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S F Sanchez - One of the best experts on this subject based on the ideXlab platform.
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towards a new classification of galaxies principal component analysis of califa Circular Velocity curves
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: V Kalinova, Dario Colombo, Erik Rosolowsky, Rahul Kannan, L Galbany, R Garciabenito, R Gonzalez M Delgado, S F SanchezAbstract:We present a galaxy classification system for 238 (E1-Sdm) CALIFA (Calar Alto Legacy Integral Field Area) galaxies based on the shapes and amplitudes of their Circular Velocity curves (CVCs). We infer the CVCs from the de-projected surface brightness of the galaxies, after scaling by a constant mass-to-light ratio based on stellar dynamics - solving axisymmetric Jeans equations via fitting the second Velocity moment $V_{\mathrm{rms}}=\sqrt{V^2+\sigma^2}$ of the stellar kinematics. We use principal component analysis (PCA) applied to the CVC shapes to find characteristic features and use a $k$-means classifier to separate Circular curves into classes. This objective classification method identifies four different classes, which we name slow-rising (SR), flat (FL), round-peaked (RP) and sharp-peaked (SP) Circular curves. SR are typical for low-mass, late-type (Sb-Sdm), young, faint, metal-poor and disc-dominated galaxies. SP are typical for high-mass, early-type (E1-E7), old, bright, metal-rich and bulge-dominated galaxies. FL and RP appear presented by galaxies with intermediate mass, age, luminosity, metallicity, bulge-to-disk ratio and morphologies (E4-S0a, Sa-Sbc). The discrepancy mass factor, $f_d=1-M_{*}/M_{dyn}$, have the largest value for SR and SP classes ($\sim$ 74 per cent and $\sim$ 71 per cent, respectively) in contrast to the FL and RP classes (with $\sim$ 59 per cent and $\sim$ 61 per cent, respectively). Circular curve classification presents an alternative to typical morphological classification and appears more tightly linked to galaxy evolution.
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space density distribution of galaxies in the absolute magnitude rotation Velocity plane a volume complete tully fisher relation from califa stellar kinematics
Astronomy and Astrophysics, 2016Co-Authors: S Bekeraite, C J Walcher, J Falconbarroso, S F Sanchez, Mariya Lyubenova, Garcia B Lorenzo, K SpekkensAbstract:We measured the distribution in absolute magnitude – Circular Velocity space for a well-defined sample of 199 rotating galaxies of the Calar Alto Legacy Integral Field Area Survey (CALIFA) using their stellar kinematics. Our aim in this analysis is to avoid subjective selection criteria and to take volume and large-scale structure factors into account. Using stellar Velocity fields instead of gas emission line kinematics allows including rapidly rotating early-type galaxies. Our initial sample contains 277 galaxies with available stellar Velocity fields and growth curve r -band photometry. After rejecting 51 Velocity fields that could not be modelled because of the low number of bins, foreground contamination, or significant interaction, we performed Markov chain Monte Carlo modelling of the Velocity fields, from which we obtained the rotation curve and kinematic parameters and their realistic uncertainties. We performed an extinction correction and calculated the Circular Velocity v circ accounting for the pressure support of a given galaxy. The resulting galaxy distribution on the M r − v circ plane was then modelled as a mixture of two distinct populations, allowing robust and reproducible rejection of outliers, a significant fraction of which are slow rotators. The selection effects are understood well enough that we were able to correct for the incompleteness of the sample. The 199 galaxies were weighted by volume and large-scale structure factors, which enabled us to fit a volume-corrected Tully-Fisher relation (TFR). More importantly, we also provide the volume-corrected distribution of galaxies in the M r − v circ plane, which can be compared with cosmological simulations. The joint distribution of the luminosity and Circular Velocity space densities, representative over the range of −20 > M r > −22 mag, can place more stringent constraints on the galaxy formation and evolution scenarios than linear TFR fit parameters or the luminosity function alone.
