41 research outputs found
The Stellar Mass Fundamental Plane: The virial relation and a very thin plane for slow-rotators
Early-type galaxies -- slow and fast rotating ellipticals (E-SRs and E-FRs)
and S0s/lenticulars -- define a Fundamental Plane (FP) in the space of
half-light radius , enclosed surface brightness and velocity
dispersion . Since and are distance-independent
measurements, the thickness of the FP is often expressed in terms of the
accuracy with which and can be used to estimate sizes .
We show that: 1) The thickness of the FP depends strongly on morphology. If the
sample only includes E-SRs, then the observed scatter in is ,
of which only is intrinsic. Removing galaxies with
further reduces the observed scatter to ( intrinsic). The observed scatter increases to the usually
quoted in the literature if E-FRs and S0s are added. If the FP is defined using
the eigenvectors of the covariance matrix of the observables, then the E-SRs
again define an exceptionally thin FP, with intrinsic scatter of only
orthogonal to the plane. 2) The structure within the FP is most easily
understood as arising from the fact that and are nearly
independent, whereas the and correlations are nearly
equal and opposite. 3) If the coefficients of the FP differ from those
associated with the virial theorem the plane is said to be `tilted'. If we
multiply by the global stellar mass-to-light ratio and we account
for non-homology across the population by using S\'ersic photometry, then the
resulting stellar mass FP is less tilted. Accounting self-consistently for
gradients will change the tilt. The tilt we currently see suggests that
the efficiency of turning baryons into stars increases and/or the dark matter
fraction decreases as stellar surface brightness increases.Comment: 13 pages, 9 figures, 3 tables, accepted for publication in MNRA
Galaxy properties as revealed by MaNGA. III. Kinematic profiles and stellar population gradients in S0s
This is the third paper of a series where we study the stellar population
gradients (SP; ages, metallicities, -element abundance ratios and
stellar initial mass functions) of early type galaxies (ETGs) at
from the MaNGA-DR15 survey. In this work we focus on the S0 population and
quantify how the SP varies across the population as well as with galactocentric
distance. We do this by measuring Lick indices and comparing them to stellar
population synthesis models. This requires spectra with high signal-to-noise
which we achieve by stacking in bins of luminosity (L) and central velocity
dispersion (). We find that: 1) There is a bimodality in the S0
population: S0s more massive than show stronger
velocity dispersion and age gradients (age and decrease outwards)
but little or no metallicity gradient, while the less massive ones present
relatively flat age and velocity dispersion profiles, but a significant
metallicity gradient (i.e. [M/H] decreases outwards). Above
the number of S0s drops sharply. These two mass scales
are also where global scaling relations of ETGs change slope. 2) S0s have
steeper velocity dispersion profiles than fast rotating elliptical galaxies
(E-FRs) of the same luminosity and velocity dispersion. The kinematic profiles
and stellar population gradients of E-FRs are both more similar to those of
slow rotating ellipticals (E-SRs) than to S0s, suggesting that E-FRs are not
simply S0s viewed face-on. 3) At fixed , more luminous S0s and E-FRs
are younger, more metal rich and less -enhanced. Evidently for these
galaxies, the usual statement that 'massive galaxies are older' is not true if
is held fixed.Comment: Accepted for publication in MNRAS. 15 pages, 20 figure
Euclid preparation:XXVI. the Euclid Morphology Challenge: Towards structural parameters for billions of galaxies
The various Euclid imaging surveys will become a reference for studies of galaxy morphology by delivering imaging over an unprecedented area of 15 000 square degrees with high spatial resolution. In order to understand the capabilities of measuring morphologies from Euclid-detected galaxies and to help implement measurements in the pipeline of the Organisational Unit MER of the Euclid Science Ground Segment, we have conducted the Euclid Morphology Challenge, which we present in two papers. While the companion paper focusses on the analysis of photometry, this paper assesses the accuracy of the parametric galaxy morphology measurements in imaging predicted from within the Euclid Wide Survey. We evaluate the performance of five state-of-the-art surface-brightness-fitting codes, DeepLeGATo, Galapagos-2, Morfometryka, ProFit and