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Register a new userThe HerMES sub-millimetre local and low-redshift luminosity functions
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We used wide area surveys over 39 deg$^2$ by the HerMES collaboration, performed with the Herschel Observatory SPIRE multi-wavelength camera, to estimate the low-redshift, $0.02<z<0.5$, monochromatic luminosity functions (LFs) of galaxies at 250, 350 and 500$,mu$m. SPIRE flux densities were also combined with Spitzer photometry and multi-wavelength archival data to perform a complete SED fitting analysis of SPIRE detected sources to calculate precise k-corrections, as well as the bolometric infrared (8-1000$,mu$m) luminosity functions and their low-$z$ evolution from a combination of statistical estimators. Integration of the latter prompted us to also compute the local luminosity density (LLD) and the comoving star formation rate density (SFRD) for our sources, and to compare them with theoretical predictions of galaxy formation models. The luminosity functions show significant and rapid luminosity evolution already at low redshifts, $0.02<z<0.2$, with L$_{IR}^* propto (1+z)^{6.0pm0.4}$ and $Phi_{IR}^* propto (1+z)^{-2.1pm0.4}$, L$_{250}^* propto (1+z)^{5.3pm0.2}$ and $Phi_{250}^* propto (1+z)^{-0.6pm0.4}$ estimated using the IR bolometric and the 250$,mu$m LFs respectively. Converting our IR LD estimate into an SFRD assuming a standard Salpeter IMF and including the unobscured contribution based on the UV dust-uncorrected emission from local galaxies, we estimate a SFRD scaling of SFRD$_0+0.08 z$, where SFRD$_0simeq (1.9pm 0.03)times 10^{-2} [mathrm{M}_odot,mathrm{Mpc}^{-3}]$ is our total SFRD estimate at $zsim0.02$.
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We examine the rest-frame far-infrared emission from powerful radio sources with 1.4GHz luminosity densities of 25<=log(L_1.4/WHz^-1)<=26.5 in the extragalactic Spitzer First Look Survey field. We combine Herschel/SPIRE flux densities with Spitzer/IRAC and MIPS infrared data to obtain total (8-1000um) infrared luminosities for these radio sources. We separate our sources into a moderate, 0.4<z<0.9, and a high, 1.2<z<3.0, redshift sub-sample and we use Spitzer observations of a z<0.1 3CRR sample as a local comparison. By comparison to numbers from the SKA Simulated Skies we find that our moderate redshift sample is complete and our high redshift sample is 14per cent complete. We constrain the ranges of mean star formation rates (SFRs) to be 3.4-4.2, 18-41 and 80-581Msun/yr for the local, moderate and high redshift samples respectively. Hence, we observe an increase in the mean SFR with increasing redshift which we can parameterise as ~(1+z)^Q, where Q=4.2+/-0.8. However we observe no trends of mean SFR with radio luminosity within the moderate or high redshift bins. We estimate that radio-loud AGN in the high redshift sample contribute 0.1-0.5per cent to the total SFR density at that epoch. Hence, if all luminous starbursts host radio-loud AGN we infer a radio-loud phase duty cycle of 0.001-0.005.
Local luminosity functions are fundamental benchmarks for high-redshift galaxy formation and evolution studies as well as for models describing these processes. Determining the local luminosity function in the submillimeter range can help to better constrain in particular the bolometric luminosity density in the local Universe, and Herschel offers the first opportunity to do so in an unbiased way by imaging large sky areas at several submillimeter wavelengths. We present the first Herschel measurement of the submillimeter 0<z<0.2 local luminosity function and infrared bolometric (8-1000 $mu$m) local luminosity density based on SPIRE data from the HerMES Herschel Key Program over 14.7 deg^2. Flux measurements in the three SPIRE channels at 250, 350 and 500 mum are combined with Spitzer photometry and archival data. We fit the observed optical-to-submillimeter spectral energy distribution of SPIRE sources and use the 1/V_{max} estimator to provide the first constraints on the monochromatic 250, 350 and 500 mum as well as on the infrared bolometric (8-1000 mum) local luminosity function based on Herschel data. We compare our results with modeling predictions and find a slightly more abundant local submillimeter population than predicted by a number of models. Our measurement of the infrared bolometric (8-1000 mum) local luminosity function suggests a flat slope at low luminosity, and the inferred local luminosity density, 1.31_-0.21^+0.24 x 10^8 Lsun Mpc^-3, is consistent with the range of values reported in recent literature.
