Herschel*-ATLAS: correlations between dust and gas in local submm-selected galaxies

We present an analysis of CO molecular gas tracers in a sample of 500 μ m-selected Herschel -ATLAS galaxies at z < 0 . 05 ( cz < 14990 km s − 1 ). Using 22 − 500 μ m photom- etry from WISE , IRAS and Herschel , with H i data from the literature, we investigate correlations between warm and cold dust, and tracers of the gas in different phases. The correlation between global CO(3–2) line fluxes and FIR–submm fl uxes weakens with increasing IR wavelength ( λ & 60 μ m), as a result of colder dust being less strongly associated with dense gas. Conversely, CO(2–1) and H i line fluxes both ap- pear to be better correlated with longer wavelengths, suggesting that cold dust is more strongly associated with diffuse atomic and molecular gas phases, co nsistent with it being at least partially heated by radiation from old stellar populations . The increased scatter at long wavelengths implies that sub-millimetre fluxes are a po orer tracer of SFR. Fluxes at 22 and 60 μ m are also better correlated with diffuse gas tracers than dense CO(3–2), probably due to very-small-grain emission in the diffu se interstellar medium, which is not correlated with SFR. The FIR/CO luminosity ratio a nd the dust mass/CO luminosity ratio both decrease with increasing luminosit y, as a result of either correlations between mass and metallicity (changing CO/H 2 ) or between CO luminosity and excitation [changing CO(3–2)/CO(1–0)].Web of Scienc

The torsion of a finite quasigroup quandle is annihilated by its order

We prove that if Q is a finite quasigroup quandle, then |Q| annihilates the torsion of its homology. It is a classical result in reduced homology of finite groups that the order of a group annihilates its homology. From the very beginning of the rack homology (between 1990 and 1995) the analogous result was suspected. The first general results in this direction were obtained independently about 2001 by R.A.Litherland and S.Nelson, and P.Etingof and M.Grana. In Litherland-Nelson paper it is proven that if (Q;*) is a finite homogeneous rack (this includes quasigroup racks) then the torsion of homology is annihilated by |Q|^n. In Etingof-Grana paper it is proven that if (X;A) is a finite rack and N=|G^0_Q| is the order of a group of inner automorphisms of Q, then only primes which can appear in the torsion of homology are those dividing N (the case of connected Alexander quandles was proven before by T.Mochizuki). The result of Litherland-Nelson is generalized by Niebrzydowski and Przytycki and in particular, they prove that the torsion part of the homology of the dihedral quandle R_3 is annihilated by 3. In Niebrzydowski-Przytycki paper it is conjectured that for a finite quasigroup quandle, torsion of its homology is annihilated by the order of the quandle. The conjecture is proved by T.Nosaka for finite Alexander quasigroup quandles. In this paper we prove the conjecture in full generality. For this version, we rewrote the Section 3 totally and introduced the concept of the precubic homotopy. In Section 2, the main addition is Corollary 2.2 which summarizes identities observed in the proof of the main theorem as we use it later in Section 3.Comment: 13 pages, 1 figure; accepted for publication in Journal of Pure and Applied Algebr

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

Herschel-ATLAS: the surprising diversity of dust-selected galaxies in the local submillimetre Universe

Galaxie

A dusty proto-cluster surrounding the binary galaxy HerBS-70 at z = 2.3

We report on deep SCUBA-2 observations at 850 μm and NOEMA spectroscopic measurements at 2 mm of the environment surrounding the luminous, massive (M* ≈ 2 × 1011 M⊙) Herschel-selected source HerBS-70. This source was revealed by previous NOEMA observations to be a binary system of dusty star-forming galaxies at z = 2.3, with the East component (HerBS-70E) hosting an Active Galactic Nucleus (AGN). The SCUBA-2 observations detected, in addition to the binary system, twenty-one sources at >3.5σ over an area of ∼25 square comoving Mpc with a sensitivity of 1σ850 = 0.75 mJy. The surface density of continuum sources around HerBS-70 is three times higher than for field galaxies. The NOEMA spectroscopic measurements confirm the protocluster membership of three of the nine brightest sources through their CO(4–3) line emission, yielding a volume density 36 times higher than for field galaxies. All five confirmed sub-mm galaxies in the HerBS-70 system have relatively short gas depletion times (80 − 500 Myr), indicating the onset of quenching for this protocluster core due to the depletion of gas. The dark matter halo mass of the HerBS-70 system is estimated around 5 × 1013 M⊙, with a projected current-day mass of 1015 M⊙, similar to the local Virgo and Coma clusters. These observations support the claim that DSFGs, in particular the ones with observed multiplicity, can trace cosmic overdensities

Star formation in the centre of NGC 1808 as observed by ALMA

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of 85.69 and 99.02 GHz continuum emission and H42α and H40α lines emission from the central 1~kpc of NGC 1808. These forms of emission are tracers of photoionizing stars but unaffected by dust obscuration that we use to test the applicability of other commonly star formation metrics. An analysis of the spectral energy distributions shows that free-free emission contributes about 60 to 90 per cent of the continuum emission in the 85-100 GHz frequency range, dependent on the region. The star formation rate (SFR) derived from the ALMA free-free emission is 3.1±0.3~M⊙~yr−1. This is comparable to the SFRs measured from the infrared emission, mainly because most of the bolometric energy from the heavily obscured region is emitted as infrared emission. The radio 1.5~GHz emission yields a SFR 25 per cent lower than the ALMA value, probably because of the diffusion of the electrons producing the synchrotron emission beyond the star-forming regions. The SFRs measured from the extinction-corrected Hα line emission are about 40 to 65 per cent of the SFR derived from the ALMA data, likely because this metric was not calibrated for high extinction regions. Some SFRs based on extinction-corrected ultraviolet emission are similar to those from ALMA and infrared data, but given that the ultraviolet terms in the extinction correction equations are very small, these metrics seem inappropriate to apply to this dusty starburst

ALMA &lt;sup&gt;13&lt;/sup&gt;CO(J = 1 − 0) Observations of NGC 604 in M33: Physical properties of molecular clouds

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of 13CO(J=1−0) line and 104 GHz continuum emission from NGC 604, a giant HII region (GHR) in the nearby spiral galaxy M33. Our high spatial resolution images ( 3.2"× 2.4", corresponding to 13×10 pc physical scale) allow us to detect fifteen molecular clouds. We find spatial offsets between the 13CO and 104 GHz continuum emission and also detect continuum emission near the centre of the GHR. The identified molecular clouds have sizes ranging from 5-21 pc, linewidths of 0.3-3.0 kms−1 and luminosity-derived masses of (0.4-80.5) ×103 M⨀. These molecular clouds are in near virial equilibrium, with a spearman correlation coefficient of 0.98. The linewidth-size relationship for these clouds is offset from the corresponding relations for the Milky Way and for NGC 300, although this may be an artefact of the dendrogram process

HELGA VI. Giant molecular cloud associations in M31

VizieR online Data Catalogue associated with article published in journal Astronomical Journal (AAS) with title 'The Herschel Exploitation of Local Galaxy Andromeda (HELGA). VI. The distribution and properties of molecular cloud associations in M31.' (bibcode: 2015ApJ...798...58K