We have measured the mass of metals in the molecular gas in 13 submillimetre galaxies at z~4 in which the gas, based on previous observations, lies in a cold rotating disk. We measured the metal ...masses using either the submillimetre line or continuum emission from three tracers of the overall metal content - carbon atoms, carbon monoxide molecules and dust grains - using the first simultaneous calibration of all three tracers (Dunne et al. 2022). We obtain very similar mass estimates from the different tracers, which are similar to the entire metal content of a present-day massive early-type galaxy. We used the dynamical masses of these galaxies to set an upper limit on the mass of the molecular gas in each galaxy, allowing us to set a lower limit on the metal abundance in the gas, finding values for many of the galaxies well above the solar value. We use chemical evolution models to show that such high metal masses and abundances are what is expected shortly after the formation of a galaxy for a top-heavy IMF. We suggest a scenario for galaxy evolution in which massive galaxies reach a high metal abundance during their formation phase, which is then gradually reduced by dry mergers with lower mass galaxies. We use the chemical-evolution models to show that the metals in the outflows from massive early-type galaxies in their formation phase can quantitatively explain the long-standing puzzle that approximately 75% of the metals in clusters of galaxies is in the intracluster gas rather than in the galaxies.
This is the second in a series of papers presenting results from the SCUBA Local Universe Galaxy Survey. In our first paper we provided 850-micron flux densities for 104 galaxies selected from the ...IRAS Bright Galaxy Sample and we found that the 60-, 100-micron (IRAS) and 850-micron (SCUBA) fluxes could be adequately fitted by emission from dust at a single temperature. In this paper we present 450-micron data for the galaxies. With the new data, the spectral energy distributions of the galaxies can no longer be fitted with an isothermal dust model - two temperature components are now required. Using our 450-micron data and fluxes from the literature, we find that the 450/850-micron flux ratio for the galaxies is remarkably constant, and this holds from objects in which the star formation rate is similar to our own Galaxy, to ultraluminous infrared galaxies (ULIRGs) such as Arp 220. The only possible explanation for this is if the dust emissivity index for all of the galaxies is about 2 and the cold dust component has a similar temperature in all galaxies (Tc about 20-21 K). The 60-micron luminosities of the galaxies were found to depend on both the dust mass and the relative amount of energy in the warm component, with a tendency for the temperature effects to dominate at the highest L60. (Author)
Many of the faint submm sources uncovered by deep SCUBA surveys still remain unidentified at most, if not all, other wavelengths. The most successful method so far of obtaining accurate positions and ...hence allowing more secure identifications has been to use centimetre-wavelength imaging with the VLA. This has led to a tempting approach for obtaining redshift estimates for this population by Carilli & Yun, which relies on the tight FIR-radio relationship and takes advantage of the steep spectral slope in the submm. In this paper we use the submm data from the SCUBA Local Universe Galaxy Survey (SLUGS) to estimate the usefulness of, and the uncertainties in, the radio-submm redshift estimator. If the submm-radio spectral index were correlated with either dust temperature or 850-μm luminosity, this method could produce biased redshift estimates for 850-μm selected galaxies. We find, however, that within SLUGS, these correlations are not significant. The ratio of 850-μm to 1.4-GHz flux is found to decrease with increasing radio and FIR luminosity, and we propose that this is due to a component of the dust not associated with recent star formation, but which is instead heated to 15–20 K by the general interstellar radiation field.
Iron needles in supernova remnants? Gomez (née Morgan), Haley L.; Dunne, Loretta; Eales, Stephen A. ...
Monthly notices of the Royal Astronomical Society,
08/2005, Letnik:
361, Številka:
3
Journal Article
We present optical, near-infrared (IR) and radio observations of the 3-hour field of the Canada–UK Deep Submillimetre Survey (CUDSS). Of the 27 submillimetre sources in the field, nine have secure ...identifications with either a radio source or a near-IR source. We show that the percentage of sources with secure identifications in the CUDSS is consistent with that found for the bright ‘8-mJy’ submillimetre survey, once allowance is made for the different submillimetre and radio flux limits. Of the 14 secure identifications in the two CUDSS fields, eight are very red objects (VROs) or extremely red objects (EROs), five have colours typical of normal galaxies and one is a radio source that has not yet been detected at optical/near-IR wavelengths. 11 of the identifications have optical/near-IR structures which are either disturbed or have some peculiarity that suggests that the host galaxy is part of an interacting system. One difference between the CUDSS results and the results from the 8-mJy survey is the large number of low-redshift objects in the CUDSS. We give several arguments why these are genuine low-redshift submillimetre sources rather than being gravitational lenses that are gravitationally amplifying a high-z submillimetre source. We construct a K–z diagram for various classes of high-redshift galaxy and show that the SCUBA galaxies are on average less luminous than classical radio galaxies, but are very similar in both their optical/IR luminosities and their colours to the host galaxies of the radio sources detected in μJy radio surveys.
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