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Register a new userA puzzling non-detection of [O III] and [C II] from a $z approx 7.7$ galaxy observed with ALMA
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Characterizing the galaxy population in the early Universe holds the key to understanding the evolution of these objects and the role they played in cosmic reionization. However, the number of observations at the very highest redshifts are to date, few. In order to shed light on the properties of galaxies in the high-redshift Universe and their interstellar media, we observe the Lyman-$alpha$ emitting galaxy z7_GSD_3811 at $z=7.664$ with band 6 and 8 at the Atacama Large Millimeter/submillimeter Array (ALMA). We target the far-infrared [O III] 88 $mu m$, [C II] 158 $mu m$ emission lines and dust continuum in the star-forming galaxy z7_GSD_3811 with ALMA. We combine these measurements with earlier observations in the rest-frame ultraviolet (UV) in order to characterize the object, and compare results to those of earlier studies observing [O III] and [C II] emission in high-redshift galaxies. The [O III] 88 $mu m$ and [C II] 158 $mu m$ emission lines are undetected at the position of z7_GSD_3811, with $3sigma$ upper limits of $1.6 times 10^{8} L_{odot}$ and $4.0 times 10^{7} L_{odot}$, respectively. We do not detect any dust continuum in band 6 nor band 8. The measured rms in the band 8 and band 6 continuum is 26 and 9.9 $mu Jy beam^{-1}$, respectively. Similar to several other high-redshift galaxies, z7_GSD_3811 exhibits low [C II] emission for its star formation rate compared to local galaxies. Furthermore, our upper limit on the [O III] line luminosity is lower than all the previously observed [O III] lines in high-redshift galaxies with similar ultraviolet luminosities. Our ALMA band 6 and 8 dust continuum observations imply that z7_GSD_3811 likely has a low dust content, and our non-detections of the [O III] and [C II] lines could indicate that z7_GSD_3811 has a low metallicity ($Z lesssim 0.1 Z_{odot}$).
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The circumnuclear region of M31, consisting of multiphase interstellar medium, provides a close-up view of the interaction of the central supermassive black hole and surrounding materials. Far-infrared (FIR) line structure lines and their flux ratios can be used as diagnostics of physical properties of the neutral gas in this region. Here we present the first FIR spectroscopic mapping of the circumnuclear region of M31 in [C ii] 158 um, [O i] 63 um and [O iii] 88 um lines with the Herschel Space Observatory, covering a ~500 x 500 pc (2 x 2) field. Significant emissions of all three lines are detected along the so-called nuclear spiral across the central kpc of M31. The velocity field under a spatial resolution of ~50 pc of the three lines are in broad consistency and also consistent with previous CO(3-2) line observations in the central region. Combined with existing [C ii] and CO(3-2) observations of five other fields targeting on the disk, we derived the radial distribution of [C ii]/CO(3-2) flux ratio, and found that this ratio is higher in the center than the disk, indicating a low gas density and strong radiation field in the central region. We also found that the [C ii]/FIR ratio in the central region is 5.4 (+-0.8) x 10^-3, which exhibits an increasing trend with the galactocentric radius, suggesting an increasing contribution from old stellar population to dust heating towards the center.
Our objectives are to determine the properties of the interstellar medium (ISM) and of star-formation in typical star-forming galaxies at high redshift. Following up on our previous multi-wavelength observations with HST, Spitzer, Herschel, and the Plateau de Bure Interferometer (PdBI), we have studied a strongly lensed z=2.013 galaxy, the arc behind the galaxy cluster MACS J0451+0006, with ALMA to measure the [CII] 158 micron emission line, one of the main coolants of the ISM. [CII] emission from the southern part of this galaxy is detected at 10 $sigma$. Taking into account strong gravitational lensing, which provides a magnification of $mu=49$, the intrinsic lensing-corrected [CII]158 micron luminosity is $L(CII)=1.2 times 10^8 L_odot$. The observed ratio of [CII]-to-IR emission, $L(CII)/L(FIR) approx (1.2-2.4) times 10^{-3}$, is found to be similar to that in nearby galaxies. The same also holds for the observed ratio $L(CII)/L(CO)=2.3 times 10^3$, which is comparable to that of star-forming galaxies and active galaxy nuclei (AGN) at low redshift. We utilize strong gravitational lensing to extend diagnostic studies of the cold ISM to an order of magnitude lower luminosity ($L(IR) sim (1.1-1.3) times 10^{11} L_odot$) and SFR than previous work at high redshift. While larger samples are needed, our results provide evidence that the cold ISM of typical high redshift galaxies has physical characteristics similar to normal star forming galaxies in the local Universe.