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the califa and hipass Circular Velocity function for all morphological galaxy types
The Astrophysical Journal, 2016Co-Authors: S Bekeraitė, C J Walcher, L Wisotzki, Darren J Croton, J Falconbarroso, M Lyubenova, Danail Obreschkow, S F Sanchez, K SpekkensAbstract:The Velocity function (VF) is a fundamental observable statistic of the galaxy population that is similar to the luminosity function in importance, but much more difficult to measure. In this work we present the first directly measured Circular VF that is representative between 60 < ν_(circ) < 320 km s^(−1) for galaxies of all morphological types at a given rotation Velocity. For the low-mass galaxy population (60 < ν_(circ) < 170 km s^(−1), we use the HI Parkes All Sky Survey VF. For the massive galaxy population (170 < ν_(circ) < 320 km s^(−1), we use stellar Circular velocities from the Calar Alto Legacy Integral Field Area Survey (CALIFA). In earlier work we obtained the measurements of Circular Velocity at the 80% light radius for 226 galaxies and demonstrated that the CALIFA sample can produce volume-corrected galaxy distribution functions. The CALIFA VF includes homogeneous Velocity measurements of both late and early-type rotation-supported galaxies and has the crucial advantage of not missing gas-poor massive ellipticals that HI surveys are blind to. We show that both VFs can be combined in a seamless manner, as their ranges of validity overlap. The resulting observed VF is compared to VFs derived from cosmological simulations of the z = 0 galaxy population. We find that dark-matter-only simulations show a strong mismatch with the observed VF. Hydrodynamic simulations fare better, but still do not fully reproduce observations.
G Zhao - One of the best experts on this subject based on the ideXlab platform.
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the milky way s Circular Velocity curve and its constraint on the galactic mass with rr lyrae stars
The Astrophysical Journal, 2017Co-Authors: Iminhaji Ablimit, G ZhaoAbstract:We present a sample of 1148 ab-type RR Lyrae (RRLab) variables identified from Catalina Surveys Data Release 1, combined with SDSS DR8 and LAMOST DR4 spectral data. We first use a large sample of 860 Galactic halo RRLab stars and derive the Circular Velocity distributions for the stellar halo. With the precise distances and carefully determined radial velocities (the center-of-mass radial velocities) and by considering the pulsation of the RRLab stars in our sample, we can obtain a reliable and comparable stellar halo Circular Velocity curve. We follow two different prescriptions for the Velocity anisotropy parameter β in the Jeans equation to study the Circular Velocity curve and mass profile. Additionally, we test two different solar peculiar motions in our calculation. The best result we obtained with the adopted solar peculiar motion 1 of (U, V, W) = (11.1, 12, 7.2) km s−1 is that the enclosed mass of the Milky Way within 50 kpc is (3.75 ± 1.33) × 1011 M ⊙ based on β = 0 and the Circular Velocity 180 ± 31.92 (km s−1) at 50 kpc. This result is consistent with dynamical model results, and it is also comparable to the results of previous similar works.
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the milky way s Circular Velocity curve to 60 kpc and an estimate of the dark matter halo mass from the kinematics of 2400 sdss blue horizontal branch stars
The Astrophysical Journal, 2008Co-Authors: G Zhao, Timothy C Beers, Thorsten Naab, Matthias Steinmetz, F. C. Van Den Bosch, Eric F. Bell, Re P Fiorentin, Constance M Rockosi, Brian YannyAbstract:We derive new constraints on the mass of the Milky Way's dark matter halo, based on 2401 rigorously selected blue horizontal-branch halo stars from SDSS DR6. This sample enables construction of the full line-of-sight Velocity distribution at different galactocentric radii. To interpret these distributions, we compare them to matched mock observations drawn from two different cosmological galaxy formation simulations designed to resemble the Milky Way. This procedure results in an estimate of the Milky Way's Circular Velocity curve to ~60 kpc, which is found to be slightly falling from the adopted value of 220 km s?1 at the Sun's location, and implies -->M( Vcir(r) , derived in statistically independent bins, is found to be consistent with the expectations from an NFW dark matter halo with the established stellar mass components at its center. If we assume that an NFW halo profile of characteristic concentration holds, we can use the observations to estimate the virial mass of the Milky Way's dark matter halo, -->Mvir = 1.0+ 0.3?0.2 ? 1012 M?, which is lower than many previous estimates. We have checked that the particulars of the cosmological simulations are unlikely to introduce systematics larger than the statistical uncertainties. This estimate implies that nearly 40% of the baryons within the virial radius of the Milky Way's dark matter halo reside in the stellar components of our Galaxy. A value for -->Mvir of only ~ -->1 ? 1012 M? also (re)opens the question of whether all of the Milky Way's satellite galaxies are on bound orbits.
