Kepler-7b is to date the only exoplanet for which clouds have been inferred from the optical phase curve—from visible-wavelength whole-disk brightness measurements as a function of orbital phase. ...Added to this, the fact that the phase curve appears dominated by reflected starlight makes this close-in giant planet a unique study case. Here we investigate the information on coverage and optical properties of the planet clouds contained in the measured phase curve. We generate cloud maps of Kepler-7b and use a multiple-scattering approach to create synthetic phase curves, thus connecting postulated clouds with measurements. We show that optical phase curves can help constrain the composition and size of the cloud particles. Indeed, model fitting for Kepler-7b requires poorly absorbing particles that scatter with low-to-moderate anisotropic efficiency, conclusions consistent with condensates of silicates, perovskite, and silica of submicron radii. We also show that we are limited in our ability to pin down the extent and location of the clouds. These considerations are relevant to the interpretation of optical phase curves with general circulation models. Finally, we estimate that the spherical albedo of Kepler-7b over the Kepler passband is in the range 0.4–0.5.
Abstract
We describe a
Herschel Space Observatory
194–671
μ
m spectroscopic survey of a sample of 121 local luminous infrared galaxies and report the fluxes of the CO
J
to
J
–1 rotational transitions ...for
, the N
ii
205
μ
m line, the C
i
lines at 609 and 370
μ
m, as well as additional and usually fainter lines. The CO spectral line energy distributions (SLEDs) presented here are consistent with our earlier work, which was based on a smaller sample, that calls for two distinct molecular gas components in general: (i) a cold component, which emits CO lines primarily at
J
≲ 4 and likely represents the same gas phase traced by CO (1−0), and (ii) a warm component, which dominates over the mid-
J
regime (4 <
J
≲ 10) and is intimately related to current star formation. We present evidence that the CO line emission associated with an active galactic nucleus is significant only at
J
> 10. The flux ratios of the two C
i
lines imply modest excitation temperatures of 15–30 K; the C
i
370
μ
m line scales more linearly in flux with CO (4−3) than with CO (7−6). These findings suggest that the C
i
emission is predominantly associated with the gas component defined in (i) above. Our analysis of the stacked spectra in different far-infrared (FIR) color bins reveals an evolution of the SLED of the rotational transitions of
vapor as a function of the FIR color in a direction consistent with infrared photon pumping.
Aims. We analyze the applicability of far-infrared fine-structure lines Cii 158 μm, Oi 63 μm, and Oiii 88 μm to reliably trace the star formation rate (SFR) in a sample of low-metallicity dwarf ...galaxies from the Herschel Dwarf Galaxy Survey and, furthermore, extend the analysis to a broad sample of galaxies of various types and metallicities in the literature. Methods. We study the trends and scatter in the relation between the SFR (as traced by GALEX FUV and MIPS 24 μm) and far-infrared line emission, on spatially resolved and global galaxy scales, in dwarf galaxies. We assemble far-infrared line measurements from the literature and infer whether the far-infrared lines can probe the SFR (as traced by the total infrared luminosity) in a variety of galaxy populations. Results. In metal-poor dwarfs, the Oi63 and Oiii88 lines show the strongest correlation with the SFR with an uncertainty on the SFR estimates better than a factor of 2, while the link between Cii emission and the SFR is more dispersed (uncertainty factor of 2.6). The increased scatter in the SFR–LCII relation toward low metal abundances, warm dust temperatures, and large filling factors of diffuse, highly ionized gas suggests that other cooling lines start to dominate depending on the density and ionization state of the gas. For the literature sample, we evaluate the correlations for a number of different galaxy populations. The Cii and Oi63 lines are considered to be reliable SFR tracers in starburst galaxies, recovering the star formation activity within an uncertainty of factor 2. For sources with composite and active galactic nucleus (AGN) classifications, all three FIR lines can recover the SFR with an uncertainty factor of 2.3. The SFR calibrations for ultra-luminous infrared galaxies (ULIRGs) are similar to starbursts/AGNs in terms of scatter but offset from the starburst/AGN SFR relations because of line deficits relative to their total infrared luminosity. While the number of detections of the FIR fine-structure lines is still very limited at high redshift for Oi63 and Oiii88, we provide an SFR calibration for Cii.
