Brzozowski Algorithm Is Generically Super-Polynomial Deterministic Automata

International audienceWe study the number of states of the minimal automaton of the mirror of a rational language recognized by a random deterministic automaton with n states. We prove that, for any d > 0, the probability that this number of states is greater than nd tends to 1 as n tends to infinity. As a consequence, the generic and average complexities of Brzozowski minimization algorithm are super-polynomial for the uniform distribution on deterministic automata

Large-scale study of the NGC 1399 globular cluster system in Fornax

We present a Washington C and Kron-Cousins R photometric study of the globular cluster system of NGC 1399, the central galaxy of the Fornax cluster. A large areal coverage of 1 square degree around NGC 1399 is achieved with three adjoining fields of the MOSAIC II Imager at the CTIO 4-m telescope. Working on such a large field, we can perform the first indicative determination of the total size of the NGC 1399 globular cluster system. The estimated angular extent, measured from the NGC 1399 centre and up to a limiting radius where the areal density of blue globular clusters falls to 30 per cent of the background level, is 45 +/- 5 arcmin, which corresponds to 220 - 275 kpc at the Fornax distance. The bimodal colour distribution of this globular cluster system, as well as the different radial distribution of blue and red clusters, up to these large distances from the parent galaxy, are confirmed. The azimuthal globular cluster distribution exhibits asymmetries that might be understood in terms of tidal stripping of globulars from NGC 1387, a nearby galaxy. The good agreement between the areal density profile of blue clusters and a projected dark-matter NFW density profile is emphasized.Comment: 9 pages, 9 figures. Accepted for publication in A&

Searching for star-forming dwarf galaxies in the Antlia cluster

The formation and evolution of dwarf galaxies in clusters need to be understood, and this requires large aperture telescopes. In this sense, we selected the Antlia cluster to continue our previous work in the Virgo, Fornax, and Hydra clusters and in the Local Volume (LV). Because of the scarce available literature data, we selected a small sample of five blue compact dwarf (BCD) candidates in Antlia for observation. Using the Gemini South and GMOS camera, we acquired the Halpha imaging needed to detect star-forming regions in this sample. With the long-slit spectroscopic data of the brightest seven knots detected in three BCD candidates, we derived their basic chemical properties. Using archival VISTA VHS survey images, we derived K_S magnitudes and surface brightness profile fits for the whole sample to assess basic physical properties. FS90-98, FS90-106, and FS90-147 are confirmed as BCDs and cluster members, based on their morphology, K_S surface photometry, oxygen abundance, and velocity redshift. FS90-155 and FS90-319 did not show any H{\alpha} emission, and they could not be confirmed as dwarf cluster star-forming galaxies. Based on our data, we studied some fundamental relations to compare star forming dwarfs (BCDs and dIs) in the LV and in the Virgo, Fornax, Hydra, and Antlia clusters. Star-forming dwarfs in nearby clusters appear to follow same fundamental relations in the near infrared with similar objects in the LV, specifically the size-luminosity and the metallicity-luminosity, while other more fundamental relations could not be checked in Antlia due to lack of data.Comment: Accepted for publication in A&A (early 2014

On the trapping of stars by a newborn stellar supercluster

Numerical experiments conducted by Fellhauer et al. (MNRAS, 372, 338, 2006) suggest that a supercluster may capture up to about 40 per cent of its mass from the galaxy where it belongs. Nevertheless, in those experiments the cluster was created making appear its mass out of nothing, rather than from mass already present in the galaxy. Here we use a thought experiment, plus a few simple computations, to show that the difference between the dynamical effects of these two scenarios (i.e., mass creation vs. mass concentration) is actually very important. We also present the results of new numerical experiments, simulating the formation of the cluster through mass concentration, that show that trapping depends critically on the process of cluster formation and that the amounts of gained mass are substantially smaller than those obtained from mass creation.Comment: 6 pages, 3 figures. Submitted to MNRA

The dark matter halo of NGC 1399 - CDM or MOND?

Central galaxies in galaxy clusters may be key discriminants in the competition between the cold dark matter (CDM) paradigm and modified Newtonian dynamics (MOND). We investigate the dark halo of NGC 1399, the central galaxy of the Fornax cluster, out to a galactocentric distance of 80 kpc. The data base consists of 656 radial velocities of globular clusters obtained with MXU/VLT and GMOS/Gemini, which is the largest sample so far for any galaxy. We performed a Jeans analysis for a non-rotating isotropic model. An NFW halo with the parameters r_s = 50 kpc and rho_s = 0.0065 M_sun/pc^3 provides a good description of our data, fitting well to the X-ray mass. More massive halos are also permitted that agree with the mass of the Fornax cluster as derived from galaxy velocities. We compare this halo with the expected MOND models under isotropy and find that additional dark matter on the order of the stellar mass is needed to get agreement. A fully radial infinite globular cluster system would be needed to change this conclusion. Regarding CDM, we cannot draw firm conclusions. To really constrain a cluster wide halo, more data covering a larger radius are necessary. The MOND result appears as a small-scale variant of the finding that MOND in galaxy clusters still needs dark matter.Comment: 4 pages, 2 figures, accepted for publication as a Letter in A&

