Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA SCUBA-2 Selected Herschel-SPIRE Dropout and the Nature of this Population
119
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Dusty star-forming galaxies (DSFGs) detected at $z > 4$ provide important examples of the first generations of massive galaxies. However, few examples with spectroscopic confirmation are currently known, with Hershel struggling to detect significant numbers of $z > 6$ DSFGs. NGP6_D1 is a bright 850 $mu m$ source (12.3 $pm$ 2.5 mJy) with no counterparts at shorter wavelengths (a SPIRE dropout). Interferometric observations confirm it is a single source, with no evidence for any optical or NIR emission, or nearby likely foreground lensing sources. No $>3sigma$ detected lines are seen in both LMT RSR and IRAM 30m EMIR spectra of NGP6_D1 across 32 $GHz$ of bandwidth despite reaching detection limits of $sim 1 mJy/500 km~s^{-1}$, so the redshift remains unknown. Template fitting suggests that NGP6_D1 is most likely between $z = 5.8$ and 8.3. SED analysis finds that NGP6_D1 is a ULIRG, with a dust mass $sim 10^8$ - $10^9$ $M_{odot}$ and a SFR of $sim$ 500 $M_{odot}~yr^{-1}$. We place upper limits on the gas mass of NGP6_D1 of $M_{H2}$ $ < (1.1~pm~3.5) times 10^{11}$ $M_{odot}$, consistent with a gas-to-dust ratio of $sim$ 100 - 1000. We discuss the nature of NGP6_D1 in the context of the broader submm population, and find that comparable SPIRE dropouts account for $sim$ 20% of all SCUBA-2 detected sources, but with a similar flux density distribution to the general population.
rate research
Read More
We present SCUBA-2 850-$mu$m observations of 13 candidate starbursting protoclusters selected using Planck and Herschel data. The cumulative number counts of the 850-$mu$m sources in 9/13 of these candidate protoclusters show significant overdensities compared to the field, with the probability $<$10$^{-2}$ assuming the sources are randomly distributed in the sky. Using the 250-, 350-, 500- and 850-$mu$m flux densities, we estimate the photometric redshifts of individual SCUBA-2 sources by fitting spectral energy distribution (SED) templates with an MCMC method. The photometric redshift distribution, peaking at $2<z<3$, is consistent with that of known $z>2$ protoclusters and the peak of the cosmic star-formation rate density (SFRD). We find that the 850-$mu$m sources in our candidate protoclusters have infrared luminosities of $L_{mathrm{IR}}gtrsim$10$^{12}L_{odot}$ and star-formation rates of SFR=(500-1,500)$M_{odot}$yr$^{-1}$. By comparing with results in the literature considering only Herschel photometry, we conclude that our 13 candidate protoclusters can be categorised into four groups: six of them being high-redshift starbursting protoclusters, one being a lower-redshift cluster/protocluster, three being protoclusters that contain lensed DSFG(s) or are rich in 850-$mu$m sources, and three regions without significant Herschel or SCUBA-2 source overdensities. The total SFRs of the candidate protoclusters are found to be comparable or higher than those of known protoclusters, suggesting our sample contains some of the most extreme protocluster population. We infer that cross-matching Planck and Herschel data is a robust method for selecting candidate protoclusters with overdensities of 850-$mu$m sources.
We present spectroscopic observations for a sample of 36 Herschel-SPIRE 250-500um selected galaxies (HSGs) at 2<z<5 from the Herschel Multi-tiered Extragalactic Survey (HerMES). Redshifts are confirmed as part of a large redshift survey of Herschel-SPIRE-selected sources covering ~0.93deg^2 in six extragalactic legacy fields. Observations were taken with the Keck I Low Resolution Imaging Spectrometer (LRIS) and the Keck II DEep Imaging Multi-Object Spectrograph (DEIMOS). Precise astrometry, needed for spectroscopic follow-up, is determined by identification of counterparts at 24um or 1.4GHz using a cross-identification likelihood matching method. Individual source luminosities range from log(L_IR/Lsun)=12.5-13.6 (corresponding to star formation rates 500-9000Msun/yr, assuming a Salpeter IMF), constituting some of the most intrinsically luminous, distant infrared galaxies yet discovered. We present both individual and composite rest-frame ultraviolet spectra and infrared spectral energy distributions (SEDs). The selection of these HSGs is reproducible and well characterized across large areas of sky in contrast to most z>2 HyLIRGs in the literature which are detected serendipitously or via tailored surveys searching only for high-z HyLIRGs; therefore, we can place lower limits on the contribution of HSGs to the cosmic star formation rate density at (7+-2)x10^(-3)Msun/yr h^3Mpc^(-3) at z~2.5, which is >10% of the estimated total star formation rate density (SFRD) of the Universe from optical surveys. The contribution at z~4 has a lower limit of 3x10^(-3)Msun/yr h^3 Mpc^(-3), ~>20% of the estimated total SFRD. This highlights the importance of extremely infrared-luminous galaxies with high star formation rates to the build-up of stellar mass, even at the earliest epochs.