We used the SPIRE/FTS instrument aboard the Herschel Space Observatory to obtain the Spectral Line Energy Distributions (SLEDs) of CO from J = 4-3 to J = 13-12 of Arp 193 and NGC 6240, two classical ...merger/starbursts selected from our molecular line survey of local Luminous Infrared Galaxies (L sub(IR) > or =, slanted 10 super(11) L sub(middot in circle)). We find the two CO SLEDs strongly diverging from J = 4-3 onward, with NGC 6240 having a much higher CO line excitation than Arp 193, despite their similar low-J CO SLEDs and L sub(FIR)/L sub(CO,1-0), L sub(HCN)/L sub(CO) (J = 1-0) ratios (proxies of star formation efficiency and dense gas mass fraction). In Arp 193, one of the three most extreme starbursts in the local universe, the molecular SLEDs indicate a small amount (~5%-15%) of dense gas (n > or =, slanted 10 super(4) cm super(-3)) unlike NGC 6240 where most of the molecular gas (~60%-70%) is dense (n ~ (10 super(4)-10 super(5)) cm super(-3)).
We present the submillimeter spectra from 450 to 1550 GHz of 11 nearby active galaxies observed with the SPIRE Fourier Transform Spectrometer (SPIRE/FTS) on board Herschel. We detect CO transitions ...from J sub(up) = 4 to 12, as well as the two CI fine structure lines at 492 and 809 GHz and the NII1461 GHz line. We used radiative transfer models to analyze the observed CO spectral line energy distributions. The FTS CO data were complemented with ground-based observations of the low-J CO lines. We found that the warm molecular gas traced by the mid-J CO transitions has similar physical conditions (n sub(H2) ~ 10 super(3.2)-10 super(3.9) cm super(-3) and T sub(kin) ~ 300-800 K) in most of our galaxies. Furthermore, we found that this warm gas is likely producing the mid-IR rotational H sub(2) emission. We could not determine the specific heating mechanism of the warm gas, however, it is possibly related to the star formation activity in these galaxies. Our modeling of the CI emission suggests that it is produced in cold (T sub(kin) < 30 K) and dense (n sub(H2) > 10 super(3) cm super(-3)) molecular gas. Transitions of other molecules are often detected in our SPIRE/FTS spectra. The HF J = 1-0 transition at 1232 GHz is detected in absorption in UGC 05101 and in emission in NGC 7130. In the latter, near-infrared pumping, chemical pumping, or collisional excitation with electrons are plausible excitation mechanisms likely related to the active galactic nucleus of this galaxy. In some galaxies, few H sub(2)O emission lines are present. Additionally, three OH+ lines at 909, 971, and 1033 GHz are identified in NGC 7130.
We report on new sensitive CO J = 6-5 line observations of several luminous infrared galaxies (LIRGs; L {sub IR}(8-1000 {mu}m) {approx}> 10{sup 11} L {sub sun}), 36% (8/22) of them ultraluminous ...infrared galaxies (ULIRGs) (L {sub IR}>10{sup 12} L {sub sun}), and two powerful local active galactic nuclei (AGNs)-the optically luminous QSO PG 1119+120 and the powerful radio galaxy 3C 293-using the James Clerk Maxwell Telescope on Mauna Kea in Hawaii. We combine these observations with existing low-J CO data and dust emission spectral energy distributions in the far-infrared-submillimeter from the literature to constrain the properties of the star-forming interstellar medium (ISM) in these systems. We then build the first local CO spectral line energy distributions (SLEDs) for the global molecular gas reservoirs that reach up to high J-levels. These CO SLEDs are neither biased by strong lensing (which affects many of those constructed for high-redshift galaxies), nor suffer from undersampling of CO-bright regions (as most current high-J CO observations of nearby extended systems do). We find: (1) a significant influence of dust optical depths on the high-J CO lines, suppressing the J = 6-5 line emission in some of the most IR-luminous LIRGs, (2) low global CO line excitation possible even in vigorously star-forming systems, (3) the first case of a shock-powered high-excitation CO SLED in the radio galaxy 3C 293 where a powerful jet-ISM interaction occurs, and (4) unusually highly excitated gas in the optically powerful QSO PG 1119+120. In Arp 220 and possibly other (U)LIRGs very faint CO J = 6-5 lines can be attributed to significant dust optical depths at short submillimeter wavelengths immersing those lines in a strong dust continuum, and also causing the C{sup +} line luminosity deficit often observed in such extreme starbursts. Re-analysis of the CO line ratios available for submillimeter galaxies suggests that similar dust opacities also may be present in these high-redshift starbursts, with genuinely low excitation of large amounts of SF-quiescent gas being the only other possibility for their often low CO (high-J)/(low-J) line ratios. We then present a statistical method of separating these two almost degenerate possibilities, and show that high dust optical depths at submillimeter wavelengths can impede the diagnostic potential of submillimeter/IR lines (e.g., starbursts versus AGNs as gas excitation agents), which is of particular importance for the upcoming observations of the Herschel Space Observatory and the era of ALMA.
