49 research outputs found
Planetary Nebulae and their parent stellar populations. Tracing the mass assembly of M87 and Intracluster light in the Virgo cluster core
The diffuse extended outer regions of galaxies are hard to study because they
are faint, with typical surface brightness of 1% of the dark night sky. We can
tackle this problem by using resolved star tracers which remain visible at
large distances from the galaxy centres. This article describes the use of
Planetary Nebulae as tracers and the calibration of their properties as
indicators of the star formation history, mean age and metallicity of the
parent stars in the Milky Way and Local Group galaxies . We then report on the
results from a deep, extended, planetary nebulae survey in a 0.5 sqdeg region
centred on the brightest cluster galaxy NGC 4486 (M87) in the Virgo cluster
core, carried out with SuprimeCam@Subaru and FLAMES-GIRAFFE@VLT. Two PN
populations are identified out to 150 kpc distance from the centre of M87. One
population is associated with the M87 halo and the second one with the
intracluster light in the Virgo cluster core. They have different line-of-sight
velocity and spatial distributions, as well as different planetary nebulae
specific frequencies and luminosity functions. The intracluster planetary
nebulae in the surveyed region correspond to a luminosity of four times the
luminosity of the Large Magellanic Cloud. The M87 halo planetary nebulae trace
an older, more metal-rich, parent stellar population. A substructure detected
in the projected phase-space of the line-of-sight velocity vs. major axis
distance for the M87 halo planetary nebulae provides evidence for the recent
accretion event of a satellite galaxy with luminosity twice that of M33. The
satellite stars were tidally stripped about 1 Gyr ago, and reached apocenter at
a major axis distance of 60-90 kpc from the centre of M87. The M87 halo is
still growing significantly at the distances where the substructure is
detected.Comment: 8 pages, 3 figures, To appear in the proceedings of the IAU Symposium
317 "The General Assembly of Galaxy Halos: Structure, Origin and Evolution'',
A. Bragaglia, M. Arnaboldi, M. Rejkuba & D. Romano, ed
Where stellar halos coexist with intracluster light
The work presented in this thesis studies the role that accretion
events play in the evolution of galaxies in dense environments, such as
galaxy clusters. Cosmological simulations allow us to study in detail
the evolution of galaxies' halos in cluster environments and have shown
that the formation of extended halos around central cluster
galaxies and intracluster light (ICL) is closely correlated to the
morphological transformation of galaxies in clusters. However, the
extremely low surface brightness of these components makes it
difficult to gather observational constraints.
This thesis studies the light and stellar motion in the halo of the
giant elliptical galaxy M87 and its surrounding IC component at the
centre of the Virgo cluster. Virgo is the nearest (~Mpc away)
large scale structure, a young cluster characterised by both spatial
and kinematic substructures. M87 has one of the oldest stellar
populations in the local Universe and a stellar halo that contains
70\% of the galaxy light down to . Moreover, deep images of the Virgo cluster core have
revealed an extended network of tidal features suggesting that
accretion events characterise its mass assembly. Thus, M87 and its host
environment are prime targets to shed light on the hierarchical
assembly of structure in the Universe.
This work uses new Suprime-Cam@Subaru photometry and FLAMES@VLT
spectroscopy to study a area around
M87, in the transition region between galaxy halo and ICL. We use
planetary nebulas (PNs) as tracers, whose strong [OIII] 5007
\AA\ emission line makes them excellent photometric and kinematic
probes, also at large distances from the galaxy's centre.
The photometric analysis of the PN sample shows the superposition of
two stellar populations, both halo and ICL. This is confirmed by
spectroscopically detected PNs, whose velocity phase-space also
reveals that halo and ICL split into two different kinematic
components. They have very different spatial distributions and parent
stars, as indicated by the properties of the PN populations they are
associated with, such as the -parameter and the slope of the
planetary nebula luminosity function (PNLF).
In this thesis I give the observational proof that in Virgo
the central galaxy and the ICL both evolve through the
ongoing accretion of smaller systems. However, stellar halo and ICL
are dynamically distinct components with different velocity and
density distributions, and parent stellar populations. Whether or not
these conclusions are true for different galaxies in different Virgo
subclusters is still an open question and the topic of one of
my planned future studies
The Planetary Nebulae Luminosity Function and distances to Virgo, Hydra I and Coma clusters
The luminosity function of planetary nebulae populations in galaxies within
10-15 Mpc distance has a cut-off at bright magnitudes and a functional form
that is observed to be invariant in different galaxy morphological types. Thus
it is used as a secondary distance indicator in both early and late-type
galaxies. Recent deep surveys of planetary nebulae populations in brightest
cluster galaxies (BCGs) seem to indicate that their luminosity functions
deviate from those observed in the nearby galaxies. We discuss the evidence for
such deviations in Virgo, and indicate which physical mechanisms may alter the
evolution of a planetary nebula envelope and its central star in the halo of
BCGs. We then discuss preliminary results for distances for the Virgo, Hydra I
and Coma clusters based on the observed planetary nebulae luminosity functions.Comment: 5 pages, one figure. To appear on the Proceedings of the IAU Symp.
