We investigate the enhancement of star formation efficiency in galaxy interactions and mergers by numerical simulations several hundred collisions. All morphological types along Hubble sequence are considered initial conditions two colliding galaxies, with varying bulge-to-disk ratios gas mass fractions. Different orbits simulated, direct retrograde, according to relative energy impact parameter, resulting history is compared that occuring galaxies when they isolated. Our principal results...

To compare photometric properties of galaxies at different redshifts, the fluxes need to be corrected for changes effective rest-frame wavelengths filter bandpasses, called K-corrections. Usual approaches compute them are based on template fitting observed spectral energy distributions (SED) and, thus, require multicolour photometry. Here, we demonstrate that, in cases widely used optical and near-infrared (NIR) filters, K-corrections can precisely approximated as two-dimensional low-order...

We investigate the intensity enhancement and duration of starburst episodes triggered by major galaxy interactions mergers. analyze two large statistical datasets numerical simulations. These have been obtained using independent different techniques to model baryonic dark matter evolution that are extensively compared for first time. One is a Tree-SPH code, other one grid-based N-body sticky-particles code. show that, at low redshift, mergers in general trigger only moderate star formation...

We present the GalMer database, a library of galaxy merger simulations, made available to users through tools compatible with Virtual Observatory (VO) standards adapted specially for this theoretical database. To investigate physics formation hierarchical merging, it is necessary simulate interactions varying large number parameters: morphological types, mass ratios, orbital configurations, etc. On one side, these simulations have be run in cosmological context, able provide pairs, boundary...

Abstract We present RCSED, the value-added Reference Catalog of Spectral Energy Distributions galaxies, which contains homogenized spectrophotometric data for 800,299 low- and intermediate-redshift galaxies ( <?CDATA $0.007\lt z\lt 0.6$?> ) selected from Sloan Digital Sky Survey spectroscopic sample. Accessible Virtual Observatory (VO) complemented with detailed information on galaxy properties obtained state-of-the-art analysis, RCSED enables direct studies formation evolution over last 5...

The Andromeda galaxy (M31) is the nearest giant spiral to our own, which offers an opportunity study dynamical phenomena occurring in nuclear disks and bulges at high resolution explain star formation quenching evolution through collisions tides. Multi-wavelength data have revealed strong perturbations central kiloparsec (kpc) region of M31, with off-centered tilted disk ring, coinciding a dearth atomic molecular gas. Our goal understand origin these and, thus, we propose model that...

We have carried out a survey of the Andromeda galaxy for unresolved microlensing (pixel lensing). present subset four short timescale, high signal-to-noise candidates found by imposing severe selection criteria: source flux variation exceeds an magnitude star and full width at half maximum timescale is less than 25 days. Remarkably, in three cases, we been able to measure or strongly constrain Einstein crossing time event. One event, which lies projected on M 31 bulge, almost certainly due...

We present a detailed description of the wavelength, astrometric and photometric calibration plan for SITELLE, imaging Fourier transform spectrometer attached to Canada-France-Hawaii telescope, based on observations red (647 - 685 nm) data cube central region (11$' \times 11'$) Andromeda galaxy. The first application, presented in this paper, is radial-velocity catalogue (with uncertainties $\sim 2 6$ km/s) nearly 800 emission-line point-like sources, including $\sim$ 450 new discoveries....

POINT—AGAPE is an Anglo-French collaboration which employing the Isaac Newton Telescope (INT) to conduct a pixel-lensing survey towards M31. Pixel lensing technique permits detection of microlensing against unresolved stellar fields. The aims constrain population in M31, and also distribution nature massive compact halo objects (MACHOs) both M31 Galaxy. In this paper we investigate what can learn from observables about MACHO mass fractional contribution Galaxy for case spherically symmetric,...

We report the discovery of a short-duration microlensing candidate in northern field POINT-AGAPE pixel lensing survey toward M31. Almost certainly, source star has been identified on Hubble Space Telescope archival images, allowing us to infer an Einstein crossing time tE = 10.4 days, maximum magnification Amax ~ 18, and lens-source proper motion μrel > 0.3 μas day-1. The event projected separation 8' from center M31, beyond bulk stellar lens population. There are three plausible...

Mergers can be detected as double-peak narrow emission line galaxies but they are difficult to disentangle from disc rotations and gas outflows. We aim properly detect such distinguish the underlying mechanisms. Relying on RCSED, we developed an automated selection procedure found 5663 at z&lt;0.34 corresponding 0.8% of parent database. To characterise these galaxies, built a single-peak no-bias control sample (NBCS) with same redshift stellar mass distributions (DPS). These two samples...

