The presence of enhanced ultraviolet (UV) emission in early-type galaxies, which are dominated by old stellar populations, has been a puzzle for more than 40 years. The observed UV flux plausibly contains contributions from both evolved stars (traditionally referred to as the 'UV upturn' phenomenon) and young stars. While the UV upturn is well-characterised observationally, a firm understanding of its origin still eludes us. Similarly, while recent results from GALEX and deep optical surveys strongly indicate the presence of small mass fractions of young stars across low and intermediate redshift, the exact mechanism (e.g. stellar mass loss, minor mergers) that drives this star formation is not fully understood. The role of active galactic nuclei in regulating the low-level star formation at late epochs also remains relatively unexplored in galaxy formation models.

We present detailed study of the physical properties of the molecular gas in a sample of 18 gas-rich early-type galaxies -ETGs- from the ATLAS3D sample. Our goal is to better understand the star formation processes occurring in those galaxies, starting in this work by determining the properties of their molecular star-forming gas. Such study has never been performed before for ETGs and open a new window for exploring the star formation processes in the Universe. We use here the 12CO(1-0, 2-1), 13CO(1-0, 2-1), HCN(1-0) and HCO+(1-0) transitions already obtained (Krips et al. 2010 and Crocker et al. 2012 and new detections of the 12CO(3-2) line that we present too (see Bayet et al. 2012, re-submitted). From this dataset, we derive the average H2 kinetic temperature, H2 volume density and column density of the emitting gas using a non-Local Thermodynamical Equilibrium theoretical approach. For most of the gas-rich ETGs included in our sample, the CO transitions can be reproduced by gas kinetic temperatures between 10-20 K, densities of 103−4 cm−3 and CO column densities of 1018–20 cm−2. Since the CO lines trace different physical conditions than those required to emit the HCN and HCO+ lines, they are treated separately. The physical parameters corresponding to the HCN and HCO+ gas component suffer from large uncertainties and have to be considered as indicative only. In this study, for the first time, we also compare the predicted CO spectral line energy distributions of our gas-rich ETGs and their gas properties with those of a sample of nearby well-studied disc galaxies. The gas excitation conditions in 12/18 early-type galaxies appear analogous to those in the center fo Milky Way, hence the star formation activity driving these conditions may be of a similar strength and nature. The conclusions drawn have to be nevertheless considered carefully since they are based only on a limited number of observations. We show from our models that the 12CO(6-5) line emission is particularly useful for improving these results.

Evolutionary scenarios suggest that several mechanisms (from inner secular evolution to accretion/merging) may transform galaxy members, driving groups from an active star forming phase to a more passive, typical of dense environments. We are investigating this transition in a nearby group sample, designed to cover a wide range of properties (see also Marino et al. (2010), Bettoni et al. (2011) and Marino et al. (2012)). We study two groups, USGC U268 and USGC U376 located in different regions of the Leo cloud, through a photometric and kinematic characterization of their member galaxies. We revisit the group membership, using results from recent red-shift surveys, and we investigate their substructures. U268, composed of 10 catalogued members and 11 new added members, has a small fraction (~24%) of early-type galaxies (ETGs). U376 has 16 plus 8 new added members, with ~38% of ETGs. We find the significant substructuring in both groups suggesting that they are likely accreting galaxies. U268 is located in a more loose environment than U376. For each member galaxy, broad band integrated and surface photometry have been obtained in far-UV (FUV) and near-UV (NUV) with GALEX, and in u, g, r, i, z (SDSS) bands. Hα imaging and 2D high resolution kinematical data have been obtained using PUMA Scanning Fabry-Perot interferometer at the 2.12 m telescope in San Pedro Mártir (Baja California, México). We improved the galaxy classification and we detected morphological and kinematical distortions that may be connected to either on-going and/or past interaction/accretion events or environmental induced secular evolution. U268 appears more active than U376, with a large fraction of galaxies showing interaction signatures (60% vs. 13%). The presence of bars among late-type galaxies is ~10% in U268 and 29% in U376. The cumulative distribution of (FUV - NUV) colors of galaxies in U268 is significantly different (bluer) than that of U376's galaxies. Most (80%) of the early-type members in U376 inhabits the red sequence, a large fraction of galaxies, of different morphological types, are located in the green valley, while the blue sequence is under-populated with respect to U268.

