The measurement of Hα luminosity for large numbers of galaxies is important to investigate recent star formation history of galaxies. With SED fitting that includes emission line templates, we extract individual galaxy Hα luminosities from broad-band photometry. We compare Hα luminosity function with the result of a narrow-band survey, HiZELS, and find there are more luminous galaxies in Hα than previously reported. As a result, our derived star formation rate density at z ∼ 2.3 turns out to be 2.2 times higher than previous studies. Most of the offset in the results can be explained by missing Hα in the HiZELS photometric aperture and different methods for dust extinction correction.

I present an overview of the JWST Advanced Deep Extragalactic Survey (JADES), a joint program of the JWST/NIRCam and NIRSpec Guaranteed Time Observations (GTO) teams involving 950 hours of observation. We will target two well-studied fields with excellent supporting data (e.g., from HST-CANDELS): GOODS-North and South, including the Ultra Deep Field. The science goal of JADES is to chart galaxy evolution at z > 2, and potentially out to z > 10, using the rest-frame optical and near-IR though observations from ≍ 1–5μm. Multi-colour NIRCam imaging with 9 filters will enable photometric redshifts and the application of the Lyman break technique out to unprecedented distances. NIRSpec spectroscopy (with spectral resolving powers of R = 100, 1000 & 2700) will measure secure spectroscopic redshifts of the photometrically-selected population, as well as stellar continuum slopes in the UV rest-frame, and hence study the role of dust, stellar population age, and other effects. Measuring emission lines can constrain the dust extinction, star formation rates, metallicity, chemical abundances, ionization and excitation mechanism in high redshift galaxies. Coupling NIRCam and NIRSpec observations will determine stellar populations (age, star formation histories, abundances) of galaxies and provide the information to correct their broad-band spectral energy distribution for likely line contamination. Potentially we can search for signatures of Population III stars such as HeII. We can address the contribution of star-forming galaxies at z > 7 to reionization by determining the faint end slope of the luminosity function and investigating the escape fraction of ionizing photons by comparing the UV stellar continuum with the Balmer-line fluxes.

The recent measurements of internal variations of helium in Galactic and extragalactic Globular Clusters (GCs) set binding constraints to the models of formation of Multiple Populations (MPs) in GCs, and gave rise, at the same time, to crucial questions related with the influence of the environment on MP formation as well as with the role played by GCs in the early galactic formation. We present the most recent estimates of helium enrichment in the main populations of a large sample of Galactic and extragalactic GCs.

We studied a sample of 1672 galaxies in regions where a GRB event had occurred, in order to determine if the galactic environment plays a significant role on these energetic events. The Luminosity Function distribution for these galaxies shows some interesting features. For instance, there is a decline on the Luminosity Function at Mr~ −20.5; a lack of flatness at Mr~ −14 and higher-than-expected values of Φ(Mr) for Mr < −22.5. A comparison between our data and the Void, Wall and Early galaxies Luminosity Function was performed.

We derive the optical afterglow luminosity distributions at different epoches for gamma-ray bursts (GRBs) from a sample of 146 GRBs that have a well-sampled optical afterglow lightcurve, then explore the luminosity function of GRB optical afterglows using the Monte Carlo simulation. We show that an intrinsic broken power-law luminosity function can well reproduced the observed magnitude distributions.

We present a study of the evolution of early-type galaxies (ETGs) that combines luminosity function and clustering measurements. This technique shows that ETGs at a given redshift evolve into brighter galaxies in the rest-frame passively evolved optical at lower redshifts. Notice that this indicates that a stellar-mass selection at different redshifts does not necessarily provide samples of galaxies in a progenitor-descendant relationship. The comparison between high redshift ETGs and their likely descendants at z = 0 points to a higher number density for the progenitors by a factor 3 to 11, implying the need for mergers to decrease their number density by today. Because the progenitor-to-descendant ratios of luminosity density are consistent with the unit value, our results show no need for strong star-formation episodes in ETGs since z = 1, which indicates that the needed mergers are dry, i.e. gas free.

Historically, low luminosity stars have attracted very little attention, in part because they are difficult to see except with large telescopes, however, by neglecting to study them we are leaving out the vast majority of stars in the Universe. Low mass stars evolve very slowly, it takes them trillions of years to burn their hydrogen, after which, they just turn into a He white dwarf, without ever going through the red giant phase. This lack of observable evolution partly explains the lack of interest in them. The search for the “missing mass” in the galactic plane turned things around and during the 60s and 70s the search for large M/L objects placed M-dwarfs and cool WDs among objects of astrophysical interest. New fields of astronomical research, like BDs and exoplanets appeared as spin-offs from efforts to find the “missing mass”. The search for halo white dwarfs, believed to be responsible for the observed microlensing events, is pursued by several groups. The progress in these last few years has been tremendous, here I present highlights some of the great successes in the field and point to some of the still unsolved issues.

