Morphological Classification of Local Luminous Infrared Galaxies

We present an analysis of the morphological classification of 89 luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey (GOALS) sample using non-parametric coefficients and compare their morphology as a function of wavelength. We rely on images obtained in the optical (B- and I-band) as well as in the infrared (H-band and 5.8$\mu$m). Our classification is based on the calculation of $Gini$ and the second order of light ($M_{20}$) non-parametric coefficients which we explore as a function of stellar mass ($M_\star$), infrared luminosity ($L_{IR}$) and star formation rate (SFR). We investigate the relation between $M_{20}$, the specific SFR (sSFR) and the dust temperature ($T_{dust}$) in our galaxy sample. We find that $M_{20}$ is a better morphological tracer than $Gini$, as it allows to distinguish systems formed by double systems from isolated and post-merger LIRGs. The multi-wavelength analysis allows us to identify a region in the $Gini$-$M_{20}$ parameter space where ongoing mergers reside, regardless of the band used to calculate the coefficients. In particular when measured in the H-band, this region can be used to identify ongoing mergers, with a minimal contamination from LIRGs in other stages. We also find that while the sSFR is positively correlated with $M_{20}$ when measured in the mid-infrared, i.e. star-bursting galaxies show more compact emission, it is anti-correlated with the B-band based $M_{20}$. We interpret this as the spatial decoupling between obscured and un-obscured star formation, whereby the ultraviolet/optical size of a LIRGs experience an intense dust enshrouded central starburst is larger than in the one in the mid-infrared since the contrast between the nuclear to the extended disk emission is smaller in the mid-infrared. This has important implications for high redshift surveys of dusty sources. [abridged]Comment: ( 18 pages, 12 figures, Accepted for publication in A&A

Star-galaxy separation by far-infrared color-color diagrams for the AKARI FIS All-Sky Survey (Bright Source Catalogue Version beta-1)

To separate stars and galaxies in the far infrared AKARI All-Sky Survey data, we have selected a sample with the complete color information available in the low extinction regions of the sky and constructed color-color plots for these data. We looked for the method to separate stars and galaxies using the color information. We performed an extensive search for the counterparts of these selected All-Sky Survey sources in the NED and SIMBAD databases. Among 5176 objects, we found 4272 galaxies, 382 other extragalactic objects, 349 Milky Way stars, 50 other Galactic objects, and 101 sources detected before in various wavelengths but of an unknown origin. 22 sources were left unidentified. Then, we checked colors of stars and galaxies in the far-infrared flux-color and color-color plots. In the resulting diagrams, stars form two clearly separated clouds. One of them is easy to be distinguished from galaxies and allows for a simple method of excluding a large part of stars using the far-infrared data. The other smaller branch, overplotting galaxies, consists of stars known to have an infrared excess, like Vega and some fainter stars discovered by IRAS or 2MASS. The color properties of these objects in any case make them very difficult to distinguish from galaxies. We conclude that the FIR color-color diagrams allow for a high-quality star-galaxy separation. With the proposed simple method we can select more that 95 % of galaxies rejecting at least 80 % of stars.Comment: 20 pages, 41 figures, "Astronomy & Astrophysics", accepted, to appear in the AKARI special issu

A bias in optical observations of high redshift luminous infrared galaxies

We present evidence for the dramatically different morphology between the rest frame UV and 7micron mid-IR emission of VV114 and Arp299, two nearby (z~0) violently interacting infrared luminous galaxies (LIRGs). Nearly all LIRGs are interacting systems and it is currently accepted that they dominate the IR emission at z>1. Luminous IR galaxies located at z=1-2 could easily be detected as unresolved sources in deep optical/near-IR ground based surveys, as well as in upcoming 24micron surveys with the Space Infrared Telescope Facility. We demonstrate that the spatial resolution of these surveys will result in blending of the emission from unresolved interacting components. An increased scatter will thus be introduced in the observed optical to mid-IR colors of these galaxies, leading to a systematic underestimation of their dust content.Comment: To appear in the Astrophysical Journal Letters (4 pages 1 figure

The radio properties of optically obscured Spitzer sources

This paper analyses the radio properties of a subsample of optically obscured (R>25.5) galaxies observed at 24um by the Spitzer Space Telescope within the First Look Survey. 96 F[24um]>0.35 mJy objects out of 510 are found to have a radio counterpart at 1.4 GHz, 610 MHz or at both frequencies respectively down to ~40uJy and ~200uJy. IRAC photometry sets the majority of them in the redshift interval z [1-3] and allows for a broad distinction between AGN-dominated galaxies (~47% of the radio-identified sample) and systems powered by intense star-formation (~13%), the remaining objects being impossible to classify. The percentage of radio identifications is a strong function of 24um flux. The radio number counts at both radio frequencies suggest that the physical process(es) responsible for radio activity in these objects have a common origin regardless of whether the source shows mid-IR emission compatible with being an obscured AGN or a star-forming galaxy. We also find that both candidate AGN and star-forming systems follow (although with a large scatter) the relationship between 1.4 GHz and 24um fluxes reported by Appleton et al. (2004) which identifies sources undergoing intense star formation activity. On the other hand, the inferred radio spectral indices alpha indicate that a large fraction of objects in our sample (~60% of all galaxies with estimated alpha) may belong to the population of Ultra Steep Spectrum (USS) Sources, typically 'frustrated' radio-loud AGN. We interpret our findings as a strong indication for concurrent AGN and star-forming activity, whereby the 1.4 GHz flux is of thermal origin, while that at 610 GHz mainly stems from the nuclear source.Comment: 18 pages, 16 figures, to appear in MNRA

