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Evolution of dust temperature of galaxies through cosmic time as seen by <i>Herschel</i><sup>★</sup>
Hwang, H. S.,Elbaz, D.,Magdis, G.,Daddi, E.,Symeonidis, M.,Altieri, B.,Amblard, A.,Andreani, P.,Arumugam, V.,Auld, R.,Aussel, H.,Babbedge, T.,Berta, S.,Blain, A.,Bock, J.,Bongiovanni, A.,Boselli, A.,B Blackwell Publishing Ltd 2010 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.409 No.1
<P>ABSTRACT</P><P>We study the dust properties of galaxies in the redshift range 0.1 ≲<I>z</I>≲ 2.8 observed by the <I>Herschel Space Observatory</I> in the field of the Great Observatories Origins Deep Survey-North as part of the PACS Extragalactic Probe (PEP) and <I>Herschel</I> Multi-tiered Extragalactic Survey (HerMES) key programmes. Infrared (IR) luminosity (<I>L</I><SUB>IR</SUB>) and dust temperature (<I>T</I><SUB>dust</SUB>) of galaxies are derived from the spectral energy distribution fit of the far-IR (FIR) flux densities obtained with the PACS and SPIRE instruments onboard <I>Herschel</I>. As a reference sample, we also obtain IR luminosities and dust temperatures of local galaxies at <I>z</I> < 0.1 using <I>AKARI</I> and <I>IRAS</I> data in the field of the Sloan Digital Sky Survey. We compare the <I>L</I><SUB>IR</SUB>–<I>T</I><SUB>dust</SUB> relation between the two samples and find that the median <I>T</I><SUB>dust</SUB> of <I>Herschel</I>-selected galaxies at <I>z</I>≳ 0.5 with <I>L</I><SUB>IR</SUB>≳ 5 × 10<SUP>10</SUP> L<SUB>⊙</SUB> appears to be 2–5 K colder than that of <I>AKARI</I>-selected local galaxies with similar luminosities, and the dispersion in <I>T</I><SUB>dust</SUB> for high-<I>z</I> galaxies increases with <I>L</I><SUB>IR</SUB> due to the existence of cold galaxies that are not seen among local galaxies. We show that this large dispersion of the <I>L</I><SUB>IR</SUB>−<I>T</I><SUB>dust</SUB> relation can bridge the gap between local star-forming galaxies and high-<I>z</I> submillimetre galaxies (SMGs). We also find that three SMGs with very low <I>T</I><SUB>dust</SUB> (≲20 K) covered in this study have close neighbouring sources with similar 24-μm brightness, which could lead to an overestimation of FIR/(sub)millimetre fluxes of the SMGs.</P>
The multiple merger assembly of a hyperluminous obscured quasar at redshift 4.6
Dí,az-Santos, T.,Assef, R. J.,Blain, A. W.,Aravena, M.,Stern, D.,Tsai, C.-W.,Eisenhardt, P.,Wu, J.,Jun, H. D.,Dibert, K.,Inami, H.,Lansbury, G.,Leclercq, F. American Association for the Advancement of Scienc 2018 Science Vol.362 No.6418
<P><B>Mergers drive a powerful dusty quasar</B></P><P>Massive galaxies in the early Universe host supermassive black holes at their centers. When material falls toward the black hole, it releases energy and is observed as a quasar. Astronomers found a population of powerful distant quasars that are obscured by dust, but it has been unclear how they are formed. Díaz-Santos <I>et al.</I> observed the dust-obscured quasar WISE J224607.56-052634.9 at submillimeter wavelengths, finding three small companion galaxies connected to the quasar by bridges of gas and dust. They inferred that galaxy mergers can provide both the raw material to power a quasar and large quantities of dust to obscure it.</P><P><I>Science</I>, this issue p. 1034</P><P>Galaxy mergers and gas accretion from the cosmic web drove the growth of galaxies and their central black holes at early epochs. We report spectroscopic imaging of a multiple merger event in the most luminous known galaxy, WISE J224607.56−052634.9 (W2246−0526), a dust-obscured quasar at redshift 4.6, 1.3 billion years after the Big Bang. Far-infrared dust continuum observations show three galaxy companions around W2246−0526 with disturbed morphologies, connected by streams of dust likely produced by the dynamical interaction. The detection of tidal dusty bridges shows that W2246−0526 is accreting its neighbors, suggesting that merger activity may be a dominant mechanism through which the most luminous galaxies simultaneously obscure and feed their central supermassive black holes.</P>