25 research outputs found
The UV spectral window: new means to constrain the stellar populations of early-type galaxies
We discuss the possibilities of exploiting the UV spectral using the J-PAS survey to disentangle young contributions from apparently old galaxies. We show that the feasibility of determining such young stellar components in early-type galaxies at moderately high redshift
Kinematical Signatures of Disc Instabilities and Secular Evolution in the MUSE TIMER Survey
The MUSE TIMER Survey has obtained high signal and high spatial resolution
integral-field spectroscopy data of the inner kpc of 21 nearby
massive disc galaxies. This allows studies of the stellar kinematics of the
central regions of massive disc galaxies that are unprecedented in spatial
resolution. We confirm previous predictions from numerical and hydrodynamical
simulations of the effects of bars and inner bars on stellar and gaseous
kinematics, and also identify box/peanuts via kinematical signatures in mildly
and moderately inclined galaxies, including a box/peanut in a face-on inner
bar. In 20/21 galaxies we find inner discs and show that their properties are
fully consistent with the bar-driven secular evolution picture for their
formation. In addition, we show that these inner discs have, in the region
where they dominate, larger rotational support than the main galaxy disc, and
discuss how their stellar population properties can be used to estimate when in
cosmic history the main bar formed. Our results are compared with photometric
studies in the context of the nature of galaxy bulges and we show that inner
discs are identified in image decompositions as photometric bulges with
exponential profiles (i.e., S\'ersic indices near unity).Comment: 4 pages, 5 figures, to appear in Galactic Dynamics in the Era of
Large Surveys, M. Valluri & J. A. Sellwood (eds.
On the accretion of a new group of galaxies onto Virgo: III. The stellar population radial gradients of dEs
Using MUSE data, we investigate the radial gradients of stellar population
properties (namely age, [M/H], and the abundance ratio of elements
[/Fe]) for a sample of nine dwarf early-type (dE) galaxies with
log(M/M) 9.0 and an infall time onto the Virgo
cluster of 2-3Gyr ago. We followed a similar approach as in Bidaran et al.
(2022) to derive their stellar population properties and star formation
histories (SFHs) through fitting observed spectral indices and full spectral
fitting, respectively. We find that these nine dE galaxies have truncated
[Mg/Fe]vs.[Fe/H] profiles than equally-massive Virgo dE galaxies with longer
past infall times. Short profiles of three dE galaxies are the result of their
intense star formation which has been quenched long before their accretion onto
the Virgo cluster, possibly as a result of their group environment. In the
remaining six dE galaxies, profiles mainly trace a recent episode of star burst
within 0.4R which results in higher light-weighted [/Fe]
values. The latter SFH peak can be due to ram pressure exerted by the Virgo
cluster at the time of the accretion of the dE galaxies. Also, we show that
younger, more metal-rich and less -enhanced stellar populations
dominate their inner regions (i.e., < 0.4R) resulting in mainly flat
, negative and positive . We find that with increasing log() of dE
galaxies, and flatten, and the
latter correlation persists even after including early-type galaxies up to
log( 2.5), possibly due to the more extended star
formation activity in the inner regions of dEs, as opposed to more massive
early-type galaxies.Comment: 18 pages, 8 figures, accepted in MNRA
On the accretion of a new group of galaxies onto Virgo – III. The stellar population radial gradients of dEs
Using MUSE data, we investigate the radial gradients of stellar population properties (namely age, [M/H], and the abundance ratio of α elements [α/Fe]) for a sample of nine dwarf early-type (dE) galaxies with log(M/M) ∼ 9.0 and an infall time onto the Virgo cluster of 2–3 Gyr ago. We followed a similar approach as in Bidaran et al. to derive their stellar population properties and star formation histories (SFHs) through fitting observed spectral indices and full spectral fitting, respectively. We find that these nine dE galaxies have truncated [Mg/Fe] versus [Fe/H] profiles than equally massive Virgo dE galaxies with longer past infall times. Short profiles of three dE galaxies are the result of their intense star formation which has been quenched long before their accretion onto the Virgo cluster, possibly as a result of their group environment. In the remaining six dE galaxies, profilesmainly trace a recent episode of star burst within 0.4Re which results in higher light-weighted [α/Fe] values. The latter SFH peak can be due to ram pressure exerted by the Virgo cluster at the time of the accretion of the dE galaxies. Also, we show that younger, more metal-rich, and less α-enhanced stellar populations dominate their inner regions (i.e. < 0.4Re) resulting in mainly flat ∇age, negative ∇[M/H], and positive ∇[α/Fe]. We find that with increasing log(σ Re) of dE galaxies, ∇age and ∇[α/Fe] flatten, and the latter correlation persists even after including early-type galaxies up to log(σ Re ∼ 2.5), possibly due to the more extended star formation activity in the inner regions of dEs, as opposed to more massive early-type galaxies
Integral-field kinematics and stellar populations of early-type galaxies out to three half-light radii
Funding: STFC grant ST/K502339/1 during the course of this work (NFB), Leverhulme Trust Early Career Fellowship (AW).We observed twelve nearby HI -detected early-type galaxies (ETGs) of stellar mass ∼ 1010 M⊙ ≤ M* ≤1011 M⊙ with the Mitchell Integral-Field Spectrograph, reaching approximately three half-light radii in most cases. We extracted line-of-sight velocity distributions for the stellar and gaseous components. We find little evidence of transitions in the stellar kinematics of the galaxies in our sample beyond the central effective radius, with centrally fast-rotating galaxies remaining fast-rotating and centrally slow-rotating galaxies likewise remaining slow-rotating. This is consistent with these galaxies having not experienced late dry major mergers; however, several of our objects have ionised gas that is misaligned with respect to their stars,suggesting some kind of past interaction. We extract Lick index measurements of the commonly-used Hβ, Fe5015, Mg, b, Fe5270 and Fe5335 absorption features, and we find most galaxies to have flat Hβ gradients and negative Mg, b gradients. We measure gradients of age, metallicity and abundance ratio for our galaxies using spectral fitting, and for the majority of our galaxies find negative age and metallicity gradients. We also find the stellar mass-to-light ratios to decrease with radius for most of the galaxies in our sample. Our results are consistent with a view in which intermediate-mass ETGs experience mostly quiet evolutionary histories, but in which many have experienced some kind of gaseous interaction in recent times.PostprintPeer reviewe