This work deals with a CCD imaging study at optical and near-infrared wavelength of two giant molecular clouds (plus a control field) in the southern region of the Large Magellanic Cloud, one of which shows multiple signs of star formation, whereas the other does not. The observational data from VLT FORS2 (R-band) and NTT SOFI (Ks-band) have been analyzed to derive luminosity functions and color-magnitude diagrams. The young stellar content of these two giant molecular clouds is compared and confirmed to be different, in the sense that the apparently “starless” cloud has so far formed only low-luminosity, low-mass stars (fainter than mKs = 16.5 mag, not seen by 2MASS), while the other cloud has formed both faint low-mass and luminous high-mass stars. The surface density excess of low-luminosity stars (~ 2 per square arcmin) in the “starless” cloud with respect to the control field is about 20% whereas the excess is about a factor of 3 in the known star-forming cloud. The difference may be explained theoretically by the gravo-turbulent evolution of giant molecular clouds, one being younger and less centrally concentrated than the other.

We have derived a complete magnitude-limited sample of 440 Galactic open clusters in the solar neighborhood, with integrated V-magnitude brighter than 8 mag. This sample can be used to infer the present-day luminosity and mass functions of open clusters up to a given age; it can even be used to construct the initial mass and luminosity function (IMF, ILF) of clusters (defined as visible clusters with age 4 – 8 Myr). The high-mass end of the cluster IMF is a power-law with a slope of −2 or slightly shallower (−1.7) while the luminous cluster ILF has a power-slope of −1, in agreement with what is found for extragalactic clusters. Both distribution functions show a turnover, starting at 300 M⊙ and integrated magnitude −3 mag, respectively. The overall birthrate of clusters is 0.4 clusters per kpc2 and per Myr. The average present-day cluster mass is 700 M⊙, while the average initial cluster mass is 4500 M⊙. The difference of these two average masses indicates the high infant mortality and/or weight loss of Galactic open clusters (due to dynamical evolution).

The analysis of the R-band luminosity function of galaxies in substructures of 21 Abell clusters shows that the characteristic magnitude M* for dominant substructure is brighter than in the second substructure and the magnitude gap between two brightest galaxies in dominant substructure is larger than in the second one.

The stellar Initial Mass Function (IMF) is a quantity which accounts for the distribution of the masses of stars, when they are formed. All the information available on the IMF in the low-mass regime comes from studies of our galaxy alone. Investigations on the content of low-mass stars in other neighbouring galaxies are limited by observational constraints, which do not allow the detection of the fainter stars with statistical significance. Only recently results from observations with the Hubble Space Telescope (HST) of stellar populations in the Large Magellanic Cloud (LMC) down to $\sim$ 0.7 M$_\odot$ confirm systematic variations in the low-mass IMF expected from theoretical considerations (Gouliermis et al. 2005). Direct imaging of resolved stellar populations in massive young clusters throughout the Local Group would be possible with Extremely Large Telescopes (ELTs). Hence, a sizeable sample of young clusters for which IMF variations can be detected would become available. We present our method for testing the efficiency of observations with ELTs in detecting low-mass stars in compact clusters of the Local Group galaxies. We plan to simulate imaging with ELTs and use the results of their photometry in order to investigate the effect on the derived low-mass IMF. This method demonstrates the advantages that will be introduced to crowded field photometry in close-by galaxies with ELTs.

In this contribution, we report on the discovery of dwarf spheroidals (dSphs) in the core of the Fornax cluster. Their photometric properties – like magnitude, colour, surface brightness – are very similar to those of Local Group dSphs. However, at a given total magnitude, dSphs in Fornax seem to be more extended than their Local Group counterparts. The membership of several dwarf galaxy candidates in Fornax has been confirmed by surface brightness fluctuation measurements on deep wide-field images taken with the Magellan telescope. The analysis of these images also confirms the flat faint end slope of the luminosity function for dSphs in Fornax which contradicts the expected large number of small dark matter halos connected to dwarf galaxies in $\Lambda$CDM theory. Dwarf spheroidals have also been detected in the Hydra I and Centaurus cluster. A preliminary analysis of their photometric properties shows that they obey similar scaling relations as their counterparts in Fornax and the Local Group.