SourceXtractor++, on a sample of about 1.5 million simulated galaxies (350 000 above 5s) resembling reduced observations with the Euclid VIS and NIR instruments. The simulations include analytic Sérsic profiles with one and two components, as well as more realistic galaxies generated with neural networks. We find that, despite some code-specific differences, all methods tend to achieve reliable structural measurements (< 10% scatter on ideal Sérsic simulations) down to an apparent magnitude of about IE = 23 in one component and IE = 21 in two components, which correspond to a signal-to-noise ratio of approximately 1 and 5, respectively. We also show that when tested on non-analytic profiles, the results are typically degraded by a factor of 3, driven by systematics. We conclude that the official Euclid Data Releases will deliver robust structural parameters for at least 400 million galaxies in the Euclid Wide Survey by the end of the mission. We find that a key factor for explaining the different behaviour of the codes at the faint end is the set of adopted priors for the various structural parameters.</p
The half mass radius of MaNGA galaxies: Effect of IMF gradients
Gradients in the stellar populations (SP) of galaxies -- e.g., in age,
metallicity, stellar Initial Mass Function (IMF) -- can result in gradients in
the stellar mass to light ratio, . Such gradients imply that the
distribution of the stellar mass and light are different. For old SPs, e.g., in
early-type galaxies at , the gradients are weak if driven by
variations in age and metallicity, but significantly larger if driven by the
IMF. A gradient which has larger in the center increases the estimated
total stellar mass () and reduces the scale which contains half this mass
(), compared to when the gradient is ignored. For the IMF gradients
inferred from fitting MILES simple SP models to the H,
Fe, [MgFe] and TiO absorption lines measured in
spatially resolved spectra of early-type galaxies in the MaNGA survey, the
fractional change in can be significantly larger than that in ,
especially when the light is more centrally concentrated. The
correlation which results is offset by 0.3 dex to smaller sizes compared to
when these gradients are ignored. Comparisons with `quiescent' galaxies at
higher- must account for evolution in SP gradients (especially age and IMF)
and the light profile before drawing conclusions about how and
evolve. The implied merging between higher- and the present is less
contrived if at is closer to our IMF-driven gradient
calibration than to unity.Comment: 16 pages, 15 figures, accepted for publication in MNRA
A multi-band AGN-SFG classifier for extragalactic radio surveys using machine learning
Extragalactic radio continuum surveys play an increasingly more important
role in galaxy evolution and cosmology studies. While radio galaxies and radio
quasars dominate at the bright end, star-forming galaxies (SFGs) and
radio-quiet Active Galactic Nuclei (AGNs) are more common at fainter flux
densities. Our aim is to develop a machine learning classifier that can
efficiently and reliably separate AGNs and SFGs in radio continuum surveys. We
perform supervised classification of SFGs vs AGNs using the Light Gradient
Boosting Machine (LGBM) on three LOFAR Deep Fields (Lockman Hole, Bootes and
ELAIS-N1), which benefit from a wide range of high-quality multi-wavelength
data and classification labels derived from extensive spectral energy
distribution (SED) analyses. Our trained model has a precision of 0.92(0.01)
and a recall of 0.87(0.02) for SFGs. For AGNs, the model has slightly worse
performance, with a precision of 0.87(0.02) and recall of 0.78(0.02). These
results demonstrate that our trained model can successfully reproduce the
classification labels derived from detailed SED analysis. The model performance
decreases towards higher redshifts, mainly due to smaller training sample
sizes. To make the classifier more adaptable to other radio galaxy surveys, we
also investigate how our classifier performs with a poorer multi-wavelength
sampling of the SED. In particular, we find that the far-infrared (FIR) and
radio bands are of great importance. We also find that higher S/N in some
photometric bands leads to a significant boost in the model's performance. In
addition to using the 150 MHz radio data, our model can also be used with 1.4
GHz radio data. Converting 1.4 GHz to 150 MHz radio data reduces performance by
about 4% in precision and 3% in recall. The final trained model is publicly
available at https://github.com/Jesper-Karsten/MBASCComment: 14 pages 9 figures Accepted for publication in A&