289 "Advancing the physics of cosmic distances
The outer regions of the giant Virgo galaxy M87. Kinematic separation of stellar halo and intracluster light
We present a spectroscopic study of 287 Planetary Nebulas (PNs) in a total
area of ~0.4 deg^2 around the BCG M87 in Virgo A. With these data we can
distinguish the stellar halo from the co-spatial intracluster light (ICL). PNs
were identified from their narrow and symmetric redshifted lambda 5007\4959
Angstrom [OIII] emission lines, and the absence of significant continuum. We
implement a robust technique to measure the halo velocity dispersion from the
projected phase-space to identify PNs associated with the M87 halo and ICL. The
velocity distribution of the spectroscopically confirmed PNs is bimodal,
containing a narrow component centred on the systemic velocity of the BCG and
an off-centred broader component, that we identify as halo and ICL,
respectively. Halo and ICPN have different spatial distributions: the halo PNs
follow the galaxy's light, whereas the ICPNs are characterised by a shallower
power-law profile. The composite PN number density profile shows the
superposition of different PN populations associated with the M87 halo and the
ICL, characterised by different PN alpha-parameters, the ICL contributing ~3
times more PNs per unit light. Down to m_5007=28.8, the M87 halo PN luminosity
function (PNLF) has a steeper slope towards faint magnitudes than the IC PNLF,
and both are steeper than the standard PNLF for the M31 bulge. Moreover, the IC
PNLF has a dip at ~1-1.5 mag fainter than the bright cutoff, reminiscent of the
PNLFs of systems with extended star formation history. The M87 halo and the
Virgo ICL are dynamically distinct components with different density profiles
and velocity distribution. The different alpha values and PNLF shapes of the
halo and ICL indicate distinct parent stellar populations, consistent with the
existence of a gradient towards bluer colours at large radii. These results
reflect the hierarchical build-up of the Virgo cluster.Comment: 16 pages, 13 figures, 3 tables, A&A, in pres
Where stellar halos coexist with intracluster light
The work presented in this thesis studies the role that accretion
events play in the evolution of galaxies in dense environments, such as
galaxy clusters. Cosmological simulations allow us to study in detail
the evolution of galaxies' halos in cluster environments and have shown
that the formation of extended halos around central cluster
galaxies and intracluster light (ICL) is closely correlated to the
morphological transformation of galaxies in clusters. However, the
extremely low surface brightness of these components makes it
difficult to gather observational constraints.
This thesis studies the light and stellar motion in the halo of the
giant elliptical galaxy M87 and its surrounding IC component at the
centre of the Virgo cluster. Virgo is the nearest (~Mpc away)
large scale structure, a young cluster characterised by both spatial
and kinematic substructures. M87 has one of the oldest stellar
populations in the local Universe and a stellar halo that contains
70\% of the galaxy light down to . Moreover, deep images of the Virgo cluster core have
revealed an extended network of tidal features suggesting that
accretion events characterise its mass assembly. Thus, M87 and its host
environment are prime targets to shed light on the hierarchical
assembly of structure in the Universe.
This work uses new Suprime-Cam@Subaru photometry and FLAMES@VLT
spectroscopy to study a area around
M87, in the transition region between galaxy halo and ICL. We use
planetary nebulas (PNs) as tracers, whose strong [OIII] 5007
\AA\ emission line makes them excellent photometric and kinematic
probes, also at large distances from the galaxy's centre.
The photometric analysis of the PN sample shows the superposition of
two stellar populations, both halo and ICL. This is confirmed by
spectroscopically detected PNs, whose velocity phase-space also
reveals that halo and ICL split into two different kinematic
components. They have very different spatial distributions and parent
stars, as indicated by the properties of the PN populations they are
associated with, such as the -parameter and the slope of the
planetary nebula luminosity function (PNLF).