V Kalinova - One of the best experts on this subject based on the ideXlab platform.
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towards a new classification of galaxies principal component analysis of califa Circular Velocity curves
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: V Kalinova, Dario Colombo, Erik Rosolowsky, Rahul Kannan, L Galbany, R Garciabenito, R Gonzalez M Delgado, S F SanchezAbstract:We present a galaxy classification system for 238 (E1-Sdm) CALIFA (Calar Alto Legacy Integral Field Area) galaxies based on the shapes and amplitudes of their Circular Velocity curves (CVCs). We infer the CVCs from the de-projected surface brightness of the galaxies, after scaling by a constant mass-to-light ratio based on stellar dynamics - solving axisymmetric Jeans equations via fitting the second Velocity moment $V_{\mathrm{rms}}=\sqrt{V^2+\sigma^2}$ of the stellar kinematics. We use principal component analysis (PCA) applied to the CVC shapes to find characteristic features and use a $k$-means classifier to separate Circular curves into classes. This objective classification method identifies four different classes, which we name slow-rising (SR), flat (FL), round-peaked (RP) and sharp-peaked (SP) Circular curves. SR are typical for low-mass, late-type (Sb-Sdm), young, faint, metal-poor and disc-dominated galaxies. SP are typical for high-mass, early-type (E1-E7), old, bright, metal-rich and bulge-dominated galaxies. FL and RP appear presented by galaxies with intermediate mass, age, luminosity, metallicity, bulge-to-disk ratio and morphologies (E4-S0a, Sa-Sbc). The discrepancy mass factor, $f_d=1-M_{*}/M_{dyn}$, have the largest value for SR and SP classes ($\sim$ 74 per cent and $\sim$ 71 per cent, respectively) in contrast to the FL and RP classes (with $\sim$ 59 per cent and $\sim$ 61 per cent, respectively). Circular curve classification presents an alternative to typical morphological classification and appears more tightly linked to galaxy evolution.
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toward the dynamical classification of galaxies principal component analysis of sauron and califa Circular Velocity curves
arXiv: Astrophysics of Galaxies, 2015Co-Authors: V Kalinova, Dario Colombo, Erik Rosolowsky, Rahul Kannan, L Galbany, R Garciabenito, Mariya Lyubenova, Jesus Falconbarroso, Ronald Lasker, Rosa Gonzalez M DelgadoAbstract:We present a dynamical classification system for galaxies based on the shapes of their Circular Velocity curves (CVCs). We derive the CVCs of 40 SAURON and 42 CALIFA galaxies across Hubble sequence via a full line-of-sight integration as provided by solutions of the axisymmetric Jeans equations. We use Principal Component Analysis (PCA) applied to the Circular curve shapes to find characteristic features and use a k-means classifier to separate Circular curves into classes. This objective classification method identifies four different classes, which we name Slow-Rising (SR), Flat (F), Sharp-Peaked (SP) and Round-Peaked (RP) Circular curves. SR-CVCs are mostly represented by late-type spiral galaxies (Scd-Sd) with no prominent spheroids in the central parts and slowly rising velocities; F-CVCs span almost all morphological types (E,S0,Sab,Sb-Sbc) with flat Velocity profiles at almost all radii; SP-CVCs are represented by early-type and early-type spiral galaxies (E,S0,Sb-Sbc) with prominent spheroids and sharp peaks in the central velocities. RP-CVCs are represented by only two morphological types (E,Sa-Sab) with prominent spheroids, but RP-CVCs have much rounder peaks in the central velocities than SP-CVCs. RP-CVCs are typical for high-mass galaxies, while SR-CVCs are found for low-mass galaxies. Intermediate-mass galaxies usually have F-CVCs and SP-CVCs. Circular curve classification presents an alternative to typical morphological classification and may be more tightly linked to galaxy evolution.
