13 research outputs found
Implications for the origin of dwarf early-type galaxies: a detailed look at the isolated rotating dwarf early-type galaxy CG 611, with ramifications for the Fundamental Plane's (S_K)^2 kinematic scaling and the spin-ellipticity diagram
Selected from a sample of nine, isolated, dwarf early-type galaxies (ETGs)
having the same range of kinematic properties as dwarf ETGs in clusters, we use
CG 611 (LEDA 2108986) to address the Nature versus Nurture debate regarding the
formation of dwarf ETGs. The presence of faint disk structures and rotation
within some cluster dwarf ETGs has often been heralded as evidence that they
were once late-type spiral or dwarf irregular galaxies prior to experiencing a
cluster-induced transformation into an ETG. However, CG 611 also contains
significant stellar rotation (~20 km/s) over its inner half light radius,
R_(e,maj)=0.71 kpc, and its stellar structure and kinematics resemble those of
cluster ETGs. In addition to hosting a faint young nuclear spiral within a
possible intermediate-scale stellar disk, CG 611 has accreted an
intermediate-scale, counter-rotating gas disk. It is therefore apparent that
dwarf ETGs can be built by accretion events, as opposed to disk-stripping
scenarios. We go on to discuss how both dwarf and ordinary ETGs with
intermediate-scale disks, whether under (de)construction or not, are not fully
represented by the kinematic scaling S_0.5=sqrt{ 0.5(V_rot)^2 + sigma^2 }, and
we also introduce a modified spin-ellipticity diagram, lambda(R)-epsilon(R),
with the potential to track galaxies with such disks.Comment: 15 pages (includes 9 figures and an extensive 2+ page reference list
Evolution of the anti-truncated stellar profiles of S0 galaxies since in the SHARDS survey: I - Sample and Methods
The controversy about the origin of the structure of S0--E/S0 galaxies may be
due to the difficulty of comparing surface brightness profiles with different
depths, photometric corrections and PSF effects (almost always ignored). We aim
to quantify the properties of Type-III (anti-truncated) discs in a sample of S0
galaxies at 0.2<z<0.6. In this paper, we present the sample selection and
describe in detail the methods to robustly trace the structure in their
outskirts and correct for PSF effects. We have selected and classified a sample
of 150 quiescent galaxies at 0.2<z<0.6 in the GOODS-N field. We perform a
quantitative structural analysis of 44 S0-E/S0 galaxies. We corrected their
surface brightness profiles for PSF distortions and analysed the biases in the
structural and photometric parameters when the PSF correction is not applied.
Additionally, we have developed Elbow, an automatic statistical method to
determine whether a possible break is significant - or not - and its type and
made it publicly available. We found 14 anti-truncated S0-E/S0 galaxies in the
range 0.2<z<0.6 (~30% of the final sample). This fraction is similar to the
those reported in the local Universe. In our sample, ~25% of the Type-III
breaks observed in PSF-uncorrected profiles are artifacts, and their profiles
turn into a Type I after PSF correction. PSF effects also soften Type-II
profiles. We found that the profiles of Type-I S0 and E/S0 galaxies of our
sample are compatible with the inner profiles of the Type-III, in contrast with
the outer profiles. We have obtained the first robust and reliable sample of 14
anti-truncated S0--E/S0 galaxies beyond the local Universe, in the range
0.2<z<0.6. PSF effects significantly affect the shape of the surface brightness
profiles in galaxy discs even in the case of the narrow PSF of HST/ACS images,
so future studies on the subject should make an effort to correct them.Comment: Accepted for publishing in Astronomy & Astrophysics. 75 pages, 57
figure
Evolution of the anti-truncated stellar profiles of SO galaxies since z=0.6 in the SHARDS survey II. Structural and photometric evolution
Context. Anti-truncated lenticular galaxies (Type-III S0s) present tight scaling relations between their surface brightness photometric and structural parameters. Although several evolutionary models have been proposed for the formation of these structures, the observations of Type-III S0 galaxies are usually limited to the local Universe. Aims. We aim to compare the properties of Type-III discs in a sample of S0 galaxies at 0.2 < z < 0.6with those of the local Universe. In this paper, we study the evolution of the photometric and structural scaling relations measured in the rest-frame R-band with z and the possible differences between the rest-frame (B - R) colours of the inner and outer disc profiles. Methods. We make use of a sample of 14 Type-III E/ S0-S0 galaxies at 0.2 < z < 0 : 6 from the GOODS-N field identified and characterised in a previous paper. We study whether or not the correlations found in local Type-III S0 galaxies were present similar to 6 Gyr ago. We analyse the distribution of the surface brightness characteristic parameters (R-break, mu(break), h(i), h(o), mu(0;) i and mu(0; o)) as a function of the stellar mass and look to see if there is a significant change with z. We also derive their rest-frame (B - R) colour profiles. Finally, we compare these results with the predictions from a grid of SSP models. Results. We find that the inner and outer scale-lengths of Type-III S0 galaxies at 0.4 < z < 0.6follow compatible trends and scaling relations with those observed in local S0 galaxies as a function of the break radius, R-break. We do not detect any significant differences between the location of R-break between z similar to 0.6 and z similar to 0 for a fixed stellar mass of the object, whereas the surface brightness at the break radius mu(break) is similar to 1.5 mag arcsec 2 dimmer in the local Universe than at z similar to 0.6 for a fixed stellar mass. We find no significant differences in the (B - R) colour between the inner and outer profiles of the Type-III S0 galaxies at 0.2 < z < 0.6. Conclusions. In contrast to Type-II (down-bending) profiles, the anti-truncated surface brightness profiles of S0 galaxies present compatible R-break values and scaling relations during the last 6 Gyr. This result and the similarity of the colours of the inner and outer discs point to a highly scalable and stable formation process, probably more related to gravitational and dynamical processes than to the evolution of stellar populations
Does the intermediate-mass black hole in LEDA 87300 (RGG 118) follow the near-quadratic Mbh-Mspheroid relation?