We study the effects of including binary star evolution in population synthesis models. We use the Hurley et al. (2002) code to compute binary star evolutionary tracks, and follow the procedure by Han et al. (2002), in particular, the two 2HeWD merger channel, to form EHB stars from a binary pair. We apply the resulting models to study UV excess ETGs.

We present new population synthesis models (Chung et al.2011) for quiescent early-type galaxies (ETGs) with UV-upturn phenomenon using relatively metal-poor and helium-enhanced subpopulations in the model. We find that the presence of helium-enhanced subpopulations in ETGs can naturally reproduce the strong UV-upturns observed in giant elliptical galaxies (Figure 1. left panel), without invoking unrealistically old ages (Park & Lee 1997). Our models with helium-enhanced subpopulations also predict that the well-known Burstein relation can be explained by the fraction of helium-enhanced subpopulation, the mean age, and the mean metallicity of the underlying stellar populations (Figure 1. right panel).

In around ≈25% of early-type galaxies (ETGs) UV emission from young stellar populations is present. Molecular gas reservoirs have been detected in these systems (e.g. Young et al. (2011), providing the fuel for this residual star-formation. The environment in which this molecular gas is found is quite different than that in spiral galaxies however, with harsher radiation fields, deeper potentials and high metallicity and alpha-element abundances. Here we report on one element of our multi-faceted programme to understand the similarities and differences between the gas reservoirs in spirals and ETGs. We use spatially resolved observations from the CARMA mm-wave interferometer to investigate the size of the molecular reservoirs in the the CO-rich ATLAS3D ETGs (survey described in Alatalo et al. 2012, submitted). We find that the molecular gas extent is smaller in absolute terms in ETGs than in late-type galaxies, but that the size distributions are similar once scaled by the galaxies optical/stellar characteristic scale-lengths (Fig 1, left). Amongst ETGs, we find that the extent of the molecular gas is independent of the kinematic misalignment, despite the many reasons why misaligned gas might have a smaller extent. The extent of the molecular gas does depend on environment, with Virgo cluster ETGs having less extended molecular gas reservoirs (Fig 1, right). Whatever the cause, this further emphases that cluster ETGs follow different evolutionary pathways from those in the field. Full details of this work will be presented in Davis et al. (2012), submitted.

Far-ultraviolet (FUV) excess is crucial to our understanding of early-type galaxies and it is widely believed that the FUV radiation originates mainly from hot subwarf stars. Hot subdwarf stars may form from binary interactions or from single star evolution. In the binary channel, a star near the tip of the first giant branch (FGB) may get its envelope removed by its companion via stable Roche lobe overflow or common envelope ejection, and then evolves to a hot subdwarf star (Han et al.2002, 2003, 2007). Such a process does not depend much on metallicity.

Recent studies from the Galaxy Evolution Explore (GALEX) ultraviolet (UV) data reveal that the recent star formation is more common in early-type galaxies (ETGs) that we used to believe (Jeong et al.2007). Here we used the unique GALEX UV data on existing SAURON IFU-studied galaxies and combined these two datasets (UV and IFU) to find where photometric anomalies occur. One of the highlights of our study is the work on the Fundamental Plane (FP). The tilt and scatter found in optical FPs have been an issue. From our sample of 34 ETGs, we found that most of the tilt and scatter are caused by the minority ETGs which have been forming stars recently at very low level (see figure 1). Using our UV FPs, we found a strong evidence for star formation history being the main source of the mystery (Jeong et al.2009).

