University of Crete

About: University of Crete is a education organization based out in Rethymno, Greece. It is known for research contribution in the topics: Population & Galaxy. The organization has 8681 authors who have published 21684 publications receiving 709078 citations. The organization is also known as: Panepistimio Kritis.

The great observatories all-sky lirg survey: comparison of ultraviolet and far-infrared properties

Abstract: The Great Observatories All-sky LIRG Survey (GOALS) consists of a complete sample of 202 luminous infrared galaxies (LIRGs) selected from the IRAS Revised Bright Galaxy Sample (RBGS). The galaxies span the full range of interaction stages, from isolated galaxies to interacting pairs to late stage mergers. We present a comparison of the UV and infrared properties of 135 galaxies in GOALS observed by GALEX and Spitzer. For interacting galaxies with separations greater than the resolution of GALEX and Spitzer (~2"-6"), we assess the UV and IR properties of each galaxy individually. The contribution of the FUV to the measured star formation rate (SFR) ranges from 0.2% to 17.9%, with a median of 2.8% and a mean of 4.0% ± 0.4%. The specific star formation rate (SSFR) of the GOALS sample is extremely high, with a median value (3.9 × 10^(–10) yr^(–1)) that is comparable to the highest SSFRs seen in the Spitzer Infrared Nearby Galaxies Survey sample. We examine the position of each galaxy on the IR excess-UV slope (IRX-β) diagram as a function of galaxy properties, including IR luminosity and interaction stage. The LIRGs on average have greater IR excesses than would be expected based on their UV colors if they obeyed the same relations as starbursts with L_(IR) 0). Among resolved interacting systems, 32% contain one galaxy which dominates the IR emission while the companion dominates the UV emission. Only 21% of the resolved systems contain a single galaxy which dominates both wavelengths.

Constraining the properties of AGN host galaxies with spectral energy distribution modelling

Abstract: Detailed studies of the spectral energy distribution (SED) of normal galaxies have increasingly been used to understand the physical mechanism dominating their integrated emission, mainly owing to the availability of high quality multi-wavelength data from the UV to the far-infrared (FIR). However, systems hosting dust-enshrouded nuclear starbursts and/or an accreting supermassive black hole (an active galactic nucleus or AGN) are especially challenging to study. This is due to the complex interplay between the heating by massive stars and the AGN, the absorption and emission of radiation from dust, as well as the presence of the underlying old stellar population. We used the latest release of CIGALE, a fast state-of-the-art galaxy SED-fitting model relying on energy balance, to study the influence of an AGN in a self consistent manner in estimating both the star formation rate (SFR) and stellar mass in galaxies, as well as to calculate the contribution of the AGN to the power output of the host. Using the semi-analytical galaxy formation model galform, we created a suite of mock galaxy SEDs using realistic star formation histories (SFH). We also added an AGN of Type-1, Type-2, or intermediate-type whose contribution to the bolometric luminosity can be variable. We performed an SED-fitting of these catalogues with CIGALE, assuming three different SFHs: a single-exponentially-decreasing (1τ-dec), a double-exponentially-decreasing (2τ-dec), and a delayed SFH. Constraining the overall contribution of an AGN to the total infrared luminosity (fracAGN) is very challenging for fracAGN< 20%, with uncertainties of ~5–30% for higher fractions depending on the AGN type, while FIR and sub-mm are essential. The AGN power has an impact on the estimation of M∗ in Type-1 and intermediate-type AGNs but has no effect on galaxies hosting Type-2 AGNs. We find that in the absence of AGN emission, the best estimates of M∗ are obtained using the 2τ-dec model but at the expense of realistic ages of the stellar population. The delayed SFH model provides good estimates of M∗ and SFR, with a maximum offset of 10% as well as better estimates of the age. Our analysis shows that the under-estimation of the SFR increases with fracAGN for Type-1 systems, as well as for low contributions of an intermediate AGN type, but it is quite insensitive to the emission of Type-2 AGNs up to fracAGN ~ 45%. A lack of sampling the FIR, or sub-mm domain systematically over-estimates the SFR (<20%), independent of the contribution of the AGN. Similarly, the UV emission is critical in accurately retrieving both the M∗ for Type-1 and intermediate- type AGN and the SFR of all three AGN types. We show that the presence of AGN emission introduces a scatter to the SFR-M∗ main sequence relation derived from SED-fitting, which is driven by the uncertainties on M∗. Finally, we used our mock catalogues to test the popular IR SED-fitting code DecompIR and show that fracAGN is under-estimated but that the SFR is recovered well for Type-1 and intermediate-types of AGN. The fracAGN, SFR, and LIR estimates of Type-2 AGNs are more problematic owing to a FIR emission disagreement between predicted and observed models.

