We describe the search for Lyman-break galaxies (LBGs) near the sub-millimeter bright starburst galaxy HFLS3 at $z$$=$6.34 and a study on the environment of this massive galaxy during the end of reionization.We performed two independent selections of
LBGs on images obtained with the textit{Gran Telescopio Canarias} (GTC) and the textit{Hubble Space Telescope} (HST) by combining non-detections in bands blueward of the Lyman-break and color selection. A total of 10 objects fulfilling the LBG selection criteria at $z$$>$5.5 were selected over the 4.54 and 55.5 arcmin$^2$ covered by our HST and GTC images, respectively. The photometric redshift, UV luminosity, and the star-formation rate of these sources were estimated with models of their spectral energy distribution. These $z$$sim$6 candidates have physical properties and number densities in agreement with previous results. The UV luminosity function at $z$$sim$6 and a Voronoi tessellation analysis of this field shows no strong evidence for an overdensity of relatively bright objects (m$_{F105W}$$<$25.9) associated with textit{HFLS3}. However, the over-density parameter deduced from this field and the surface density of objects can not excluded definitively the LBG over-density hypothesis. Moreover we identified three faint objects at less than three arcseconds from textit{HFLS3} with color consistent with those expected for $z$$sim$6 galaxies. Deeper data are needed to confirm their redshifts and to study their association with textit{HFLS3} and the galaxy merger that may be responsible for the massive starburst.
We study the crystalline and electronic properties of the $textrm{Fe}_{1-x}textrm{Co}_xtextrm{Se}$ system ($x=0$, 0.25, 0.5, 0.75, and 1.0) using X-ray diffraction, X-ray spectroscopy and density functional theory. We show that the introduction of Co
$3d$ states in FeSe relaxes the bond strengths and induces a structural transition from tetragonal to hexagonal whose crossover takes place at $xapprox0.38$. This structural transition in turn modifies the magnetic order which can be related to the spin state. Using resonant inelastic X-ray spectroscopy we estimate the spin state of the system; FeSe is found to be in a high spin state (S=2), but Fe is reduced to a low spin state upon Co substitution of $x le 0.25$, well below the structural transition. Finally, we show evidence that FeSe is a moderately correlated system but the introduction of Co into the host lattice weakens the correlation strength for $xge0.25$. These novel findings are important to unravel the mechanisms responsible for the superconducting state in iron-chalcogenide superconductors.
We study the electronic properties of the $textrm{Fe}textrm{Se}_{1-x}textrm{Te}_x$ system ($x=0$, 0.25, 0.5, 0.75, and 1) from the perspective of X-ray spectroscopy and density functional theory (DFT). The analysis performed on the density of states
reveals marked differences in the distribution of the $5p$ states of Te for $x>0$. We think that this finding can be associated with the fact that superconductivity is suppressed in FeTe. Moreover, using resonant inelastic X-ray scattering, we estimate the spin state of our system which can be correlated to the magnetic order. We find that the spin state of the $textrm{Fe}textrm{Se}_{1-x}textrm{Te}_x$ system fluctuates, as a function of $x$, between $S=0$ and $S=2$ with Fe in FeSe in the highest spin state. Finally, our DFT calculations nicely reproduce the X-ray emission spectra performed at the Fe $L$-edge (which probe the occupied states) and suggest that the $textrm{Fe}textrm{Se}_{1-x}textrm{Te}_x$ system can be considered at most as a moderately correlated system.
Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectrosc
opy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S_500>100 mJy, 21 are strongly lensed (multiply imaged), 4 are moderately lensed (singly imaged), and the remainder require additional data to determine their lensing status. We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (r_half) and far-infrared luminosities (L_FIR) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at z_lens>0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500um flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in L_FIR (median L_FIR=7.9x10^12 L_sun) and two decades in FIR luminosity surface density (median Sigma_FIR=6.0x10^11 L_sun kpc^-2). The strong lenses in this sample and others identified via (sub-)mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift.
Within the framework of the Herschel M 33 extended survey HerM33es we study the Spectral Energy Distribution (SED) of a set of HII regions in M 33 as a function of the morphology. We present a catalogue of 119 HII regions morphologically classified:
9 filled, 47 mixed, 36 shell, and 27 clear shell HII regions. For each object we extract the photometry at twelve available wavelength bands (from FUV-1516A to IR-250mi) and obtain the SED. We also obtain emission line profiles across the regions to study the location of the stellar, ionised gas, and dust components. We find trends for the SEDs related to the morphology, showing that the star and gas-dust configuration affects the ratios of the emission in different bands. The mixed and filled regions show higher emission at 24mi than the shells and clear shells, which could be due to the proximity of the dust to the stellar clusters in the case of mixed and filled regions. The FIR peak for shells and clear shells seems to be located towards longer wavelengths, indicating that the dust is colder for this type of objects.The logarithmic 100/70mi ratio for filled and mixed regions remains constant over one order of magnitude in Halpha and FUV surface brightness, while the shells and clear shells exhibit a wider range of values of almost two orders of magnitude. We derive dust masses and temperatures fitting the individual SEDs with dust models proposed in the literature. The derived dust mass range is between 10^2-10^4 Msun and the cold dust temperature spans T(cold)~12-27 K. The spherical geometrical model proposed for the Halpha clear shells is confirmed by the emission profile obtained from the observations and is used to infer the electron density within the envelope: the typical electron density is 0.7+-0.3 cm^-3, while filled regions can reach values two to five times higher.
