We present a first analysis of deep 24 km observations with the Spitzer Space Telescope of a sample of nearly 1500 galaxies in a thin redshift slice, 0.65 , z < 0.75. We combine the infrared data ...with redshifts, rest-frame luminosities, and colors from COMBO-17 and with morphologies from Hubble Space Telescope images collected by the Galaxy Evolution from Morphology and SEDs (GEMS) and Great Observatories Origins Deep Survey (GOODS) projects. To characterize the decline in star formation rate (SFR) since z 6 0.7, we estimate the total thermal IR luminosities, SFRs, and stellar masses for the galaxies in this sample. At z 6 0.7, nearly 40% of intermediate- and high-mass galaxies (with stellar masses .2 x 10 super(10) M sub( )) are undergoing a period of intense star formation above their past-averaged SFR. In contrast, less than 1% of equally massive galaxies in the local universe have similarly intense star formation activity. Morphologically undisturbed galaxies dominate the total infrared luminosity density and SFR density: at z 6 0.7, more than half of the intensely star-forming galaxies have spiral morphologies, whereas less than 630% are strongly interacting. Thus, a decline in major merger rate is not the underlying cause of the rapid decline in cosmic SFR since z 6 0.7. Physical properties that do not strongly affect galaxy morphology--for example, gas consumption and weak interactions with small satellite galaxies--appear to be responsible.
To elucidate the intrinsic broadband infrared (IR) emission properties of active galactic nuclei (AGNs), we analyze the spectral energy distributions (SEDs) of 87 z 0.5 Palomar-Green (PG) quasars. ...While the Elvis AGN template with a moderate far-IR correction can reasonably match the SEDs of the AGN components in ∼60% of the sample (and is superior to alternatives such as that by Assef), it fails on two quasar populations: (1) hot-dust-deficient (HDD) quasars that show very weak emission thoroughly from the near-IR to the far-IR, and (2) warm-dust-deficient (WDD) quasars that have similar hot dust emission as normal quasars but are relatively faint in the mid- and far-IR. After building composite AGN templates for these dust-deficient quasars, we successfully fit the 0.3-500 m SEDs of the PG sample with the appropriate AGN template, an infrared template of a star-forming galaxy, and a host galaxy stellar template. 20 HDD and 12 WDD quasars are identified from the SED decomposition, including seven ambiguous cases. Compared with normal quasars, the HDD quasars have AGNs with relatively low Eddington ratios and the fraction of WDD quasars increases with AGN luminosity. Moreover, both the HDD and WDD quasar populations show relatively stronger mid-IR silicate emission. Virtually identical SED properties are also found in some quasars from z = 0.5 to 6. We propose a conceptual model to demonstrate that the observed dust deficiency of quasars can result from a change of structures of the circumnuclear tori that can occur at any cosmic epoch.
We analyze a sample of 62600 Spitzer MIPS 24 km sources brighter than 680 kJy and located in the Chandra Deep Field-South to characterize the evolution of the comoving infrared (IR) energy density of ...the universe up to z 6 1. Using published ancillary optical data, we first obtain a nearly complete redshift determination for the 24 km objects associated with R 24 mag counterparts at z 1. These sources represent 655%-60% of the total MIPS 24 km population with f sub(24)k sub(m) 80 kJy, the rest of the sample likely lying at higher redshifts. We then determine an estimate of their total IR luminosities using various libraries of IR spectral energy distributions. We find that the 24 km population at 0.5 z 1 is dominated by "luminous infrared galaxies" (i.e., 10 super(11) L sub( ), L sub(IR) , 10 super(12) L sub( )), the counterparts of which appear to be also luminous at optical wavelengths and tend to be more massive than the majority of optically selected galaxies. A significant number of fainter sources (5 x 10 super(10) L sub( )L sub(IR) , 10 super(11) L sub( ))are also detected at similar distances. We finally derive 15 km and total IR luminosity functions (LFs) up to z 6 1. In agreement with the previous results from the Infrared Space Observatory (ISO) and SCUBA and as expected from the MIPS source number counts, we find very strong evolution of the contribution of the IR-selected population with look-back time. Pure evolution in density is firmly excluded by the data, but we find considerable degeneracy between strict evolution in luminosity and a combination of increases in both density and luminosity L IR a (1 + z) super(3.2) super(+) sub(-) super(0) sub(0) super(.) sub(.) super(7) sub(2) hIR a (1 + z) super(0.7) super(+) sub(-) super(0) sub(0) super(.) sub(.) super(6) sub(2). A significant steepening of the faint-end slope of the IR luminosity function is also unlikely, as it would overproduce the faint 24 km source number counts. Our results imply that the comoving IR energy density of the universe evolves as (1 + z) super(3.9c0.4) up to z 6 1 and that galaxies luminous in the infrared (i.e., L sub(IR) . 10 super(11) L sub( )) are responsible for 70% c 15% of this energy density at z 6 1. Taking into account the contribution of the UV luminosity evolving as (1 + z)6 super(2.5), we infer that these IR-luminous sources dominate the star-forming activity beyond z 6 0.7. The uncertainties affecting these conclusions are largely dominated by the errors in the k-corrections used to convert 24 km fluxes into luminosities.