The EDGE-CALIFA survey: validating stellar dynamical mass models with CO kinematics
Deriving circular velocities of galaxies from stellar kinematics can provide
an estimate of their total dynamical mass, provided a contribution from the
velocity dispersion of the stars is taken into account. Molecular gas (e.g.,
CO) on the other hand, is a dynamically cold tracer and hence acts as an
independent circular velocity estimate without needing such a correction. In
this paper we test the underlying assumptions of three commonly used dynamical
models, deriving circular velocities from stellar kinematics of 54 galaxies
(S0-Sd) that have observations of both stellar kinematics from the CALIFA
survey, and CO kinematics from the EDGE survey. We test the Asymmetric Drift
Correction (ADC) method, as well as Jeans, and Schwarzschild models. The three
methods each reproduce the CO circular velocity at 1Re to within 10%. All three
methods show larger scatter (up to 20%) in the inner regions (R < 0.4Re) which
may be due to an increasingly spherical mass distribution (which is not
captured by the thin disk assumption in ADC), or non-constant stellar M/L
ratios (for both the JAM and Schwarzschild models). This homogeneous analysis
of stellar and gaseous kinematics validates that all three models can recover
Mdyn at 1Re to better than 20%, but users should be mindful of scatter in the
inner regions where some assumptions may break down.Comment: 22 pages, 18 figures, Accepted for publication in MNRA
Looking into the faintEst WIth MUSE (LEWIS): on the nature of ultra-diffuse galaxies in the Hydra-I cluster.I. Project description and preliminary results
Looking into the faintEst WIth MUSE (LEWIS) is an ESO large observing
programme aimed at obtaining the first homogeneous integral-field spectroscopic
survey of 30 extremely low-surface brightness (LSB) galaxies in the Hydra I
cluster of galaxies, with MUSE at ESO-VLT. The majority of LSB galaxies in the
sample (22 in total) are ultra-diffuse galaxies (UDGs). The distribution of
systemic velocities Vsys ranges between 2317 km/s and 5198 km/s and is centred
on the mean velocity of Hydra I (Vsys = 3683 46 km/s). Considering the
mean velocity and the velocity dispersion of the cluster, 17 out of 20 targets
are confirmed cluster members. To assess the quality of the data and
demonstrate the feasibility of the science goals, we report the preliminary
results obtained for one of the sample galaxies, UDG11. For this target, we
derived the stellar kinematics, including the 2-dimensional maps of
line-of-sight velocity and velocity dispersion, constrained age and
metallicity, and studied the globular cluster (GC) population hosted by the
UDG. Results are compared with the available measurements for UDGs and dwarf
galaxies in literature. By fitting the stacked spectrum inside one effective
radius, we find that UDG11 has a velocity dispersion km/s,
it is old ( Gyr), metal-poor ([M/H]=-1.170.11 dex) and has a total
dynamical mass-to-light ratio M, comparable to those observed for
classical dwarf galaxies. The spatially resolved stellar kinematics maps
suggest that UDG11 does not show a significant velocity gradient along either
major or minor photometric axes. We find two GCs kinematically associated with
UDG11. The estimated total number of GCs in UDG11, corrected for the
spectroscopic completeness limit, is , which
corresponds to a GC specific frequency of .Comment: Accepted for publication in Astronomy and Astrophysic
The Mice at play in the CALIFA survey: A case study of a gas-rich major merger between first passage and coalescence
We present optical integral field spectroscopy (IFS) observations of the
Mice, a major merger between two massive (>10^11Msol) gas-rich spirals NGC4676A
and B, observed between first passage and final coalescence. The spectra
provide stellar and gas kinematics, ionised gas properties and stellar
population diagnostics, over the full optical extent of both galaxies. The Mice
provide a perfect case study highlighting the importance of IFS data for
improving our understanding of local galaxies. The impact of first passage on
the kinematics of the stars and gas has been significant, with strong bars
likely induced in both galaxies. The barred spiral NGC4676B exhibits a strong
twist in both its stellar and ionised gas disk. On the other hand, the impact
of the merger on the stellar populations has been minimal thus far: star
formation induced by the recent close passage has not contributed significantly
to the global star formation rate or stellar mass of the galaxies. Both
galaxies show bicones of high ionisation gas extending along their minor axes.
In NGC4676A the high gas velocity dispersion and Seyfert-like line ratios at
large scaleheight indicate a powerful outflow. Fast shocks extend to ~6.6kpc
above the disk plane. The measured ram pressure and mass outflow rate
(~8-20Msol/yr) are similar to superwinds from local ULIRGs, although NGC4676A
has only a moderate infrared luminosity of 3x10^10Lsol. Energy beyond that
provided by the mechanical energy of the starburst appears to be required to
drive the outflow. We compare the observations to mock kinematic and stellar
population maps from a merger simulation. The models show little enhancement in
star formation during and following first passage, in agreement with the
observations. We highlight areas where IFS data could help further constrain
the models.Comment: 23 pages, 13 figures, accepted to A&A. A version with a complete set
of high resolution figures is available here:
http://www-star.st-and.ac.uk/~vw8/resources/mice_v8_astroph.pd