Within the framework of the HerM33es Key Project for Herschel and in combination with multi-wavelength data, we study the Spectral Energy Distribution (SED) of a set of HII regions in the Local Group Galaxy M33. Using the Halpha emission, we perform
a classification of a selected HII region sample in terms of morphology, separating the objects in filled, mixed, shell and clear shell objects. We obtain the SED for each HII region as well as a representative SED for each class of objects. We also study the emission distribution of each band within the regions. We find different trends in the SEDs for each morphological type that are related to properties of the dust and their associated stellar cluster. The emission distribution of each band within the region is different for each morphological type of object.
We have analysed the rest-frame far infrared (FIR) properties of a sample of massive (Mstar > 10^11Msun) galaxies at 2<z<3 in the GOODS (Great Observatories Origins Deep Survey) North field using the Spectral and Photometric Imaging Receiver (SPIRE)
instrument aboard the Herschel Space Observatory. To conduct this analysis we take advantage of the data from the HerMES key program. The sample comprises 45 massive galaxies with structural parameters characterised with HST NICMOS-3. We study detections at submm Herschel bands, together with Spitzer 24{mu}m data, as a function of the morphological type, mass and size. We find that 26/45 sources are detected at MIPS-24{mu}m and 15/45 (all MIPS-24{mu}m detections) are detected at SPIRE-250{mu}m, with disk-like galaxies more easily detected. We derive star formation rates (SFR) and specific star formation rates (sSFR) by fitting the spectral energy distribution (SED) of our sources, taking into account non-detections for SPIRE and systematic effects for MIPS derived quantities. We find that the mean SFR for the spheroidal galaxies (50-100 Msun*yr^-1) is substantially (a factor ~ 3) lower than the mean value presented by disk-like galaxies (250-300 Msun*yr^-1).
In this paper we analyse the methodology to derive the bar pattern speed from dynamical simulations. The results are robust to the changes in the vertical-scale height and in the mass-to-light (M/L) ratios. There is a small range of parameters for wh
ich the kinematics can be fitted. We have also taken into account the use of different type of dynamical modelling and the effect of using 2-D vs 1-D models in deriving the pattern speeds. We conclude that the derivation of the bar streaming motions and strength and position of shocks is not greatly affected by the fluid dynamical model used. We show new results on the derivation of the pattern speed for NGC 1530. The best fit pattern speed is around 10 km/s/kpc, which corresponds to a R_cor/R_bar = 1.4, implying a slower bar than previously derived from more indirect assumptions. With this pattern speed, the global and most local kinematic features are beautifully reproduced. However, the simulations fail to reproduce the velocity gradients close to some bright HII regions in the bar. We have shown from the study of the Halpha equivalent widths that the HII regions that are located further away from the bar dust-lane in its leading side, downstream from the main bar dust-lane, are older than the rest by 1.5-2.5 Myr. In addition, a clear spatial correlation was found between the location of HII regions, dust spurs on the trailing side of the bar dust-lane, and the loci of maximum velocity gradients parallel to the bar major axis.
We present results on low-resolution mid-infrared (MIR) spectra of 70 infrared-luminous galaxies obtained with the Infrared Spectrograph (IRS) onboard Spitzer. We selected sources from the European Large Area Infrared Survey (ELAIS) with S15 > 0.8 mJ
y and photometric or spectroscopic z > 1. About half of the sample are QSOs in the optical, while the remaining sources are galaxies, comprising both obscured AGN and starbursts. We classify the spectra using well-known infrared diagnostics, as well as a new one that we propose, into three types of source: those dominated by an unobscured AGN (QSOs), obscured AGN, and starburst-dominated sources. Starbursts concentrate at z ~ 0.6-1.0 favored by the shift of the 7.7-micron PAH band into the selection 15 micron band, while AGN spread over the 0.5 < z < 3.1 range. Star formation rates (SFR) are estimated for individual sources from the luminosity of the PAH features. An estimate of the average PAH luminosity in QSOs and obscured AGN is obtained from the composite spectrum of all sources with reliable redshifts. The estimated mean SFR in the QSOs is 50-100 Mo yr^-1, but the implied FIR luminosity is 3-10 times lower than that obtained from stacking analysis of the FIR photometry, suggesting destruction of the PAH carriers by energetic photons from the AGN. The SFR estimated in obscured AGN is 2-3 times higher than in QSOs of similar MIR luminosity. This discrepancy might not be due to luminosity effects or selection bias alone, but could instead indicate a connection between obscuration and star formation. However, the observed correlation between silicate absorption and the slope of the near- to mid-infrared spectrum is compatible with the obscuration of the AGN emission in these sources being produced in a dust torus.