The mass scaling relation between supermassive black holes and their host spheroids has previously been described by a quadratic or steeper relation at low masses (105 < Mbh/Mo âČ 107). How this extends into the realm of intermediate-mass black holes (102 < Mbh/Mo < 105) is not yet clear, although for the barred Sm galaxy LEDA 87300, Baldassare et al. recently reported a nominal virial mass of Mbh = 5 104 Mo residing in a "spheroid" of stellar mass equal to 6.3 108 Mo. We point out, for the first time, that LEDA 87300 therefore appears to reside on the near-quadratic Mbh-Msph,â relation. However, Baldassare et al. modeled the bulge and bar as the single spheroidal component of this galaxy. Here we perform a 3-component bulge+bar+disk decomposition and find a bulge luminosity which is 7.7 times fainter than the published "bulge" luminosity. After correcting for dust, we find that Mbulge = 0.9 108 Mo and Mbulge/Mdisk = 0.04 - which is now in accord with ratios typically found in Scd-Sm galaxies. We go on to discuss slight revisions to the stellar velocity dispersion (40 11 km s-1) and black hole mass () and show that LEDA 87300 remains consistent with the Mbh-Ï relation, and also the near-quadratic Mbh-Msph,â relation when using the reduced bulge mass. LEDA 87300 therefore offers the first support for the rapid but regulated (near-quadratic) growth of black holes, relative to their host bulge/spheroid, extending into the domain of intermediate-mass black holes
Quantifying the (X/peanut)-shaped structure of the Milky Way â new constraints on the bar geometry
Quantifying the (X/peanut)-shaped structure in edge-on disc galaxies: length, strength, and nested peanuts
Searching for intermediate-mass black holes in galaxies with low-luminosity AGN: a multiple-method approach
International audienceAims. This work is the first stage of a campaign to search for intermediate-mass black holes (IMBHs) in low-luminosity active galactic nuclei (LLAGN) and dwarf galaxies. An additional and equally important aim of this pilot study is to investigate the consistency between the predictions of several popular black hole scaling relations and the fundamental plane (FP) of black-hole activity (FP-BH).Methods. We used well established X-ray and radio luminosity relations in accreting black holes, along with the latest scaling relations between the mass of the central black hole (MBH) and the properties of its host spheroid, to predict MBH in seven LLAGN, that were previously reported to be in the IMBH regime. Namely, we used the recently re-evaluated MBHâMsph (Msph: spheroid absolute magnitude at 3.6âÎŒm) scaling relation for spiral galaxies, the MBHânsph (nsph: major axis SĂ©rsic index of the spheroid component) relation, the MBHâPA (PA: spiral pitch angle) relation, and a recently re-calibrated version of the FP-BH for weakly accreting BHs, to independently estimate MBH in all seven galaxies.Results. We find that all LLAGN in our list have low-mass central black holes with logâMBH/Mâ â 6.5 on average, but that they are, most likely, not IMBHs. All four methods used predicted consistent BH masses in the 1Ï range. Furthermore, we report that, in contrast to previous classification, galaxy NGC 4470 is bulge-less, and we also cast doubts on the AGN classification of NGC 3507.Conclusions. We find that our latest, state-of-the-art techniques for bulge magnitude & SĂ©rsic index computations and the most recent updates of the MBHâLsph, MBHânsph, and MBHâPA relations and the FP-BH produce consistent results in the low-mass regime. We thus establish a multiple-method approach for predicting BH masses in the regime where their spheres of gravitational influence cannot be spatially resolved. Our approach mitigates against outliers from any one relation and provides a more robust average prediction. We will use our new method to revisit more IMBH candidates in LLAGN