Galaxy And Mass Assembly (GAMA): M-star-R-e relations of z=0 bulges, discs and spheroids
We perform automated bulge + disc decomposition on a sample of ~7500 galaxies from the Galaxy And Mass Assembly (GAMA) survey in the redshift range of 0.002<z<0.06 using SIGMA, a wrapper around GALFIT3. To achieve robust profile measurements we use a novel approach of repeatedly fitting the galaxies, varying the input parameters to sample a large fraction of the input parameter space. Using this method we reduce the catastrophic failure rate significantly and verify the confidence in the fit independently of \chi^2 Additionally, using the median of the final fitting values and the 16^{th}$ and 84^{th} percentile produces more realistic error estimates than those provided by GALFIT, which are known to be underestimated. We use the results of our decompositions to analyse the stellar mass - half-light radius relations of bulges, discs and spheroids. We further investigate the association of components with a parent disc or elliptical relation to provide definite z=0 disc and spheroid M-star-R-e} relations. We conclude by comparing our local disc and spheroid M-star-R-e} to simulated data from EAGLE and high redshift data from CANDELS-UDS. We show the potential of using the mass-size relation to study galaxy evolution in both cases but caution that for a fair comparison all data sets need to be processed and analysed in the same manner
Euclid preparation. XXVI. The Euclid Morphology Challenge: Towards structural parameters for billions of galaxies
The various Euclid imaging surveys will become a reference for studies of galaxy morphology by delivering imaging over an unprecedented area of 15 000 square degrees with high spatial resolution. In order to understand the capabilities of measuring morphologies from Euclid-detected galaxies and to help implement measurements in the pipeline of the Organisational Unit MER of the Euclid Science Ground Segment, we have conducted the Euclid Morphology Challenge, which we present in two papers. While the companion paper focusses on the analysis of photometry, this paper assesses the accuracy of the parametric galaxy morphology measurements in imaging predicted from within the Euclid Wide Survey. We evaluate the performance of five state-of-the-art surface-brightness-fitting codes, , , , and , on a sample of about 1.5 million simulated galaxies (350 000 above 5σ) resembling reduced observations with the Euclid VIS and NIR instruments. The simulations include analytic Sérsic profiles with one and two components, as well as more realistic galaxies generated with neural networks. We find that, despite some code-specific differences, all methods tend to achieve reliable structural measurements (< 10% scatter on ideal Sérsic simulations) down to an apparent magnitude of about I = 23 in one component and I = 21 in two components, which correspond to a signal-to-noise ratio of approximately 1 and 5, respectively. We also show that when tested on non-analytic profiles, the results are typically degraded by a factor of 3, driven by systematics. We conclude that the official Euclid Data Releases will deliver robust structural parameters for at least 400 million galaxies in the Euclid Wide Survey by the end of the mission. We find that a key factor for explaining the different behaviour of the codes at the faint end is the set of adopted priors for the various structural parameters
X-shooter Spectroscopy and HST Imaging of 15 Massive Quiescent Galaxies at z ≳ 2
We present a detailed analysis of a large sample of spectroscopically confirmed massive quiescent galaxies (MQGs; log(M*/M ⊙) ~ 11.5) at z ≳ 2. This sample comprises 15 galaxies selected in the COSMOS and UDS fields by their bright K-band magnitudes and followed up with Very Large Telescope (VLT) X-shooter spectroscopy and Hubble Space Telescope (HST)/WFC3 H_(F160W) imaging. These observations allow us to unambiguously confirm their redshifts, ascertain their quiescent nature and stellar ages, and reliably assess their internal kinematics and effective radii. We find that these galaxies are compact, consistent with the high-mass end of the stellar mass–size relation for quiescent galaxies at z = 2. Moreover, the distribution of the measured stellar velocity dispersions of the sample is consistent with the most massive local early-type galaxies from the MASSIVE Survey, showing that evolution in these galaxies is dominated by changes in size. The HST images reveal, as surprisingly high, that 40% of the sample has tidal features suggestive of mergers and companions in close proximity, including three galaxies experiencing ongoing major mergers. The absence of velocity dispersion evolution from z = 2 to 0, coupled with a doubling of the stellar mass, with a factor of 4 size increase and the observed disturbed stellar morphologies, supports dry minor mergers as the primary drivers of the evolution of the MQGs over the last 10 billion yr