We present GALEX ultraviolet (UV) emission results of star-formation in a small sample of nearby, gas-rich early-type galaxies. The first observational evidence of star-formation in this sample was presented by Leeuw et al.2008, using 350 μm continuum data. The measured far-infrared (far-IR) excess of these galaxies showed that the most likely and dominant heating source of the observed 350 μm continuum emission from dust is star-formation, that could have been triggered by an accretion or merger event. Consistent with starbursts that are less than 1 Gyr (e.g., Kaviraj 2010), the GALEX near-UV (NUV) minus SDSS r-band emission of the galaxies is < 5.5. The UV results corroborate those of mid-IR to radio data for the sample.

This study is part of a series devoted to the investigation of a large sample of brightest cluster galaxies (BCGs), their properties and the relationships between these and the properties of the host clusters. In this paper, we compare the stellar population properties derived from high signal-to-noise, optical long-slit spectra with the GALEX ultraviolet (UV) colour measurements for 36 nearby BCGs to understand the diversity in the most rapidly evolving feature in old stellar systems, the UV-upturn. We investigate: (1) the possible differences between the UV-upturn of BCGs and those of a control sample of ordinary ellipticals in the same mass range, as well as possible correlations between the UV-upturn and other general properties of the galaxies; (2) possible correlations between the UV-upturn and the properties of the host clusters; (3) recently proposed scenarios where helium-sedimentation in the cluster centre can produce an enhanced UV-upturn. We find systematic differences between the UV-colours of BCGs and ordinary ellipticals, but we do not find correlations between these colours and the properties of the host clusters. Furthermore, the observations do not support the predictions made by the helium-sedimentation model as an enhancer of the UV-upturn.

We investigate the resolved star formation properties of a sample of 45 massive galaxies (M* > 1011 M⊙) within a redshift range of 1.5 ⩽ z ⩽ 3 detected in the GOODS NICMOS Survey (Conselice et al. 2011), a HST H160-band imaging program. We derive the star formation rate as a function of radius using rest frame UV data from deep z850 ACS imaging. The star formation present at high redshift is then extrapolated to z = 0, and we examine the stellar mass produced in individual regions within each galaxy. We also construct new stellar mass profiles of the in situ stellar mass at high redshift from Sérsic fits to rest-frame optical, H160-band, data. We combine the two stellar mass profiles to produce an evolved stellar mass profile. We then fit a new Sérsic profile to the evolved profile, from which we examine what effect the resulting stellar mass distribution added via star formation has on the structure and size of each individual galaxy.

Local early-type galaxies (ETGs), despite typically being associated to old stellar populations and passive evolution, have been in some cases observed to present peculiarities in their stellar structure, like disks and shells (e.g., Kormendy et al.1997, Rix, Carollo & Freeman 1999). Moreover, it has been observed that ETGs with such tidal features may present UV emission (Rampazzo et al.2007, Salim & Rich 2010). These properties make them relevant constraints to galaxy formation models. We are analysing the structure of nearby ETGs observed in the Spitzer Survey of Stellar Structure in Galaxies (S4G; Sheth et al.2010), which comprises the largest mid-IR survey of galaxies in the local Universe. We perform a 2D GALFIT decomposition of the 3.6μm images of 146 ETGs and examine their residual images. We identify tidal features in 17% of these, suggesting that a non-negligible ETGs fraction may have experienced (after the formation of the bulk of their stellar budget) merger events that have left signatures (Canalizo et al.2007). For 6 of these peculiar ETGs, we also applied GALFIT decomposition to public GALEX/UV and SDSS/optical images. With measurements in multiple bands, we applied SED fitting techniques to estimate star formation rates (SFR) and stellar masses for the galaxies and their tidal features. We find that these 6 peculiar ETGs present masses in agreement with the population of non-peculiar ETGs. However, SFRs are higher than what has been measured for the average ETG population (Shapiro et al.2010, SDSS MPA-JHU catalog). Based on the Kaviraj (2010) relation, we find that for these peculiar ETGs the estimated age of the most recent star formation event is less than 3Gyrs. Despite this indication of recent star formation, we have not found evidence of prominent UV emission in the tidal features (Marino et al.2010). We are currently extending our work to the full sample of peculiar ETGs identified in our sample.