Position statement and updated international guideline for safe and effective whole-body electromyostimulation training-the need for common sense in WB-EMS application

Whole-Body Electromyostimulation (WB-EMS) is a training technology that enables simultaneous stimulation of all the main muscle groups with a specific impulse intensity for each electrode. The corresponding time-efficiency and joint-friendliness of WB-EMS may be particularly attractive for people unable or unmotivated to conduct (intense) conventional training protocols. However, due to the enormous metabolic and musculoskeletal impact of WB-EMS, particular attention must be paid to the application of this technology. In the past, several scientific and newspaper articles reported severe adverse effects of WB-EMS. To increase the safety of commercial non-medical WB-EMS application, recommendations "for safe and effective whole-body electromyostimulation" were launched in 2016. However, new developments and trends require an update of these recommendations to incorporate more international expertise with demonstrated experience in the application of WB-EMS. The new version of these consensus-based recommendations has been structured into 1) "general aspects of WB-EMS", 2) "preparation for training", recommendations for the 3) "WB-EMS application" itself and 4) "safety aspects during and after training". Key topics particularly addressed are 1) consistent and close supervision of WB-EMS application, 2) mandatory qualification of WB-EMS trainers, 3) anamnesis and corresponding consideration of contraindications prior to WB-EMS, 4) the participant's proper preparation for the session, 5) careful preparation of the WB-EMS novice, 6) appropriate regeneration periods between WB-EMS sessions and 7) continuous interaction between trainer and participant at a close physical distance. In summary, we are convinced that the present guideline will contribute to greater safety and effectiveness in the area of non-medical commercial WB-EMS application

Clustering of star-forming galaxies detected in mid-infrared with the Spitzer wide-area survey

We discuss the clustering properties of galaxies with signs of ongoing star formation detected by the Spitzer Space Telescope at 24mum band in the SWIRE Lockman Hole field. The sample of mid-IR-selected galaxies includes ~20,000 objects detected above a flux threshold of S24mum=310muJy. We adopt optical/near-IR color selection criteria to split the sample into the lower-redshift and higher-redshift galaxy populations. We measure the angular correlation function on scales of theta=0.01-3.5 deg, from which, using the Limber inversion along with the redshift distribution established for similarly selected source populations in the GOODS fields (Rodighiero et al. 2010), we obtain comoving correlation lengths of r0=4.98+-0.28 h^-1 Mpc and r0 =8.04+-0.69 h^-1 Mpc for the low-z (=0.7) and high-z (=1.7) subsamples, respectively. Comparing these measurements with the correlation functions of dark matter halos identified in the Bolshoi cosmological simulation (Klypin et al. 2011}, we find that the high-redshift objects reside in progressively more massive halos reaching Mtot>3e12 h^-1 Msun, compared to Mtot>7e11 h^-1 Msun for the low-redshift population. Approximate estimates of the IR luminosities based on the catalogs of 24mum sources in the GOODS fields show that our high-z subsample represents a population of "distant ULIRGs" with LIR>10^12Lsun, while the low-z subsample mainly consists of "LIRGs", LIR~10^11Lsun. The comparison of number density of the 24mum selected galaxies and of dark matter halos with derived minimum mass Mtot shows that only 20% of such halos may host star-forming galaxies.Comment: 15 pages, 12 figure

New light on gamma-ray burst host galaxies with Herschel

Until recently, dust emission has been detected in very few host galaxies of gamma-ray bursts (GRBHs). With Herschel, we have now observed 17 GRBHs up to redshift z~3 and detected seven of them at infrared (IR) wavelengths. This relatively high detection rate (41%) may be due to the composition of our sample which at a median redshift of 1.1 is dominated by the hosts of dark GRBs. Although the numbers are small, statistics suggest that dark GRBs are more likely to be detected in the IR than their optically-bright counterparts. Combining our IR data with optical, near-infrared, and radio data from our own datasets and from the literature, we have constructed spectral energy distributions (SEDs) which span up to 6 orders of magnitude in wavelength. By fitting the SEDs, we have obtained stellar masses, dust masses, star-formation rate (SFR), and extinctions for our sample galaxies. We find that GRBHs are galaxies that tend to have a high specfic SFR (sSFR), and like other star-forming galaxies, their ratios of dust-to-stellar mass are well correlated with sSFR. We incorporate our Herschel sample into a larger compilation of GRBHs, and compare this combined sample to SFR-weighted median stellar masses of the widest, deepest galaxy survey to date. This is done in order to establish whether or not GRBs can be used as an unbiased tracer of cosmic comoving SFR density (SFRD) in the universe. In contrast with previous results, this comparison shows that GRBHs are medium-sized galaxies with relatively high sSFRs; stellar masses and sSFRs of GRBHs as a function of redshift are similar to what is expected for star-forming galaxy populations at similar redshifts. We conclude that there is no strong evidence that GRBs are biased tracers of SFRD; thus they should be able to reliably probe the SFRD to early epochs.Comment: 18 pages, 9 figures, accepted for publication in A&A. Revised to include Fig. 6, mistakenly omitted in origina