The satellite populations of the Milky Way, and Milky-Way-mass galaxies in the local universe, have been extensively studied to constrain dark-matter and galaxy-evolution physics. Recently, there has been a shift to studying satellites of hosts with stellar masses between that of the Large Magellanic Cloud and the Milky Way, since they can provide further insight on hierarchical structure formation, environmental effects on satellites, and the nature of dark-matter. Most work is focused on the Local Volume, and little is still known about low-mass host galaxies at higher red-shift. To improve our understanding of the evolution of satellite populations of low-mass hosts, we study satellite galaxy populations as a function of host stellar mass $9.5 < log(M_*/M_odot) < 10.5$ and redshifts $0.1 < z < 0.8$ in the COSMOS survey, making this the first study of satellite systems of low-mass hosts across half the age of the universe. We find that the satellite populations of low-mass host galaxies, which we measure down to satellite masses equivalent to the Fornax dwarf spheroidal satellite of the Milky Way, remain mostly unchanged through time. We observe a weak dependence between host stellar mass and number of satellites per host, which suggests that the stellar masses of the hosts are in the power-law regime of the stellar mass to halo mass relation $(M_*-M_{text{halo}})$ for low-mass galaxies. Finally, we test the constraining power of our measured cumulative luminosity function to calculate the low-mass end slope of the $M_*-M_text{halo}$ relation. These new satellite luminosity function measurements are consistent with ${Lambda}$CDM predictions.
Late stages of stellar evolution are characterized by copious mass-loss events whose signature is the formation of circumstellar envelopes (CSE). Planck multi-frequency measurements have provided relevant information on a sample of Galactic planetary nebulae (PNe) in the important and relatively unexplored observational band between 30 and 857GHz. Planck enables the assembly of comprehensive PNe spectral energy distributions (SEDs) from radio {bf to} far-infrared frequencies. Modelling of the derived SEDs provides us with information on physical properties of CSEs and the mass content of both main components: ionised gas, traced by the free-free emission at cm--mm waves; and thermal dust, traced by the millimetre and far-IR emission. In particular, the amount of ionised gas and dust has been derived here. Such quantities have also been estimated for the very young PN CRL618, where the strong variability observed in its radio and millimetre emission has previously prevented the construction of its SED. A morphological study of the Helix Nebula has also been performed. Planck maps reveal, for the first time, the spatial distribution of the dust inside the envelope, allowing us to identify different components, the most interesting of which is a very extended component (up to 1pc) that may be related to a region where the slow expanding envelope is interacting with the surrounding interstellar medium.
We characterize the local (2-kpc sized) environments of Type Ia, II, and Ib/c supernovae (SNe) that have recently occurred in nearby ($dlesssim50$ Mpc) galaxies. Using ultraviolet (UV, from GALEX) and infrared (IR, from WISE) maps of 359 galaxies and a sample of 472 SNe, we measure the star formation rate surface density ($Sigma_{rm SFR}$) and stellar mass surface density ($Sigma_star$) in a 2-kpc beam centered on each SN site. We show that core-collapse SNe are preferentially located along the resolved galactic star-forming main sequence, whereas Type Ia SNe are extended to lower values of $Sigma_{rm SFR}$ at fixed $Sigma_star$, indicative of locations inside quiescent galaxies or quiescent regions of galaxies. We also test how well the radial distribution of each SN type matches the radial distributions of UV and IR light in each host galaxy. We find that, to first order, the distributions of all types of SNe mirror that of both near-IR light (3.4 and 4.5 microns, tracing the stellar mass distribution) and mid-IR light (12 and 22 microns, tracing emission from hot, small grains), and also resemble our best-estimate $Sigma_{rm SFR}$. All types of SNe appear more radially concentrated than the UV emission of their host galaxies. In more detail, the distributions of Type II SNe show small statistical differences from that of near-IR light. We attribute this overall structural uniformity to the fact that within any individual galaxy, $Sigma_{rm SFR}$ and $Sigma_star$ track one another well, with variations in $Sigma_{rm SFR}/Sigma_star$ most visible when comparing between galaxies.
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