The ultraviolet (UV) color-color relation of early-type galaxies (ETGs) in the nearby universe (0.05 < z < 0.12) is re-examined with the latest GALEX GR6 and SDSS DR7 data. By drawing the FUV – NUV (as a measure of UV temperature) versus FUV – r (as a measure of UV amplitude) color-color diagram for the morphologically-cleaned, spectroscopically-cleaned sample of ~3700 quiescent ETGs, we find that the “old and dead“ ETGs consist of a well-defined sequence in UV colors, the “UV red sequence”, so that the stronger UV excess galaxies should have a harder UV spectral shape systematically. However, the observed UV spectral slope is too steep to be reproduced by the canonical models in which the UV flux is mainly controlled by age or metallicity parameters. The observed data support the helium enhancement scenario in which the UV spectral shape of UV upturn (FUV – NUV < 0.9; FUV – r ~ 6) galaxies may be governed by the minority population of helium-enhanced horizontal-branch (HB) stars.

Early-type galaxies (ETGs) are thought to be devoid of dust and star-formation, having formed most of their stars at early epochs. We present the detection of the dustiest ETGs in a large-area blind submillimetre survey with Herschel (H-ATLAS, Eales et al.2010), where the lack of pre-selection in other bands makes it the first unbiased survey for cold dust in ETGs. The parent sample of 1087 H-ATLAS galaxies in this study have a ⩾ 5σ detection at 250μm, a reliable optical counterpart to the submillimetre source (Smith et al.2011) and a spectroscopic redshift from the GAMA survey (Driver et al.2011). Additionally, we construct a control sample of 1052 optically selected galaxies undetected at 250μm and matched in stellar mass to the H-ATLAS parent sample to eliminate selection effects. ETGs were selected from both samples via visual classifications using SDSS images. Further details can be found in Rowlands et al. (2012). Physical parameters are derived for each galaxy using the multiwavelength spectral energy distribution (SED) fitting code of da Cunha, Charlot and Elbaz (2008), Smith et al.2012, using an energy balance argument. We investigate the differences between the dusty ETGs and the general ETG population, and find that the H-ATLAS ETGs are more than an order of magnitude dustier than the control ETGs. The mean dust mass of the 42 H-ATLAS ETGs is 5.5 × 107M⊙ (comparable to the dust mass of spirals in our sample), whereas the dust mass of the 233 control ETGs inferred from stacking at optical positions on the 250μm map is (0.8 - 4.0) × 106M⊙ for 25-15 K dust. The average star-formation rate of the H-ATLAS ETGs is 1.0 dex higher than that of control ETGs, and the mean r-band light-weighted age of the H-ATLAS ETGs is 1.8 Gyr younger than the control ETGs. The rest-frame NUV - r colours of the H-ATLAS ETGs are 1.0 magnitudes bluer than the control ETGs, and some ETGs may be transitioning from the blue cloud to the red sequence. Some H-ATLAS ETGs show signs of morphological disturbance and may have undergone recent rejuvenation of their ISM via gas and dust delivered by mergers. It is found that late-type stars cannot produce enough dust to account for that observed in the H-ATLAS ETGs. This indicates that either an external source of dust from mergers is required, a substantial amount of dust grain growth must occur in the ISM, or dust destruction by hot X-ray gas is less efficient than predicted.

We measured the UV-optical-near-IR spectral energy distributions (SEDs) of redshift z ~ 0.3-1.5 early-type galaxies (ETGs) with the Hubble Space Telescope (HST) Wide Field Camera 3 (Rutkowski et al.2012). We searched for young stellar populations and morphological signatures of the mechanisms driving recent star formation (RSF) in these ETGs in order to provide observational constraints on models of galaxy evolution.