We study massive galaxies at z 6 1-3.5 using HST optical imaging, ground-based near-IR imaging, and Spitzer observations at 3-24 km. From K sub(s)-selected galaxies in the 130 arcmin super(2) GOODS-S ...field, we identify 153 distant red galaxies (DRGs) with (J-K sub(s)) sub(Vega) . 2.3. This sample is approximately complete in stellar mass for passively evolving galaxies above 10 super(11) M sub( )and z , 3. Roughly half of the DRGs are objects whose optical and near-IR rest-frame light is dominated by evolved stars combined with ongoing star formation (at z sub(med) 6 2.5), and the others are galaxies whose light is dominated by heavily reddened (A sub(1600) 4-6 mag) starbursts (at z sub(med) 6 1.7). Very few DRGs ( 10%) have no indication of current star formation. DRGs at z 6 1.5-3 with stellar masses .10 super(11) M sub( )have specific star formation rates (SFRs per unit mass) including the reradiated far-IR emission that range from 0.2 to 10 Gyr super(-1). Based on the X-ray luminosities and rest-frame near-IR colors, roughly one-quarter of the DRGs contain AGNs, implying that the growth of supermassive black holes coincides with the formation of massive galaxies. At 1.5 , z , 3, the DRGs with M. 10 super(11) M sub( )have an integrated specific SFR comparable to the global value of all galaxies. In contrast, galaxies at z 6 0.3-0.75 with M . 10 super(11) M sub( )have an integrated specific SFR less than the global value and more than an order of magnitude lower than that for massive DRGs. At z 1, lower mass galaxies dominate the overall cosmic mass assembly. This suggests that the bulk of star formation in massive galaxies occurs at early cosmic epochs and is largely complete by z 6 1.5. Further mass assembly in these galaxies takes place with low specific SFRs.
A deep ALMA image of the Hubble Ultra Deep Field Dunlop, J. S; McLure, R. J; Biggs, A. D ...
Monthly notices of the Royal Astronomical Society,
04/2017, Letnik:
466, Številka:
1
Journal Article
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Abstract
We present the results of the first, deep Atacama Large Millimeter Array (ALMA) imaging covering the full ≃4.5 arcmin2 of the Hubble Ultra Deep Field (HUDF) imaged with Wide Field Camera ...3/IR on HST. Using a 45-pointing mosaic, we have obtained a homogeneous 1.3-mm image reaching σ1.3 ≃ 35 μJy, at a resolution of ≃0.7 arcsec. From an initial list of ≃50 > 3.5σ peaks, a rigorous analysis confirms 16 sources with S
1.3 > 120 μJy. All of these have secure galaxy counterparts with robust redshifts (〈z〉 = 2.15). Due to the unparalleled supporting data, the physical properties of the ALMA sources are well constrained, including their stellar masses (M
*) and UV+FIR star formation rates (SFR). Our results show that stellar mass is the best predictor of SFR in the high-redshift Universe; indeed at z ≥ 2 our ALMA sample contains seven of the nine galaxies in the HUDF with M
* ≥ 2 × 1010 M⊙, and we detect only one galaxy at z > 3.5, reflecting the rapid drop-off of high-mass galaxies with increasing redshift. The detections, coupled with stacking, allow us to probe the redshift/mass distribution of the 1.3-mm background down to S
1.3 ≃ 10 μJy. We find strong evidence for a steep star-forming ‘main sequence’ at z ≃ 2, with SFR ∝M
* and a mean specific SFR ≃ 2.2 Gyr−1. Moreover, we find that ≃85 per cent of total star formation at z ≃ 2 is enshrouded in dust, with ≃65 per cent of all star formation at this epoch occurring in high-mass galaxies (M
* > 2 × 1010 M⊙), for which the average obscured:unobscured SF ratio is ≃200. Finally, we revisit the cosmic evolution of SFR density; we find this peaks at z ≃ 2.5, and that the star-forming Universe transits from primarily unobscured to primarily obscured at z ≃ 4.
We present infrared observations of 66 starburst galaxies over the full range of oxygen abundances observed in local star-forming galaxies, from image to 8.9. The data include imaging and ...spectroscopy from the Spitzer Space Telescope, supplemented by ground-based near-infrared imaging. We confirm a strong correlation of aromatic emission with metallicity, with a threshold at image. We show that the far-infrared color temperature of the large dust grains increases toward lower metallicity, peaking at a metallicity of 8 before turning over. We compute dust masses and compare them to H i masses from the literature to derive the ratio of atomic gas to dust, which increases by nearly 3 orders of magnitude between solar metallicity and a metallicity of 8, below which it flattens out. The abrupt change in aromatic emission at mid-infrared wavelengths thus appears to be reflected in the far-infrared properties, indicating that metallicity changes affect the composition of the full range of dust grain sizes that dominate the infrared emission. Although the great majority of galaxies show similar patterns of behavior as described above, there are three exceptions, SBS 0335-052E, Haro 11, and SHOC 391. Their infrared SEDs are dominated energetically by the mid- IR near 24 mum rather than by the 60-200 mum region. In addition, they have very weak near-infrared outputs and their SEDs are dominated by emission by dust at wavelengths as short as 1.8 mum. The latter behavior indicates that the dominant star-forming episodes in them are extremely young. The component of the ISM responsible for the usual far-infrared emission appears to be either missing or inefficiently heated in these three galaxies.