Star formation and accretion onto supermassive black holes in the nuclei of galaxies are the two most energetic processes in the universe, producing the bulk of the observed emission throughout its ...history. We simulated the luminosity functions of star-forming and active galaxies for spectral lines that are thought to be good spectroscopic tracers of either phenomenon, as a function of redshift. We focused on the infrared (IR) and submillimeter domains, where the effects of dust obscuration are minimal. Using three different and independent theoretical models for galaxy formation and evolution, constrained by multi-wavelength luminosity functions, we computed the number of star-forming and active galaxies per IR luminosity and redshift bin. We converted the continuum luminosity counts into spectral line counts using relationships that we calibrated on mid- and far-IR spectroscopic surveys of galaxies in the local universe. Our results demonstrate that future facilities optimized for survey-mode observations, i.e., the Space Infrared telescope for Cosmology and Astrophysics and the Cerro Chajnantor Atacama Telescope, will be able to observe thousands of z > 1 galaxies in key fine-structure lines, e.g., SiII, OI, OIII, CIII, in a half-square-degree survey, with 1 hr integration time per field of view. Fainter lines such as OIV, NeV, and H sub(2) (0-0)S1 will be observed in several tens of bright galaxies at 1 < z < 2, while diagnostic diagrams of active nucleus versus star formation activity will be feasible even for normal z ~ 1 galaxies. We discuss the new parameter space that these future telescopes will cover and that strongly motivates their construction.
We present a broadband waveguide ortho-mode transducer for the WR10 band that was designed for CLOVER, an astrophysics experiment aiming to characterize the polarization of the cosmic microwave ...background radiation. The design, based on a turnstile junction, was manufactured and then tested using a millimeter-wave vector network analyzer. The average measured return loss and isolation were -22 dB and -45 dB, respectively, across the entire WR10 band
We present results of the first systematic search for submillimetre (submm) continuum emission from z∼ 2, radio-quiet, optically-luminous (MB < −27.5) quasars, using the SCUBA array camera on the ...James Clerk Maxwell Telescope (JCMT). We have observed a homogeneous sample of 57 quasars in the redshift range 1.5 < z < 3.0— the epoch during which the comoving density of luminous active galactic nuclei (AGN) peaks — to make a systematic comparison with an equivalent sample at high redshift (z > 4; Paper I). The target sensitivity of the survey, 3σ = 10 mJy at 850 μm, was chosen to enable efficient identification of bright submm sources, suitable for detailed follow-up. Nine targets are detected with 3σ significance or greater, with fluxes in the range 7–17 mJy. Although the detection rate above 10 mJy is lower than that of the z > 4 survey, the weighted mean flux of the undetected sources, 1.9 ± 0.4 mJy, is similar to that at z > 4 (2.0 ± 0.6 mJy). The statistical significance of trends is analysed, and it is found that: (i) within the limited optical luminosity range studied, there is no strong evidence for a correlation between submm and optical luminosity; (ii) there is a suggestion of a variation of submm detectability with redshift, but that this is consistent with the K-correction of a characteristic far-infrared spectrum.
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