Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userBig Three Dragons: A [N II] 122 $mu$m Constraint and New Dust-continuum Detection of A $z = 7.15$ Bright Lyman Break Galaxy with ALMA
197
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
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.
rate research
Read More
We present new ALMA observations and physical properties of a Lyman Break Galaxy at z=7.15. Our target, B14-65666, has a bright ultra-violet (UV) absolute magnitude, $M_{rm UV}approx-22.4$, and has been spectroscopically identified in Ly$alpha$ with a small rest-frame equivalent width of $approx4$ AA. Previous HST image has shown that the target is comprised of two spatially separated clumps in the rest-frame UV. With ALMA, we have newly detected spatially resolved [OIII] 88 $mu$m, [CII] 158 $mu$m, and their underlying dust continuum emission. In the whole system of B14-65666, the [OIII] and [CII] lines have consistent redshifts of $7.1520pm0.0003$, and the [OIII] luminosity, $(34.4pm4.1)times10^{8}L_{rm odot}$, is about three times higher than the [CII] luminosity, $(11.0pm1.4)times10^{8}L_{rm odot}$. With our two continuum flux densities, the dust temperature is constrained to be $T_{rm d}approx50-60$ K under the assumption of the dust emissivity index of $beta_{rm d}=2.0-1.5$, leading to a large total infrared luminosity of $L_{rm TIR}approx1times10^{12}L_{rm odot}$. Owing to our high spatial resolution data, we show that the [OIII] and [CII] emission can be spatially decomposed into two clumps associated with the two rest-frame UV clumps whose spectra are kinematically separated by $approx200$ km s$^{-1}$. We also find these two clumps have comparable UV, infrared, [OIII], and [CII] luminosities. Based on these results, we argue that B14-65666 is a starburst galaxy induced by a major-merger. The merger interpretation is also supported by the large specific star-formation rate (defined as the star-formation rate per unit stellar mass), sSFR$=260^{+119}_{-57}$ Gyr$^{-1}$, inferred from our SED fitting. Probably, a strong UV radiation field caused by intense star formation contributes to its high dust temperature and the [OIII]-to-[CII] luminosity ratio.
We report on the detection of the [CII] 157.7 $mu$m emission from the Lyman break galaxy (LBG) MACS0416_Y1 at z = 8.3113, by using the Atacama Large Millimeter/submillimeter Array (ALMA). The luminosity ratio of [OIII] 88 $mu$m (from previous campaigns) to [CII] is 9.31 $pm$ 2.6, indicative of hard interstellar radiation fields and/or a low covering fraction of photo-dissociation regions. The emission of [CII] is cospatial to the 850 $mu$m dust emission (90 $mu$m rest-frame, from previous campaigns), however the peak [CII] emission does not agree with the peak [OIII] emission, suggesting that the lines originate from different conditions in the interstellar medium. We fail to detect continuum emission at 1.5 mm (160 $mu$m rest-frame) down to 18 $mu$Jy (3$sigma$). This nondetection places a strong limit on the dust spectrum, considering the 137 $pm$ 26 $mu$Jy continuum emission at 850 $mu$m. This suggests an unusually warm dust component (T $>$ 80 K, 90% confidence limit), and/or a steep dust-emissivity index ($beta_{rm dust}$ $>$ 2), compared to galaxy-wide dust emission found at lower redshifts (typically T $sim$ 30 - 50 K, $beta_{rm dust}$ $sim$ 1 - 2). If such temperatures are common, this would reduce the required dust mass and relax the dust production problem at the highest redshifts. We therefore warn against the use of only single-wavelength information to derive physical properties, recommend a more thorough examination of dust temperatures in the early Universe, and stress the need for instrumentation that probes the peak of warm dust in the Epoch of Reionization.
We report the study of an Einstein Cross configuration first identified in a set of HST images by Cerny et al. 2018. Deep spectroscopic observations obtained at the Spanish 10.4m GTC telescope, allowed us to demonstrate the lens nature of the system, that consists of a Lyman-break galaxy, not a QSO as is usually the case, at z = 3.03 lensed by a galaxy at z=0.556. Combining the new spectroscopy with the archival HST data, it turns out that the lens is an elliptical galaxy with M_V =-21.0, effective radius 2.8 kpc and stellar velocity dispersion sigma=208+-39 km/sec. The source is a Lyman break galaxy with Ly_alpha luminosity ~L* at that redshift. From the modeling of the system, performed by assuming a singular isothermal ellipsoid (SIE) with external shear, we estimate that the flux source is magnified about 4.5 times, and the velocity dispersion of the lens is sigma_SIE=197.9-1.3+2.6 km/s, in good agreement with the value derived spectroscopically. This is the second case known of an Einstein cross of a Lyman-break galaxy.
We present bright [CII] 158 $mu$m line detections from a strongly magnified and multiply-imaged ($musim20-160$) sub-$L^{*}$ ($M_{rm UV}$ = $-19.75^{+0.55}_{-0.44}$) Lyman-break galaxy (LBG) at $z=6.0719pm0.0004$ from the ALMA Lensing Cluster Survey (ALCS). Emission lines are identified at 268.7 GHz at $geq$ 8$sigma$ exactly at positions of two multiple images of the LBG behind the massive galaxy cluster RXCJ0600$-$2007. Our lens models, updated with the latest spectroscopy from VLT/MUSE, indicate that a sub region of the LBG crosses the caustic and is lensed into a long ($sim6$) arc with a local magnification of $musim 160$, for which the [CII] line is also significantly detected. The source-plane reconstruction resolves the interstellar medium (ISM) structure, showing that the [CII] line is co-spatial with the rest-frame UV continuum at the scale of $sim$300 pc. The [CII] line properties suggest that the LBG is a rotation-dominated system whose velocity gradient explains a slight difference of redshifts between the whole LBG and its sub region. The star formation rate (SFR)-$L_{rm [CII]}$ relations from the sub to the whole regions of the LBG are consistent with those of local galaxies. We evaluate the lower limit of the faint-end of the [CII] luminosity function at $z=6$, and find that it is consistent with predictions from semi analytical models and from the local SFR-$L_{rm [CII]}$ relation with a SFR function at $z=6$. These results imply that the local SFR-$L_{rm [CII]}$ relation is universal for a wide range of scales including the spatially resolved ISM, the whole region of galaxy, and the cosmic scale, even in the epoch of reionization.
We report the first detection obtained with ALMA of the [N II] 122$mu$m line emission from a galaxy group BRI 1202-0725 at $z=4.69$ consisting of a QSO and a submilimeter-bright galaxy (SMG). Combining with a detection of [N II] 205$mu$m line in both galaxies, we constrain the electron densities of the ionized gas based on the line ratio of [NII]122/205. The derived electron densities are $26^{+12}_{-11}$ and $134^{+50}_{-39}$ cm$^{-3}$ for the SMG and the QSO, respectively. The electron density of the SMG is similar to that of the Galactic Plane and to the average of the local spirals. Higher electron densities by up to a factor of three could, however, be possible for systematic uncertainties of the line flux estimates. The electron density of the QSO is comparable to high-$z$ star-forming galaxies at $z=1.5-2.3$, obtained using rest-frame optical lines and with the lower limits suggested from stacking analysis on lensed starbursts at $z=1-3.6$ using the same tracer of [NII]. Our results suggest a large scatter of electron densities in global scale at fixed star formation rates for extreme starbursts. The success of the [N II] 122$mu$m and 205$mu$m detections at $z=4.69$ demonstrates the power of future systematic surveys of extreme starbursts at $z>4$ for probing the ISM conditions and the effects on surrounding environments.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