Timothy C Beers - One of the best experts on this subject based on the ideXlab platform.
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the milky way s Circular Velocity curve between 4 and 14 kpc from apogee data
The Astrophysical Journal, 2012Co-Authors: Jo Bovy, Carlos Allende Prieto, Timothy C Beers, Dmitry Bizyaev, Luiz N Da Costa, K Cunha, G Ebelke, Daniel J Eisenstein, Peter M FrinchaboyAbstract:We measure the Milky Way's rotation curve over the Galactocentric range 4 kpc R 14 kpc from the first year of data from the Apache Point Observatory Galactic Evolution Experiment. We model the line-of-sight velocities of 3365 stars in 14 fields with b = 0? between 30? ? l ? 210? out to distances of 10 kpc using an axisymmetric kinematical model that includes a correction for the asymmetric drift of the warm tracer population (? R 35 km s?1). We determine the local value of the Circular Velocity to be Vc (R 0) = 218 ? 6 km s?1 and find that the rotation curve is approximately flat with a local derivative between ?3.0 km s?1 kpc?1 and 0.4 km s?1 kpc?1. We also measure the Sun's position and Velocity in the Galactocentric rest frame, finding the distance to the Galactic center to be 8 kpc 99 % confidence. We find an offset between the Sun's rotational Velocity and the local Circular Velocity of 26 ? 3 km s?1, which is larger than the locally measured solar motion of 12 km s?1. This larger offset reconciles our value for Vc with recent claims that Vc 240 km s?1. Combining our results with other data, we find that the Milky Way's dark-halo mass within the virial radius is ~8 ? 1011 M ?.
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Rotation curve of the Milky Way
EPJ Web of Conferences, 2012Co-Authors: Oleksiy Golubov, Andreas Just, Timothy C BeersAbstract:We use SEGUE and Hipparcos data to restrict the behaviour of the rotation curve of the Milky Way in the solar neighbourhood. Then we construct a density model of the Milky Way which best reproduces the available observations of the rotation curve and is consistent with the density constraints in the solar neighbourhood. This equation assumes constancy of the shape of the Velocity ellipsoid, its alignment with the axes of spherical coordinate system, and an exponential disc with scalelength Rd and a constant thickness. Thus we find the Circular Velocity vc for our samples. We assume the local Circular Velocity vc� = 231km/s, the local standard of rest from (3), and the disc scalelength Rd = 2.5kpc. The resulting rotation curve is presented in the left panel of Fig. 1. SEGUE sample is plotted with purple line, GCS is separated in 5 colour bins, which are plotted with points of different colours. Mean rotational velocities without correction for asymmetric drift being implemented are plotted with dashed lines, the corrected Circular Velocity with solid lines. The consistency of the Circular Velocity for GCS colour bins with different mean velocities demonstrates viability of the adopted value of Rd and other our assumptions. The rotation curve for the SEGUE data appears to be essentially flat in the solar neighbourhood. At least, it obviously demonstrates no drastic dip between 8 and 10kpc, as it was assumed in (6).
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The Milky Way’s Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from the Kinematics of ~2400 SDSS Blue Horizontal-Branch Stars
The Astrophysical Journal, 2008Co-Authors: Gang Zhao, Timothy C Beers, P. Re Fiorentin, Thorsten Naab, Matthias Steinmetz, F. C. Van Den Bosch, Eric F. BellAbstract:We derive new constraints on the mass of the Milky Way's dark matter halo, based on 2401 rigorously selected blue horizontal-branch halo stars from SDSS DR6. This sample enables construction of the full line-of-sight Velocity distribution at different galactocentric radii. To interpret these distributions, we compare them to matched mock observations drawn from two different cosmological galaxy formation simulations designed to resemble the Milky Way. This procedure results in an estimate of the Milky Way's Circular Velocity curve to ~60 kpc, which is found to be slightly falling from the adopted value of 220 km s?1 at the Sun's location, and implies -->M( Vcir(r) , derived in statistically independent bins, is found to be consistent with the expectations from an NFW dark matter halo with the established stellar mass components at its center. If we assume that an NFW halo profile of characteristic concentration holds, we can use the observations to estimate the virial mass of the Milky Way's dark matter halo, -->Mvir = 1.0+ 0.3?0.2 ? 1012 M?, which is lower than many previous estimates. We have checked that the particulars of the cosmological simulations are unlikely to introduce systematics larger than the statistical uncertainties. This estimate implies that nearly 40% of the baryons within the virial radius of the Milky Way's dark matter halo reside in the stellar components of our Galaxy. A value for -->Mvir of only ~ -->1 ? 1012 M? also (re)opens the question of whether all of the Milky Way's satellite galaxies are on bound orbits.