We present new Atacama Large Millimeter/submillimeter Array Band 7 observational results of a Lyman break galaxy at $ z=7.15 $, B14-65666 (Big Three Dragons), which is an object detected in [OIII] 88 $rm{mu m}$, [CII] 158 $rm{mu m}$, and dust-continuum emission during the epoch of reionization. Our targets are the [NII] 122 $rm{mu m}$ fine-structure emission line and underlying 120 $rm{mu m}$ dust continuum. The dust continuum is detected with a $ sim $19$ sigma $ significance. From far-infrared spectral energy distribution sampled at 90, 120, and 160 $rm{mu m}$, we obtaine a best-fit dust temperature of $ 40 $ K ($ 79 $ K) and an infrared luminosity of $ log_{10}(L_{rm IR}/{rm L}_odot)=11.6$ ($12.1$) at the emissivity index $ beta = 2.0 $ (1.0). The [NII] 122 $rm{mu m}$ line is not detected. The 3$ sigma $ upper limit of the [NII] luminosity is $ 8.1 times 10^7 {rm L}_odot$. From the [NII], [OIII], and [CII] line luminosities, we use the Cloudy photoionization code to estimate nebular parameters as functions of metallicity. If the metallicity of the galaxy is high ($ Z > 0.4 {rm Z}_odot$), the ionization parameter and hydrogen density are $ log_{10} U simeq -2.7pm0.1$ and $ n_text{H} simeq 50$-$250 {rm cm}^{-3}$, respectively, which are comparable to those measured in low-redshift galaxies. The nitrogen-to-oxygen abundance ratio, $rm{N/O}$, is constrained to be sub-solar. At $ Z < 0.4 {rm Z}_odot$, the allowed $ U $ drastically increases as the assumed metallicity decreases. For high ionization parameters, the $rm{N/O}$ constraint becomes weak. Finally, our Cloudy models predict the location of B14-65666 on the BPT diagram, thereby allowing a comparison with low-redshift galaxies.
We take advantage of new 100-hour Spitzer/IRAC observations available for MACS0647-JD, a strongly lensed $zapprox11$ galaxy candidate, to provide improved constraints on its physical properties. Probing the physical properties of galaxies at $z>8$ is challenging due to the inherent faintness of such sources and the limited wavelength coverage available. Thanks to the high $approx$2-6$times$ lensing magnification of the multiple images of MACS0647-JD, we can use the sensitive Spitzer/IRAC data to probe the rest-frame optical fluxes of MACS0647-JD and investigate its physical properties including the age and the stellar mass. In deriving Spitzer/IRAC fluxes for MACS0647-JD, great care is taken in coping with the impact of three bright ($approx$8-16 mag) stars in our field to ensure robust results. Assuming a constant star formation rate, the age, stellar mass, and rest-frame UV slope we estimate for MACS0647-JD based on a stack of the photometry are log$_{10}$(age/yr) = 8.6$^{+0.1}_{-2.1}$, log$_{10}$(M$_{*}$/M$_{odot}$) = 9.1$^{+0.2}_{-1.4}$, and $beta = -$1.3$pm$0.6, respectively. We compare our results with expectations from the EAGLE simulation and find that MACS0647-JD has properties consistent with corresponding to the most massive and rapidly star-forming galaxies in the simulation. We also find that its radius, 105$pm$28 pc, is a factor of $approx$2 smaller than the mean size in a separate simulation project DRAGONS. Interestingly enough, the observed size is similar to the small sizes seen in very low-luminosity $zapprox$6-10 galaxies behind lensing clusters.
Emission signatures from galactic winds provide an opportunity to directly map the outflowing gas, but this is traditionally challenging because of the low surface brightness. Using deep observations (27 hours) of the Hubble Deep Field South from the Multi Unit Spectroscopic Explorer (MUSE) instrument, we identify signatures of an outflow in both emission and absorption from a spatially resolved galaxy at z = 1.29 with a stellar mass M* = 8 x 10^9 Msun, star formation rate SFR = 77 Msun/yr, and star formation rate surface brightness 1.6 Msun/kpc^2 within the [OII] half-light radius R_1/2,[OII] = 2.76 +- 0.17 kpc. From a component of the strong resonant MgII and FeII absorptions at -350 km/s, we infer a mass outflow rate that is comparable to the star formation rate. We detect non-resonant FeII* emission, at lambda 2626, 2612, 2396, and 2365, at 1.2-2.4-1.5-2.7 x 10^-18 egs s-1 cm-2 respectively. These flux ratios are consistent with the expectations for optically thick gas. By combining the four non-resonant FeII* emission lines, we spatially map the FeII* emission from an individual galaxy for the first time. The FeII* emission has an elliptical morphology that is roughly aligned with the galaxy minor kinematic axis, and its integrated half-light radius R_1/2,FeII* = 4.1 +- 0.4 kpc is 50% larger than the stellar continuum (R_1/2,* = 2.34 +- 0.17 kpc) or the [OII] nebular line. Moreover, the FeII* emission shows a blue wing extending up to -400 km/s, which is more pronounced along the galaxy minor kinematic axis and reveals a C-shaped pattern in a p-v diagram along that axis. These features are consistent with a bi-conical outflow.
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