We present SCUBA-2 follow-up of 61 candidate high-redshift Planck sources. Of these, 10 are confirmed strong gravitational lenses and comprise some of the brightest such submm sources on the observed sky, while 51 are candidate proto-cluster fields undergoing massive starburst events. With the accompanying Herschel-SPIRE observations and assuming an empirical dust temperature prior of $34^{+13}_{-9}$ K, we provide photometric redshift and far-IR luminosity estimates for 172 SCUBA-2-selected sources within these Planck overdensity fields. The redshift distribution of the sources peak between a redshift of 2 and 4, with one third of the sources having $S_{500}$/$S_{350} > 1$. For the majority of the sources, we find far-IR luminosities of approximately $10^{13},mathrm{L}_odot$, corresponding to star-formation rates of around $1000$ M$_odot mathrm{yr}^{-1}$. For $S_{850}>8$ mJy sources, we show that there is up to an order of magnitude increase in star-formation rate density and an increase in uncorrected number counts of $6$ for $S_{850}>8$ mJy when compared to typical cosmological survey fields. The sources detected with SCUBA-2 account for only approximately $5$ per cent of the Planck flux at 353 GHz, and thus many more fainter sources are expected in these fields.
High-redshift, luminous, dusty star forming galaxies (DSFGs) constrain the extremity of galaxy formation theories. The most extreme are discovered through follow-up on candidates in large area surveys. Here we present 850 $mu$m SCUBA-2 follow-up observations of 188 red DSFG candidates from the textit{Herschel} Multi-tiered Extragalactic Survey (HerMES) Large Mode Survey, covering 274 deg$^2$. We detected 87 per cent with a signal-to-noise ratio $>$ 3 at 850~$mu$m. We introduce a new method for incorporating the confusion noise in our spectral energy distribution fitting by sampling correlated flux density fluctuations from a confusion limited map. The new 850~$mu$m data provide a better constraint on the photometric redshifts of the candidates, with photometric redshift errors decreasing from $sigma_z/(1+z)approx0.21$ to $0.15$. Comparison spectroscopic redshifts also found little bias ($langle (z-z_{rm spec})/(1+z_{rm spec})rangle = 0.08 $). The mean photometric redshift is found to be 3.6 with a dispersion of $0.4$ and we identify 21 DSFGs with a high probability of lying at $z > 4$. After simulating our selection effects we find number counts are consistent with phenomenological galaxy evolution models. There is a statistically significant excess of WISE-1 and SDSS sources near our red galaxies, giving a strong indication that lensing may explain some of the apparently extreme objects. Nevertheless, our sample should include examples of galaxies with the highest star formation rates in the Universe ($gg10^3$ M$_odot$yr$^{-1}$).
We present Herschel observations from the Herschel Gould Belt Survey and SCUBA-2 science verification observations from the JCMT Gould Belt Survey of the B1 clump in the Perseus molecular cloud. We determined the dust emissivity index using four different techniques to combine the Herschel PACS+SPIRE data at 160 - 500 microns with the SCUBA-2 data at 450 microns and 850 microns. Of our four techniques, we found the most robust method was to filter-out the large-scale emission in the Herschel bands to match the spatial scales recovered by the SCUBA-2 reduction pipeline. Using this method, we find beta ~ 2 towards the filament region and moderately dense material and lower beta values (beta > 1.6) towards the dense protostellar cores, possibly due to dust grain growth. We find that beta and temperature are more robust with the inclusion of the SCUBA-2 data, improving estimates from Herschel data alone by factors of ~ 2 for beta and by ~ 40% for temperature. Furthermore, we find core mass differences of < 30% compared to Herschel-only estimates with an adopted beta = 2, highlighting the necessity of long wavelength submillimeter data for deriving accurate masses of prestellar and protostellar cores.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