Compact Stellar Systems around NGC 1399

We have obtained spectroscopic redshifts of colour-selected point sources in four wide area VLT-FLAMES fields around the Fornax Cluster giant elliptical galaxy NGC 1399, identifying as cluster members 30 previously unknown faint (-10.5<M_g'<-8.8) compact stellar systems (CSS), and improving redshift accuracy for 23 previously catalogued CSS. By amalgamating our results with CSS from previous 2dF observations and excluding CSS dynamically associated with prominent (non-dwarf) galaxies surrounding NGC 1399, we have isolated 80 `unbound' systems that are either part of NGC 1399's globular cluster (GC) system or intracluster GCs. For these unbound systems, we find (i) they are mostly located off the main stellar locus in colour-colour space; (ii) their projected distribution about NGC 1399 is anisotropic, following the Fornax Cluster galaxy distribution, and there is weak evidence for group rotation about NGC 1399; (iii) their completeness-adjusted radial surface density profile has a slope similar to that of NGC 1399's inner GC system; (iv) their mean heliocentric recessional velocity is between that of NGC 1399's inner GCs and that of the surrounding dwarf galaxies, but their velocity dispersion is significantly lower; (v) bright CSS (M_V<-11) are slightly redder than the fainter systems, suggesting they have higher metallicity; (vi) CSS show no significant trend in $g' - i'$ colour index with radial distance from NGC 1399.Comment: 13 pages (including supplementary table), 13 figures, 5 tables. Accepted for publication in MNRA

The ARCHIPELAGO Archaeological Isotope Database for the Japanese Islands

ARCHIPELAGO is an archaeological and historical database of land and sea food resources utilised in the Japanese Islands. Here we present a dataset of human bone and hair carbon and nitrogen stable isotopes measurements from Japanese archaeological sites covering the time span from the Upper Palaeolithic to the mid-nineteenth century. Reflecting the results of over 30 years of research, the dataset contains 1476 entries and covers the entire Japanese archipelago, although the data are more highly concentrated in coastal regions.(1) Overview Context - Spatial coverage (2) Methods Steps Sampling strategy Quality control Constrains (3) Dataset description (4) Bayesian modelling of direct human radiocarbon measurements (5) Reuse potentia

Kinematic properties of the field elliptical NGC7507

The dark matter (DM) halos of field elliptical galaxies have not been well-studied and their properties appear controversial in the literature. While some galaxies appear to be nearly devoid of DM, others show clear evidence of its presence. Furthermore, modified Newtonian dynamics (MOND), which has been found to have predictive power in the domain of disk galaxies, has not yet been investigated for isolated elliptical galaxies. We study the kinematics of the isolated elliptical NGC 7507, which has been claimed as a clear example of DM presence in early-type galaxies. We obtained major and minor axis long-slit spectroscopy of NGC 7507 using the Gemini South telescope and deep imaging in Kron-Cousins R and Washington C using the CTIO/MOSAIC camera. Mean velocities, velocity dispersion and higher order moments of the velocity distribution are measured out to ∼90′′. The galaxy, although almost circular, has significant rotation along the minor axis and a rapidly declining velocity dispersion along both axes. The velocity dispersion profile is modeled in the context of a spherical Jeans analysis. Models without DM provide an excellent representation of the data with a mass-to-light ratio (M/L) of 3.1 (R-band). The most massive Navarro-Frenk-White (NFW) halo the data allow has a virial mass of only 3.9 -2.1 +3.1×10 11 M ⊙, although the data are more consistent with models that have a slight radial anisotropy, which implies the galaxy has an even lower DM halo mass of 2.2 -1.2 +2.0×10 11 M ⊙. Modeling of the h 4 Gauss-Hermite coefficient is inconclusive but seems to be consistent with mild radial anisotropy. A cored logarithmic DM halo with parameters r 0⊙l = 7 kpc and v 0 = 100 km s -1 can also reproduce the observed velocity dispersion profile. The MOND predictions overestimate the velocity dispersion. In conclusion, we cannot easily reproduce the previous findings of a predominance of DM in NGC 7507 within a simple spherical model. DM may be present, but only in conjunction with a strong radial anisotropy, for which there are some indications.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Galaxy populations in the Antlia cluster. I. Photometric properties of early-type galaxies

We present the first colour-magnitude relation (CMR) of early-type galaxies in the central region of the Antlia cluster, obtained from CCD wide-field photometry in the Washington photometric system. Integrated (C -T1) colours, T1 magnitudes, and effective radii have been measured for 93 galaxies (i.e. the largest galaxies sample in the Washington system till now) from the FS90 catalogue (Ferguson & Sandage 1990). Membership of 37 objects can be confirmed through new radial velocities and data collected from the literature. The resulting colour-magnitude diagram shows that early-type FS90 galaxies that are spectroscopically confirmed Antlia members or that were considered as definite members by FS90, follow a well defined CMR (sigma_(C -T1) ~ 0.07 mag) that spans 9 magnitudes in brightness with no apparent change of slope. This relation is very tight for the whole magnitude range but S0 galaxies show a larger dispersion, apparently due to a separation of ellipticals and S0s. Antlia displays a slope of -13.6 in a T1 vs. (C -T1) diagram, in agreement with results for clusters like Fornax, Virgo, Perseus and Coma, which are dynamically different to Antlia. This fact might indicate that the build up of the CMR in cluster of galaxies is more related to galaxies internal processes than to the influence of the environment. Interpreting the CMR as a luminosity-metallicity relation of old stellar systems, the metallicities of the Antlia galaxies define a global relation down to Mv ~ -13. We also find, for early-type dwarfs, no clear relation between luminosity and effective radius, indicating a nearly constant mean effective radius of ~ 1 kpc. This value is also found in several samples of dwarf galaxies in Virgo and Coma.Comment: 13 pages, 6 figures. Accepted for publication in MNRA