We present high-fidelity, 30 mas (200 pc) resolution ALMA rest-frame 240 m observations of cold dust emission in three typical main-sequence star-forming galaxies (SFGs) at z ∼ 3 in the Hubble ...Ultra-Deep Field (HUDF). The cold dust is distributed within the smooth disklike central regions of star formation 1-3 kpc in diameter, despite their complex and disturbed rest-frame UV and optical morphologies. No dust substructures or clumps are seen down to 1-3 yr−1 (1 ) per 200 pc beam. No dust emission is observed at the locations of UV-emitting clumps, which lie 2-10 kpc from the bulk of star formation. Clumpy substructures can contribute no more than 1%-7% of the total star formation in these galaxies (3 upper limits). The lack of star-forming substructures in our HUDF galaxies is to be contrasted with the multiple substructures characteristic of submillimeter-selected galaxies (SMGs) at the same cosmic epoch, particularly the far-IR-bright SMGs with similarly high-fidelity ALMA observations of Hodge et al. Individual star-forming substructures in these SMGs contain ∼10%-30% of their total star formation. A substructure in these SMGs is often comparably bright in the far-infrared to (or in some cases brighter than) our typical SFGs, suggesting that these SMGs originate from a class of disruptive events involving multiple objects at the scale of our HUDF galaxies. The scale of the disruptive event found in our main-sequence SFGs, characterized by the lack of star-forming substructures at our resolution and sensitivity, could be less violent, e.g., gas-rich disk instability or minor mergers.
We show that measures of star formation rates (SFRs) for infrared galaxies using either single-band 24 is a subset of m or extinction-corrected Pa alpha luminosities are consistent in the total ...infrared luminosity = L(TIR) ~ 1010 L range. MIPS 24 is a subset of m photometry can yield SFRs accurately from this luminosity upward: SFR(M yr-1) = 7.8 X 10-10 L(24 is a subset of m, L ) from L(TIR) = 5X 109 L to 1011 L and SFR = 7.8 X 10-10 L(24 is a subset of m, L )(7.76 X 10-11 L(24))0.048 for higher L(TIR). For galaxies with L(TIR) >= 1010 L , these new expressions should provide SFRs to within 0.2 dex. For L(TIR) >= 1011 L , we find that the SFR of infrared galaxies is significantly underestimated using extinction-corrected Pa alpha (and presumably using any other optical or near-infrared recombination lines). As a part of this work, we constructed spectral energy distribution templates for eleven luminous and ultraluminous purely star forming infrared galaxies and over the spectral range 0.4 is a subset of m to 30 cm. We use these templates and the SINGS data to construct average templates from 5 is a subset of m to 30 cm for infrared galaxies with L(TIR) = 5X 109 to 1013 L . All of these templates are made available online.
ABSTRACT The infrared spectral energy distributions of z 5 quasars can be reproduced by combining a low-metallicity galaxy template with a standard active galactic nucleus (AGN) template. The host ...galaxy is represented by Haro 11, a compact, moderately low metallicity, starbursting galaxy that shares typical features of high-z galaxies. For the vast majority of z 5 quasars, the AGN contribution is well modeled by a standard empirical template with the contamination of star formation in the infrared subtracted. Together, these two templates can separate the contributions from the host galaxy and the AGN even in the case of limited data points, given that this model has only two free parameters. Using this method, we reanalyze 69 z 5 quasars with extensive Herschel observations and derive their AGN luminosities LAGN infrared luminosities from star formation and corresponding star formation rates ( ). The average infrared luminosity from star formation and the average total AGN luminosity of the z 5 quasar sample follow the correlation defined by quasars at z < 2.6. We assume that these quasar host galaxies maintain a constant average SFR (∼620 M yr−1) during their mass assembly and estimate the stellar mass that could form prior to z ∼ 5−6 to be Combining with the black hole (BH) mass measurements, this stellar mass is adequate to establish a BH-galaxy mass ratio at 0.1%-1%, consistent with the local relation.
Abstract We demonstrate an approach to determine spectral energy distribution (SED) templates that are accurate to the 1% level from the visible through the infrared for nearby (unextincted) ...solar-type stars. Our approach is based only on measurements of T eff , log( g ), and M/H and the use of standard theoretical SED models. The success of this approach confirms that the existing absolute calibration is likely to be accurate to this level throughout this spectral range. We then demonstrate how to measure and correct for extinction, allowing extension of this calibration approach to faint levels (and more distant stars). We provide template SEDs in digital form for 11 G-dwarf stellar calibrators.
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