The study of the gas kinematic in central 1.5 kpc × region M 31 has revealed several surprises. starting point this investigation was detection at IRAM-30 m telescope molecular with very large line splittings up to 260 km s-1 within beam (~40 pc). In region, which is known for its low content, we also detect an ionised outflow circumnuclear (within 75 pc from centre) extending whole area X-ray. Relying on atomic, ionised, and gas, account most observables a scenario that assumes few hundreds...

We present a method for generating virtual observations from smoothed-particle-hydrodynamics (SPH) simulations. This includes stellar population synthesis models and the reprocessing of starlight by dust to produce realistic galaxy images. apply this simulate merging two identical giant Sa galaxies. The merger remnant is an elliptical galaxy. concentrates gas content galaxies into nuclear region. that flows region refuels central black holes follow refuelling during semi-analytically. In...

We report the discovery of a microlensing candidate projected 2'54" from center M32, on side closest to M31. The blue color (R-I= 0.00 +/- 0.14) source argues strongly that it lies in disk M31, while proximity line sight M32 implies this galaxy is most likely host lens. If interpretation correct, would confirm previous arguments front estimate order one such event or less should be present POINT-AGAPE data base. more events are discovered direction dedicated experiment, they could used...

We report the first detection of CO in bulge M31. The 12CO (1−0) and (2−1) lines are both detected dust complex D395A/393/384, at 1.3 arcmin (∼0.35 kpc) from centre. From these data visual extinction data, we derive a luminosity to reddening ratio (and H2 column density ratio) quite similar that observed local Galactic clouds. line intensity points rotational temperature gas kinetic >10 K. molecular mass complex, inside 25-arcsec (100 pc) region, is 1.5×104 M⊙.

We present the AGAPE astrometric and photometric catalogue of 1579 variable stars in a field centred on M 31. This work is first survey devoted to bulge The R magnitudes objects colours suggest that our sample dominated by red long-period (LPV), with possible overlap Cepheid-like type II stars. Fits light curves sinusoids large fraction correspond periodic or semi-periodic periods longer than 100 days. Twelve nova candidates are identified. Correlations other catalogues 2 novae could be...

We analysed the light curves of a large sample long period variables in LMC from AGAPEROS catalogue. The (non)regularity change is discussed detail showing that majority cannot be described properly by single period. show semiregular and small amplitude variability do not necessarily correlate as has been assumed several previous studies. Using near-infrared data DENIS survey we with colours luminosities objects. These results are used to compare LPVs Galactic Bulge solar neighborhood.

We investigate, by means of numerical simulations, the possibility forming counter-rotating old stellar components major mergers between an elliptical and a spiral galaxy. show that counter-rotation can appear both in dissipative dissipationless retrograde mergers, it is mostly associated to presence disk component, which preserves part its initial spin. In turn, external regions two interacting galaxies acquire orbital angular momentum, due action tidal forces exerted on each galaxy companion.

With IRAM-30m/HERA, we have detected CO(2-1) gas complexes within 30 arcsec (~100 pc) from the center of M31 amounting to a minimum total mass 4.2 x 10^4 Msol (one third positions are detected). Averaging whole HERA field, shown that there is no additional undetected diffuse component. We show above detection associated with lying on far side as extinction observed in optical, but some emission present infra-red Spitzer maps. The kinematics complex. (1) velocity pattern mainly redshifted:...

Given their prominent role in galaxy evolution, it is of paramount importance to unveil interactions and merger events investigate the underlying mechanisms. The use high-resolution data makes easier identify merging systems, but can still be challenging when morphology does not show any clear galaxy-pair or gas bridge. Characterising origin puzzling kinematic features help reveal complicated systems. Here, we present a galaxy, MaNGA 1-114955, which highlighted superimposition two distinct...

The central kiloparsec region of the Andromeda galaxy is relatively gas poor, while interstellar medium appears to be concentrated in a ring-like structure at about 10 kpc radius. depletion has been attributed possible head-on collision 200 Myr ago, supported by existence an offset inner ring warm dust. We present new IRAM 30m radio telescope observations molecular region, and detection CO its isotopes $^{13}$CO(2-1) C$^{18}$O(2-1), together with dense tracers, HCN(1-0) HCO+(1-0). A...

Abstract Numerical simulations represent an essential instrument to understand the physical processes occurring in interacting and merging systems, giving insight into evolution of their morphological kinematical properties, star‐formation histories, metal enrichement, etc. After a inexhaustive description some phenomena related galaxy collisions, we present GalMer Project, computational effort aiming at studying statistically role that interactions play determining evolution. (© 2008...

Emission lines with a double-peak (DP) shape, detected in the centre of galaxies, have been extensively used past to identify peculiar kinematics such as dual active galactic nuclei, outflows or mergers. From large DP galaxy sample, connection minor merger galaxies ongoing star formation was suggested. To gain better understanding different mechanisms creating signature, we here explore synthetic SDSS spectroscopic observations computed from disc models and simulations. We show how signature...