Open-cage fullerenes: towards the construction of nanosized molecular containers

Abstract: Open-cage fullerene derivatives have excited organic chemists’ creativity over the past decade. These adducts, generated via consecutive cleavage of σ- and π-carbon–carbon bonds on the fullerene cage, allow small atoms or molecules to pass through their opening and be placed inside the cavity. Restoration of the ruptured fullerene back to the pristine fullerene cage affords the corresponding endohedral complexes. This “molecular surgery” approach has been proposed as an alternative to the synthesis of endohedral fullerenes via the conventional physical methods of production, which restrict the availability of endohedral fullerenes to milligram quantities after laborious isolation procedures. In this critical review, we survey all published techniques for the creation of an orifice, as well as for the expansion of an existing one, on the fullerene framework. Successful encapsulation experiments employing cage-opened fullerene derivatives are also comprehensively discussed (160 references).

GOODS-Herschel and CANDELS: The Morphologies of Ultraluminous Infrared Galaxies at z ~ 2

Abstract: Using deep 100 and 160 μm observations in GOODS-South from GOODS-Herschel, combined with high-resolution HST/WFC3 near-infrared imaging from CANDELS, we present the first detailed morphological analysis of a complete, far-infrared (FIR) selected sample of 52 ultraluminous infrared galaxies (ULIRGs; L IR > 1012 L ☉) at z ~ 2. We also make use of a comparison sample of galaxies with lower IR luminosities but with the same redshift and H-band magnitude distribution. Our visual classifications of these two samples indicate that the fractions of objects with disk and spheroid morphologies are roughly the same but that there are significantly more mergers, interactions, and irregular galaxies among the ULIRGs (72+5 – 7% versus 32 ± 3%). The combination of disk and irregular/interacting morphologies suggests that early-stage interactions, minor mergers, and disk instabilities could play an important role in ULIRGs at z ~ 2. We compare these fractions with those of a z ~ 1 sample selected from GOODS-H and COSMOS across a wide luminosity range and find that the fraction of disks decreases systematically with L IR while the fraction of mergers and interactions increases, as has been observed locally. At comparable luminosities, the fraction of ULIRGs with various morphological classifications is similar at z ~ 2 and z ~ 1, though there are slightly fewer mergers and slightly more disks at higher redshift. We investigate the position of the z ~ 2 ULIRGs, along with 70 z ~ 2 LIRGs, on the specific star formation rate versus redshift plane, and find 52 systems to be starbursts (i.e., they lie more than a factor of three above the main-sequence relation). We find that many of these systems are clear interactions and mergers (~50%) compared to only 24% of systems on the main sequence relation. If irregular disks are included as potential minor mergers, then we find that up to ~73% of starbursts are involved in a merger or interaction at some level. Although the final coalescence of a major merger may not be required for the high luminosities of ULIRGs at z ~ 2 as is the case locally, the large fraction (50%-73%) of interactions at all stages and potential minor mergers suggests that these processes contribute significantly to the high star formation rates of ULIRGs at z ~ 2.

Past, present and future atmospheric nitrogen deposition

Abstract: Reactive nitrogen emissions into the atmosphere are increasing due to human activities, affecting nitrogen deposition to the surface and impacting the productivity of terrestrial and marine ecosystems. An atmospheric chemistry-transport model (TM4-ECPL) is here used to calculate the global distribution of total nitrogen deposition, accounting for the first time for both its inorganic and organic fractions in gaseous and particulate phases, and past and projected changes due to anthropogenic activities. The anthropogenic and biomass burning ACCMIP historical and RCP6.0 and RCP8.5 emissions scenarios are used. Accounting for organic nitrogen (ON) primary emissions, the present-day global nitrogen atmospheric source is about 60% anthropogenic, while total N deposition increases by about 20% relative to simulations without ON primary emissions. About 20-25% of total deposited N is ON. About 10% of the emitted nitrogen oxides are deposited as ON instead of inorganic nitrogen (IN) as is considered in most global models. Almost a 3-fold increase over land (2-fold over the ocean) has been calculated for soluble N deposition due to human activities from 1850 to present. The investigated projections indicate significant changes in the regional distribution of N deposition and chemical composition, with reduced compounds gaining importance relative to oxidized ones, but very small changes in the global total flux. Sensitivity simulations quantify uncertainties due to the investigated model parameterizations of IN partitioning onto aerosols and of N chemically fixed on organics to be within 10% for the total soluble N deposition and between 25-35% for the dissolved ON deposition. Larger uncertainties are associated with N emissions.