In this thesis I give the observational proof that in Virgo
the central galaxy and the ICL both evolve through the
ongoing accretion of smaller systems. However, stellar halo and ICL
are dynamically distinct components with different velocity and
density distributions, and parent stellar populations. Whether or not
these conclusions are true for different galaxies in different Virgo
subclusters is still an open question and the topic of one of
my planned future studies
Metal line emission from galaxy haloes at z~1
We present a study of the metal-enriched halo gas, traced using MgII and
[OII] emission lines, in two large, blind galaxy surveys - the MUSE (Multi Unit
Spectroscopic Explorer) Analysis of Gas around Galaxies (MAGG) and the MUSE
Ultra Deep Field (MUDF). By stacking a sample of ~600 galaxies (stellar masses
M* ~10^{6-12} Msun), we characterize for the first time the average metal line
emission from a general population of galaxy haloes at 0.7 <= z <= 1.5. The
MgII and [OII] line emission extends farther out than the stellar continuum
emission, on average out to ~25 kpc and ~45 kpc, respectively, at a surface
brightness (SB) level of 10^{-20} erg/s/cm2/arcsec2. The radial profile of the
MgII SB is shallower than that of the [OII], suggesting that the resonant MgII
emission is affected by dust and radiative transfer effects. The [OII] to MgII
SB ratio is ~3 over ~20-40 kpc, also indicating a significant in situ origin of
the extended metal emission. The average SB profiles are intrinsically brighter
by a factor ~2-3 and more radially extended by a factor of ~1.3 at 1.0 < z <=
1.5 than at 0.7 <= z <= 1.0. The average extent of the metal emission also
increases independently with increasing stellar mass and in overdense group
environments. When considering individual detections, we find extended [OII]
emission up to ~50 kpc around ~30-40 percent of the group galaxies, and
extended (~30-40 kpc) MgII emission around two z~1 quasars in groups, which
could arise from outflows or environmental processes.Comment: 24 pages, 21 figures, 2 tables, accepted for publication in MNRA
The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation
WEAVE, the new wide-field, massively multiplexed spectroscopic survey
facility for the William Herschel Telescope, will see first light in late 2022.
WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a
nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini'
integral field units (IFUs), and a single large IFU. These fibre systems feed a
dual-beam spectrograph covering the wavelength range 366959\,nm at
, or two shorter ranges at . After summarising the
design and implementation of WEAVE and its data systems, we present the
organisation, science drivers and design of a five- to seven-year programme of
eight individual surveys to: (i) study our Galaxy's origins by completing
Gaia's phase-space information, providing metallicities to its limiting
magnitude for 3 million stars and detailed abundances for
million brighter field and open-cluster stars; (ii) survey million
Galactic-plane OBA stars, young stellar objects and nearby gas to understand
the evolution of young stars and their environments; (iii) perform an extensive
spectral survey of white dwarfs; (iv) survey
neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and
kinematics of stellar populations and ionised gas in cluster galaxies;
(vi) survey stellar populations and kinematics in field galaxies
at ; (vii) study the cosmic evolution of accretion
and star formation using million spectra of LOFAR-selected radio sources;
(viii) trace structures using intergalactic/circumgalactic gas at .
Finally, we describe the WEAVE Operational Rehearsals using the WEAVE
Simulator.Comment: 41 pages, 27 figures, accepted for publication by MNRA
The wide-field, multiplexed, spectroscopic facility WEAVE : survey design, overview, and simulated implementation
Funding for the WEAVE facility has been provided by UKRI STFC, the University of Oxford, NOVA, NWO, Instituto de Astrofísica de Canarias (IAC), the Isaac Newton Group partners (STFC, NWO, and Spain, led by the IAC), INAF, CNRS-INSU, the Observatoire de Paris, Région Île-de-France, CONCYT through INAOE, Konkoly Observatory (CSFK), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Lund University, the Leibniz Institute for Astrophysics Potsdam (AIP), the Swedish Research Council, the European Commission, and the University of Pennsylvania.WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366-959 nm at R ∼ 5000, or two shorter ranges at R ∼ 20,000. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for ∼ 3 million stars and detailed abundances for ∼ 1.5 million brighter field and open-cluster stars; (ii) survey ∼ 0.4 million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey ∼ 400 neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in z 1 million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at z > 2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.PostprintPeer reviewe
The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation
WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366−959\,nm at R∼5000, or two shorter ranges at R∼20000. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for ∼3 million stars and detailed abundances for ∼1.5 million brighter field and open-cluster stars; (ii) survey ∼0.4 million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey ∼400 neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in z1 million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at z>2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator