N. Gruel

Luminous Compact Galaxies at Intermediate Redshifts: Progenitors of Bulges of Massive Spirals?

VLT spectra of 14 luminous compact galaxies (LCGs) reveal strong metallic absorption-line systems as well as narrow and intense emission lines. Their gas extinction is found to be large (AV ~ 1.5 mag), leading to an upward revision of their star formation rate (SFR) to an average value of ~40 M☉ yr-1. Large extinction values are also supported by the large rate of detection in one field observed by the Infrared Space Observatory (ISO). Gas metal abundances in LCGs have about half the solar value. LCG absorption spectra can be synthesized with a mix of a few gigayears old and relatively metal-rich (generally solar to oversolar values) stellar population and a younger stellar population (less than 5 × 108 yr) having a metal abundance similar to that of the gas. We argue that LCGs are the progenitors of present-day spiral bulges. LCGs have masses and light concentrations similar to those of present-day bulges. They could have been formed entirely during a period of a few gigayears prior to the epoch of their observations if the star formation has been sustained at the observed rate. As in present-day galactic bulges, LCG stars show a wide range of abundances. Thus, observing LCGs allows us to witness directly an important stage in the formation of a massive galaxy, the building of the bulge prior to that of the disk. The gas needed to feed the observed star formation is likely to be falling in from the outskirts of the galaxy, being tidally pulled out from interacting companion galaxies. An infall scenario naturally explains the gas metal abundance, which is generally lower than that of the older stellar component. At least for the strongest star-forming LCGs, there is clear imaging evidence for the presence of companions. Some LCGs also show evidence for the beginning of a disk formation. If the above scenario holds for most LCGs, we estimate that at least 20% of present-day spiral galaxies have formed the bulk of their stars at relatively recent epochs, during the last 8-9 Gyr, at redshifts less than ~1. Since they are heavily extincted, we predict their IR luminosities to be relatively large, around LIR = 1011 L☉, i.e., near or slightly below the luminosities of the galaxies detected by ISO in the same redshift range. Taking into account the integrated IR luminosity of the LCG galaxy population can lead to a significant upward revision of the cosmic SFR density in the redshift range from 0.5 to 1.

3D spectroscopy of local luminous compact blue galaxies: kinematics of NGC 7673

The kinematic properties of the ionized gas of local Luminous Compact Blue Galaxy (LCBG) NGC 7673 are presented using three dimensional data taken with the PPAK integral field unit at the 3.5-m telescope in the Centro Astronomico Hispano Aleman. Our data reveal an asymmetric rotating velocity field with a peak to peak difference of 60 km s −1 . The kinematic centre is found to be at the position of a central velocity width maximum (� = 54± 1 km s −1 ), which is consistent with the position of the luminosity-weighted centroid of the entire galaxy. The position angle of the minor rotation axis is 168 � as measured from the orientation of the velocity field contours. At least two decoupled kinematic components are found. The first one is compact and coincides with the position of the second most active star formation region (clump B). The second one is extended and does not have a clear optical counterpart. No evidence of active galactic nuclei activity or supernovae galactic winds powering any of these two components has been found. Our data, however, show evidence in support of a previously proposed minor merger scenario in which a dwarf galaxy, tentatively identified with clump B, is falling into NGC 7673. and triggers the starburst. Finally, it is shown that the dynamical mass of this galaxy may be severely underestimated when using the derived rotation curve or the integrated velocity width, under the assumption of virialization.

KINEMATIC PROPERTIES AND STELLAR POPULATIONS OF FAINT EARLY-TYPE GALAXIES. II. LINE-STRENGTH MEASUREMENTS OF CENTRAL COMA GALAXIES

We present line-strength measurements for 74 early-type galaxies in the core of the Coma cluster reaching down to velocity dispersions, sigma, of 30 km s(-1). The index-sigma relations for our sample, including galaxies with sigma < 100 km s(-1) (low-sigma), differ in shape depending on which index is used. We note two types of relations for the metallic indices: one showing a break in the slope around similar to 100 km s(-1) and another group with strong linear relations between an index and log s. We find no connection between the behavior of index-sigma relations with either alpha- or Fe-peak elements. However, we find indications that the relations are tighter for indices which do not depend on the microturbulent velocities of stellar atmospheres. We confirm previous results that low-sigma galaxies including dE/dS0s are on average younger, less metal rich, and have lower [alpha/Fe] in comparison with E/S0s. Our data show that these trends derived for high-sigma galaxies extend down to dE/dS0s. This is a factor of similar to 2 lower in sigma than previously published work. We confirm that the observed anticorrelation between age and metallicity for high-sigma galaxies is consistent with the effects of correlated errors. Low-sigma galaxies also show a similar relation between age and metallicity as a result of correlated errors. However, they are offset from this relationship so that, on average, they are less metal rich and younger than their high-sigma counterparts.

IRMOS: The near-infrared multi-object spectrograph for the TMT

We present an overview of the near-InfraRed Multi-Object Spectrograph (IRMOS) for the Thirty Meter Telescope, as developed under a Feasibility Study at the University of Florida and Herzberg Institute of Astrophysics. IRMOS incorporates a multi-object adaptive optics correction capability over a 5-arcminute field of regard on TMT. Up to 20 independently-selectable target fields-of-view with ~2-arcsec diameter can be accessed within this field simultaneously. IRMOS provides near-diffraction-limited integral field spectroscopy over the 0.8-2.5 μm bandpass at R~1,000-20,000 for each target field. We give a brief summary of the Design Reference science cases for IRMOS. We then present an overview of the IRMOS baseline instrument design.

Dwarf galaxies in the Coma cluster – I. Velocity dispersion measurements

We present the study of a large sample of early-type dwarf galaxies in the Coma cluster observed with DEIMOS on the Keck II to determine their internal velocity dispersion. We focus on a subsample of 41 member dwarf elliptical galaxies for which the velocity dispersion can be reliably measured, 26 of which were studied for the first time. The magnitude range of our sample is -21 < MR < -15 mag. This paper (Paper I) focuses on the measurement of the velocity dispersion and their error estimates. The measurements were performed using penalized pixel fitting (PPXF) and using the calcium triplet absorption lines.We use Monte Carlo bootstrapping to study various sources of uncertainty in our measurements, namely statistical uncertainty, template mismatch and other systematics.We find that the main source of uncertainty is the template mismatch effect whichis reduced by using templates with a range of spectral types. Combining our measurements with those from the literature, we study the Faber–Jackson relation (L ? sa) and find that the slope of the relation is a = 1.99 ± 0.14 for galaxies brighter than MR �-16 mag. A comprehensive analysis of the results combined with the photometric properties of these galaxies is reported in Paper II.

FISICA: the Florida image slicer for infrared cosmology and astrophysics

We report on the design and status of the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) - a fully-cryogenic all-reflective image-slicing integral field unit for the FLAMINGOS near-infrared spectrograph. Designed to accept input beams near f/15, FISICA with FLAMINGOS provides R~1300 spectra over a 16x33-arcsec field-of-view on the Cassegrain f/15 focus of the KPNO 4-meter telescope, or a 6x12-arcsec field-of-view on the Nasmyth or Bent Cassegrain foci of the Gran Telescopio Canarias 10.4-meter telescope. FISICA accomplishes this using three sets of “monolithic” powered mirror arrays, each with 22 mirrored surfaces cut into a single piece of aluminum. We review the optical and opto-mechanical design and fabrication of FISICA, as well as laboratory test results for FISICA integrated with the FLAMINGOS instrument. We also discuss plans for first-light observations on the KPNO 4-meter telescope in July 2004.

Wide Integral-Field Infrared Spectroscopy of the Bright [Fe II] Shell in the Young Supernova Remnant G11.2-0.3

We present the results of wide integral-field near-infrared (1.0–1.8 µm) spectroscopic observations of the southeastern shell of the young core-collapse supernova remnant (SNR) G11.2−0.3. We first construct [Fe II] 1.644 µm line images of three bright clumps from the obtained spectral image cubes and compare them with those of other transitions such as [Fe II] 1.257, [Fe II] 1.534 and He I 1.083 µm line images. This allows us to estimate the electron density (∼ 4,700–9,400 cm −3 ) and extinction (AV ∼ 16–20 mag) of the shell, including detailed two-dimensional distribution of the properties in the brightest clump, as well as the discovery of a faint high-velocity (∼ –440 km s −1 ) component in the clump. Our SNR shock model calculations estimate the preshock number density of ∼ 250–500 cm −3 and shock speed of ∼ 80–250 km s −1 in the [Fe II]-emitting region of the SNR. The comparison between the observed and modelled radial profiles of the line intensities and their ratios reveals that the shell is composed of multiple thin filaments which have been likely formed in episodic mass loss processes of a progenitor star. The discovery of the faint high-velocity component supports the interpretation that the southeastern shell of G11.2−0.3 is mainly composed of circumstellar material with contamination by supernova ejecta and also that its ejected material was expelled primarily in the southeast-northwest direction. Subject headings: ISM: individual objects (G11.2−0.3) — ISM: supernova remnants — infrared: ISM — shock waves

Three-dimensional spectroscopy of local luminous compact blue galaxies: kinematic maps of a sample of 22 objects

We use three-dimensional optical spectroscopy observations of a sample of 22 local luminous compact blue galaxies (LCBGs) to create kinematic maps. By means of these, we classify the kinematics of these galaxies into three different classes: rotating disc (RD), perturbed rotation (PR) and complex kinematics (CK). We find 48 per cent are RDs, 28 per cent are PRs and 24 per cent are CKs. RDs show rotational velocities that range between similar to 50 and similar to 200 km s(-1), and dynamical masses that range between similar to 1 x 10(9) and similar to 3 x 10(10) M(circle dot). We also address the following two fundamental questions through the study of the kinematic maps: (i) What processes are triggering the current starburst in LCBGs? We search our maps of the galaxy velocity fields for signatures of recent interactions and close companions that may be responsible for the enhanced star formation in our sample. We find that 5 per cent of objects show evidence of a recent major merger, 10 per cent of a minor merger and 45 per cent of a companion. This argues in favour of ongoing interactions with close companions as a mechanism for the enhanced star formation activity in these galaxies. (ii) What processes may eventually quench the current starbust in LCBGs? Velocity and velocity width maps, together with emission line ratio maps, can reveal signatures of active galactic nuclei (AGNs) activity or supernova (SN)-driven galactic winds that could halt the current burst. We find only 5 per cent of objects with clear evidence of AGN activity and 27 per cent with kinematics consistent with SN-driven galactic winds. Therefore, a different mechanism may be responsible for quenching the star formation in LCBGs. Finally, from our analysis, we find that the velocity widths of RDs, rather than accounting exclusively for the rotational nature of these objects, may account as well for other kinematic components and may not be good tracers of their dynamical masses.

Stellar velocity dispersion of Luminous Compact Galaxies at intermediate redshift

ABSTRACT We present the stellar velocity dispersion measurements for 5 Luminous CompactGalaxies(LCGs) atz=0.5-0.7.Thesegalaxiesarevigorouslyformingstarswith averageSFR ∼40 M ⊙ /yr. We find that their velocity dispersions range from ∼137 km/s to260 km/s, while their stellar masses range between 4×10 9 and 10 11 M ⊙ . If these LCGsevolve passively after this major burst of star formation, their masses and velocitydispersions, as well as their evolved colours and luminosities are most consistent withthe values characteristic of early-type spiral galaxies today.Key words: galaxies: starburst - galaxies: kinematics and dynamics. 1 INTRODUCTIONLuminous Compact Galaxies (Hammer et al. 2001) arestarbursts galaxies at intermediate redshifts mostly de-tected in both UV and IR wavelengths, characterised byhaving small effective radii (R e 600) spectrograph FORS1 andFORS2 on the VLT/Kuyen telescope. The spectra revealedsome strong absorption lines (Ca II K and H, G Band,Fe I, and Balmer lines) as well as narrow and intenseemission lines ([OII]λ3727˚A, [OIII] λλ4858,5007˚A˚A, Balmerlines). The spectro-photometric analysis of these galax-ies (Hammer et al. 2001, Gruel 2002) showed that theyare likely composed of three different stellar populations.The youngest population presents strong emission lines([OII]λ3727˚A Balmer lines), indicating present day activestar formation and sub-solar metallicity. A second stellarpopulation was formed within the last few hundred millionyears. It is characterised by a solar metallicity and the pres-ence of Balmer lines in absorption. The third stellar pop-ulation, older than 5 Gyr, exhibits solar metal abundancesand strong metallic absorption lines (Calcium, Iron lines, Gband, Titanium, etc.) (Gruel 2002).Almost all LCGs analysed by Hammer et al. (2001)have large extinction coefficients (A

Statistical Challenges in the Photometric Calibration for 21st Century Cosmology: The J-PAS case

The success of many cosmological surveys in the near future is highly grounded on the quality of their photometry. The Javalambre-PAU Astrophysical Survey (J-PAS) will image more than 8500 deg 2 of the Northern Sky Hemisphere in 54 narrow + 2 medium/broad optical bands plus Sloan u, g and r bands. The main goal of J-PAS is to provide the best constrains on the cosmological parameters before the arrival of projects like Euclid or LSST. To achieve this goal the uncertainty in photo-z cannot be larger than 0.3% for several millions of galaxies and this is highly dependent on the photometric accuracy. The photometric calibration of J-PAS will imply the intensive use of huge amounts of data and the use of statistical tools is unavoidable. Here, we present some of the key steps in the photometric calibration of J-PAS that will demand a suitable statistical approach.