Euclid preparation: XXVI. the Euclid Morphology Challenge: Towards structural parameters for billions of galaxies
The various Euclid imaging surveys will become a reference for studies of galaxy morphology by delivering imaging over an unprecedented area of 15 000 square degrees with high spatial resolution. In order to understand the capabilities of measuring morphologies from Euclid-detected galaxies and to help implement measurements in the pipeline of the Organisational Unit MER of the Euclid Science Ground Segment, we have conducted the Euclid Morphology Challenge, which we present in two papers. While the companion paper focusses on the analysis of photometry, this paper assesses the accuracy of the parametric galaxy morphology measurements in imaging predicted from within the Euclid Wide Survey. We evaluate the performance of five state-of-the-art surface-brightness-fitting codes, DeepLeGATo, Galapagos-2, Morfometryka, ProFit and SourceXtractor++, on a sample of about 1.5 million simulated galaxies (350 000 above 5σ) resembling reduced observations with the Euclid VIS and NIR instruments. The simulations include analytic Sérsic profiles with one and two components, as well as more realistic galaxies generated with neural networks. We find that, despite some code-specific differences, all methods tend to achieve reliable structural measurements (< 10% scatter on ideal Sérsic simulations) down to an apparent magnitude of about IE = 23 in one component and IE = 21 in two components, which correspond to a signal-to-noise ratio of approximately 1 and 5, respectively. We also show that when tested on non-analytic profiles, the results are typically degraded by a factor of 3, driven by systematics. We conclude that the official Euclid Data Releases will deliver robust structural parameters for at least 400 million galaxies in the Euclid Wide Survey by the end of the mission. We find that a key factor for explaining the different behaviour of the codes at the faint end is the set of adopted priors for the various structural parameters
Euclid preparation XXVI. The Euclid Morphology Challenge. Towards structural parameters for billions of galaxies
The various Euclid imaging surveys will become a reference for studies of
galaxy morphology by delivering imaging over an unprecedented area of 15 000
square degrees with high spatial resolution. In order to understand the
capabilities of measuring morphologies from Euclid-detected galaxies and to
help implement measurements in the pipeline, we have conducted the Euclid
Morphology Challenge, which we present in two papers. While the companion paper
by Merlin et al. focuses on the analysis of photometry, this paper assesses the
accuracy of the parametric galaxy morphology measurements in imaging predicted
from within the Euclid Wide Survey. We evaluate the performance of five
state-of-the-art surface-brightness-fitting codes DeepLeGATo, Galapagos-2,
Morfometryka, Profit and SourceXtractor++ on a sample of about 1.5 million
simulated galaxies resembling reduced observations with the Euclid VIS and NIR
instruments. The simulations include analytic S\'ersic profiles with one and
two components, as well as more realistic galaxies generated with neural
networks. We find that, despite some code-specific differences, all methods
tend to achieve reliable structural measurements (10% scatter on ideal S\'ersic
simulations) down to an apparent magnitude of about 23 in one component and 21
in two components, which correspond to a signal-to-noise ratio of approximately
1 and 5 respectively. We also show that when tested on non-analytic profiles,
the results are typically degraded by a factor of 3, driven by systematics. We
conclude that the Euclid official Data Releases will deliver robust structural
parameters for at least 400 million galaxies in the Euclid Wide Survey by the
end of the mission. We find that a key factor for explaining the different
behaviour of the codes at the faint end is the set of adopted priors for the
various structural parameters.Comment: Accepted by A&A. 30 pages, 23+6 figures, Euclid pre-launch key paper.
Companion paper: Euclid Collaboration XXV: Merlin et al. 2022 Minor
corrections after journal revie