We observed the inner filament of NGC 5128 (Centaurus A) with the Hubble Space Telescope Wide Field Camera 3 (WFC3), using the F225W, F657N and F814W filters. We find a young stellar population near the south-west tip of the filament. We constrain the ages of these stars to 1-3 Myrs. No further recent star formation is found along the filament.

We propose an updated explanation for the origin of the inner filament. It has been suggested Sutherland et al.1993 that radio jets can shock the surrounding gas, giving rise to the observed optical line emission. We argue that such shocks can naturally arise due to a weak cocoon-driven bow shock (rather than from the radio jet directly) propagating through the diffuse interstellar medium. We suggest such a shock has overrun a molecular cloud, triggering star formation in the dense molecular core. The outer, more diffuse parts of the cloud are then ablated and shock heated, giving rise to the observed optical line and X-ray emission.

The current use of Type Ia supernova (SN Ia) as standard candles is to measure the dark energy equation-of-state to better than 10%. However, we still lack a clear understanding of their progenitor systems. We analyze the host galaxies of type Ia Supernova (SN Ia) discovered by the ESSENCE survey using UV and optical data, as studying the environments of SN Ia is a great way to understand the progenitors. We developed a new method for determining the SED and rest-frame magnitudes of the host galaxies and we use empirical relations to derive stellar mass and star-formation rate (SFR) measurements of the host galaxies. We find a high rate of UV emission in our passive galaxies, suggesting current star-formation in these galaxies.

It has long been known that the majority of early-type galaxies contain warm ionized gas producing optical emission lines. These warm ionized gas are spatially extended to kpc scales. Their line ratios satisify the criteria of Low-ionization Nuclear Emission-line Regions (LINERs) on all major line-ratio diagnostic diagrams. However, their ionization mechanism has been hotly debated. Multiple ionization mechanisms can produce the same kind of line ratios, including photoionization by a central AGN, photoionization by hot evolved stars (e.g. post-AGB stars), collisional ionization by fast shocks, photoionization by hot X-ray emitting gas, and conductive heating or turbulent mixing. Therefore, determining the ionization mechanism requires other information.

Based on 187 galaxy clusters identified from the photometric redshifts of galaxies in the Cosmic Evolution Survey (COSMOS) field(Wen & Han 2011), cluster galaxies brighter than MV = -20.5 are classified into four categories according to their best-fitting templates of the spectral energy distributions (SEDs) provided by Ilbert et al. (2009): early-type (including elliptical and lenticular) galaxies (E+S0), spiral galaxies (S), irregular galaxies (Irr), and starbursts (SB). The fractions of these four SED types are presented as the functions of redshift in Figure 1. Fraction of each category varies remarkably with cluster redshift: fractions of normal galaxies (E+S0+S+Irr) tend to decrease with redshift, whilst the starburst proportion tends to increase with redshift. For the normal galaxies, there exists a sequence for the decreasing slopes of morphological fractions. Majority of the galaxies in high-redshift clusters (z > 1.0) are experiencing strong star-formation activities, which leads to a very high proportion of starburst.

The Joint Discussion 5 entitled "From Meteors and Meteorites to their Parent Bodies: Current Status and Future Developments" within the IAU GA 2012 was organized with the coordination of the IAU Division III Planetary Systems Sciences and the IAU Commission N. 22 Meteors, Meteorites & Interplanetary Dust, together with the supports by Divisions I Fundamental Astronomy, Division XII Union-Wide Activities, Commission 4 Ephemerides, Commission 6 Astronomical Telegrams, Commission 8 Astrometry, Commission 15 Physical Study of Comets & Minor Planets, and Commission 20 Positions & Motions of Minor Planets, Comets & Satellites.