accurate study of the distribution and properties of SSSs as a function of galactocentric distance, well beyond ∼ 20 galaxy effective radii, in a way not often possible. Our analysis of colours, magnitudes and sizes of SSS candidates confirms the results from the existing studies, some of which carried out with 8-10m class telescopes, and further extends them to previously unreached galactocentric distances, with comparable accuracy. In particular, we find a colour bimodality for the GC population and a de Vaucouleurs r 1/4 profile for the surface density of GCs as for the galaxy light profile. The radial colour gradient of blue and red GCs already found, e.g., by the SLUGGS survey with Subaru and Keck data, is further extended out to the largest galactocentric radii inspected, ∼ 65 kpc. In addition, the surface density profiles of blue and red GCs taken separately are well approximated by a r 1/4 density profile, with the fraction of blue GCs being slightly larger at larger radii. We do not find hints of a trend for the red GC subpopulation and for the GC turnover magnitude to vary with radius, but we observe a ∼ 0.2 mag difference in the turnover magnitude of the blue and red GCs subpopulations. Finally, inspecting SSS sizes and colours we obtained a list of ultracompact dwarf galaxies and GC candidates suitable for future spectroscopic follow-up.
Optical imaging of RX J105453.3+552102 was carried out at the 2.5m NOT telescope in March 2008. O... more Optical imaging of RX J105453.3+552102 was carried out at the 2.5m NOT telescope in March 2008. Optical deep images were used for studying the properties of the brightest group galaxy and for computing the photometric luminosity function of the group. We have also performed a detail dynamical analysis of the system based on redshift data for 116 galaxies. Combining galaxy
We search for diffuse light in the galaxy group HCG 44 in order to determine its luminosity and l... more We search for diffuse light in the galaxy group HCG 44 in order to determine its luminosity and luminosity fraction. Combining with literature data, we aim to constrain the dynamical status of Hickson compact groups.We use Intra Group planetary nebulae (IGPNe) as tracers of diffuse light. These are detected by the so-called on band-off band technique.We found 12 emission line objects in HCG 44, none of them associated with the galaxies of the group. The absence of PNe in the elliptical galaxy, NGC 3193, implies that this galaxy is located behind the group, leaving only three spiral galaxy members in HCG 44. 6/12 emission line objects are consistent with being IGPNe in HCG 44, but are also consistent with being Lyα background galaxies. Thus we derive an upper limit to the diffuse light fraction in HCG 44 of 4.7%, corresponding to 1.06×10 9 L ⊙,B and mean surface brightness of µ B = 30.04 mag arcsec −2 . We find a correlation between the fraction of elliptical galaxies and the amount of diffuse light in Hickson compact groups. Those with large fraction of diffuse light are those with large fractions in number and luminosity of E/S0 galaxies. This indicates that the diffuse light is mainly created in dynamical processes during the formation of bright elliptical galaxies in major mergers.We propose an evolutionary sequence for Hickson compact groups in which the amount of diffuse light increases with the dynamical evolution of the group.
We have observed emission line objects located in a 0.26 deg 2 field in the M96 (Leo) group, coin... more We have observed emission line objects located in a 0.26 deg 2 field in the M96 (Leo) group, coincident with the intergalactic HI cloud. The emission line objects were selected using the same procedure as used for the search for intracluster planetary nebulae in the Virgo cluster. 29 emission line objects were identified, with [OIII] filter magnitudes brighter than m5007 = 28. Their m5007 luminosity function has a bright cut-off ≃ 1.2 magnitude fainter than for the luminosity function of the planetary nebulae (PN) associated with the elliptical galaxies in the M96 group. Therefore the vast majority of these emission line objects are compatible with not being intragroup planetary nebulae at the Leo group distance of 10 Mpc. Spectroscopic follow-up of two emission line objects in this Leo field showed that indeed these do not have the [OIII] λ4959, λ5007Å doublet expected for a real PN. The brighter source is identified as a starburst object at redshift z = 3.128, because of a second emission in the near infrared, identified as FeII (λ2220Å). From these data we derive three main results: (i) from the absence of PN we can determine a more stringent upper limit to the surface brightness in any old stellar population associated with the Leo HI cloud at the surveyed position, µB, * < 32.8 mag arcsec −2 . (ii) This translates to an upper limit of 1.6% for the fraction of luminosity in a diffuse intragroup component in the densest 3 • × 2 • area of the Leo group, relative to the light in galaxies. (iii) Using this Leo field as a blank field, we derive an average fraction of 13.6% background emission line objects that enter in surveys of Virgo intracluster PN. This is in agreement with an earlier estimate (15%) obtained from the Ly break galaxy population at z = 3.13. The small fraction confirms the validity of the selection criteria for intracluster PN candidates in Virgo.
The spin coherence phenomena and the possibility of their observation in nanomagnetic insulators ... more The spin coherence phenomena and the possibility of their observation in nanomagnetic insulators attract more and more attention during last several years. Recently, it has been shown that in these systems in large transverse fields there can be a fairly narrow" coherence window" for phonon and nuclear spin-mediated decoherence. Can the spin dynamics in this" window" remain coherent in a crystal of nanomolecules with central molecular spins $\ vec {S} $ coupled to each other via dipole-dipole interactions? ...
Monthly Notices of the Royal Astronomical Society, 2014
STEP (the SMC in Time: Evolution of a Prototype interacting late-type dwarf galaxy) is a Guarante... more STEP (the SMC in Time: Evolution of a Prototype interacting late-type dwarf galaxy) is a Guaranteed Time Observation survey being performed at the VST (the ESO VLT Survey Telescope). STEP will image an area of 74 deg 2 covering the main body of the Small Magellanic Cloud (32 deg 2 ), the Bridge that connects it to the Large Magellanic Cloud (30 deg 2 ) and a small part of the Magellanic Stream (2 deg 2 ). Our g, r, i, H α photometry is able to resolve individual stars down to magnitudes well below the main-sequence turnoff of the oldest populations. In this first paper we describe the observing strategy, the photometric techniques, and the upcoming data products of the survey. We also present preliminary results for the first two fields for which data acquisition is completed, including some detailed analysis of the two stellar clusters IC 1624 and NGC 419.
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Papers by N. Napolitano