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the milky way s Circular Velocity curve to 60 kpc and an estimate of the dark matter halo mass from the kinematics of 2400 sdss blue horizontal branch stars
The Astrophysical Journal, 2008Co-Authors: G Zhao, Timothy C Beers, Thorsten Naab, Matthias Steinmetz, F. C. Van Den Bosch, Eric F. Bell, Re P Fiorentin, Constance M Rockosi, Brian YannyAbstract:We derive new constraints on the mass of the Milky Way's dark matter halo, based on 2401 rigorously selected blue horizontal-branch halo stars from SDSS DR6. This sample enables construction of the full line-of-sight Velocity distribution at different galactocentric radii. To interpret these distributions, we compare them to matched mock observations drawn from two different cosmological galaxy formation simulations designed to resemble the Milky Way. This procedure results in an estimate of the Milky Way's Circular Velocity curve to ~60 kpc, which is found to be slightly falling from the adopted value of 220 km s?1 at the Sun's location, and implies -->M( Vcir(r) , derived in statistically independent bins, is found to be consistent with the expectations from an NFW dark matter halo with the established stellar mass components at its center. If we assume that an NFW halo profile of characteristic concentration holds, we can use the observations to estimate the virial mass of the Milky Way's dark matter halo, -->Mvir = 1.0+ 0.3?0.2 ? 1012 M?, which is lower than many previous estimates. We have checked that the particulars of the cosmological simulations are unlikely to introduce systematics larger than the statistical uncertainties. This estimate implies that nearly 40% of the baryons within the virial radius of the Milky Way's dark matter halo reside in the stellar components of our Galaxy. A value for -->Mvir of only ~ -->1 ? 1012 M? also (re)opens the question of whether all of the Milky Way's satellite galaxies are on bound orbits.
Brian Yanny - One of the best experts on this subject based on the ideXlab platform.
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the milky way s Circular Velocity curve to 60 kpc and an estimate of the dark matter halo mass from the kinematics of 2400 sdss blue horizontal branch stars
The Astrophysical Journal, 2008Co-Authors: G Zhao, Timothy C Beers, Thorsten Naab, Matthias Steinmetz, F. C. Van Den Bosch, Eric F. Bell, Re P Fiorentin, Constance M Rockosi, Brian YannyAbstract:We derive new constraints on the mass of the Milky Way's dark matter halo, based on 2401 rigorously selected blue horizontal-branch halo stars from SDSS DR6. This sample enables construction of the full line-of-sight Velocity distribution at different galactocentric radii. To interpret these distributions, we compare them to matched mock observations drawn from two different cosmological galaxy formation simulations designed to resemble the Milky Way. This procedure results in an estimate of the Milky Way's Circular Velocity curve to ~60 kpc, which is found to be slightly falling from the adopted value of 220 km s?1 at the Sun's location, and implies -->M( Vcir(r) , derived in statistically independent bins, is found to be consistent with the expectations from an NFW dark matter halo with the established stellar mass components at its center. If we assume that an NFW halo profile of characteristic concentration holds, we can use the observations to estimate the virial mass of the Milky Way's dark matter halo, -->Mvir = 1.0+ 0.3?0.2 ? 1012 M?, which is lower than many previous estimates. We have checked that the particulars of the cosmological simulations are unlikely to introduce systematics larger than the statistical uncertainties. This estimate implies that nearly 40% of the baryons within the virial radius of the Milky Way's dark matter halo reside in the stellar components of our Galaxy. A value for -->Mvir of only ~ -->1 ? 1012 M? also (re)opens the question of whether all of the Milky Way's satellite galaxies are on bound orbits.