| 1. |
- Jolly, Jean Baptiste, 1990, et al.
(författare)
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LINESTACKER: A spectral line stacking tool for interferometric data
- 2020
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 499:3, s. 3992-4010
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Tidskriftsartikel (refereegranskat)abstract
- LINESTACKER is a new open access and open source tool for stacking of spectral lines in interferometric data. LINESTACKER is an ensemble of CASA tasks, and can stack both 3D cubes or already extracted spectra. The algorithm is tested on increasingly complex simulated data sets, mimicking Atacama Large Millimeter/submillimeter Array, and Karl G. Jansky Very Large Array observations of [C II] and CO(3-2) emission lines, from z ∼ 7 and z ∼ 4 galaxies, respectively. We find that the algorithm is very robust, successfully retrieving the input parameters of the stacked lines in all cases with an accuracy ≳90 per cent. However, we distinguish some specific situations showcasing the intrinsic limitations of the method. Mainly that high uncertainties on the redshifts (∆z > 0.01) can lead to poor signal-to-noise ratio improvement, due to lines being stacked on shifted central frequencies. Additionally, we give an extensive description of the embedded statistical tools included in LINESTACKER: mainly bootstrapping, rebinning, and subsampling. Velocity rebinning is applied on the data before stacking and proves necessary when studying line profiles, in order to avoid artificial spectral features in the stack. Subsampling is useful to sort the stacked sources, allowing to find a subsample maximizing the searched parameters, while bootstrapping allows to detect inhomogeneities in the stacked sample. LINESTACKER is a useful tool for extracting the most from spectral observations of various types.
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| 2. |
- Stanley, Flora, 1990, et al.
(författare)
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A spectral stacking analysis to search for faint outflow signatures in z ∼6 quasars
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 631
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Tidskriftsartikel (refereegranskat)abstract
- Aims. Outflows in quasars during the early epochs of galaxy evolution are an important part of the feedback mechanisms that potentially affect the evolution of the host galaxy. However, systematic millimetre (mm) observations of outflows are only now becoming possible with the advent of sensitive mm telescopes. In this study we used spectral stacking methods to search for a faint high-velocity outflow signal in a sample of [C II] detected, z ∼ 6 quasars. Methods. We searched for broad emission line signatures from high-velocity outflows for a sample of 26 ∼ 6 quasars observed with the Atacama Large Millimeter Array (ALMA), with a detection of the [C II] line. The observed emission lines of the sources are dominated by the host galaxy, and outflow emission is not detected for the individual sources. We used a spectral line stacking analysis developed for interferometric data to search for outflow emission. We stacked both extracted spectra and the full spectral cubes. We also investigated the possibility that only a sub-set of our sample contributes to the stacked outflow emission. Results. We find only a tentative detection of a broad emission line component in the stacked spectra. When taking a region of about 2″ around the central position of the stacked cubes, the stacked line shows an excess emission due to a broad component of 1.1-1.5σ, but the significance drops to 0.4-0.7σ when stacking the extracted spectra from a smaller region. The broad component can be characterised by a line width of full width at half-maximum FWHM > 700 km s-1. Furthermore, we find a sub-sample of 12 sources, the stack of which maximises the broad component emission. The stack of this sub-sample shows an excess emission due to a broad component of 1.2-2.5σ. The stacked line of these sources has a broad component of FWHM > 775 km s-1. Conclusions. We find evidence suggesting the presence of outflows in a sub-sample of 12 out of 26 sources, which demonstrates the importance of spectral stacking techniques in tracing faint signal in galaxy samples. However, deeper ALMA observations are necessary to confirm the presence of a broad component in the individual spectra.
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| 3. |
- Cumming, Robert, 1967, et al.
(författare)
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Radioteleskop för alla
- 2021
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Ingår i: Fysikaktuellt. - 0283-9148. ; 2021:2, s. 5-7
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Vid Onsala rymdobservatorium finns två små radioteleskop som är tillgängliga för alla. SALSA-antennerna används flitigt av gymnasiestudenter från Sverige och hela världen. Ett nytt projekt på Chalmers ska göra det möjligt för fler och yngre studenter att själv styra ett eget teleskop, och få närkontakt med vår galax och annat i rymden.
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| 4. |
- Guerrero, Andrea, et al.
(författare)
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ALMA Lensing Cluster Survey: Average dust, gas, and star-formation properties of cluster and field galaxies from stacking analysis
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 526:2, s. 2423-2439
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Tidskriftsartikel (refereegranskat)abstract
- We develop new tools for continuum and spectral stacking of Atacama Large Millimeter/submillimeter Array (ALMA) data, and apply these to the ALMA Lensing Cluster Survey. We derive average dust masses, gas masses, and star-formation rates (SFRs) from the stacked observed 260-GHz continuum of 3402 individually undetected star-forming galaxies, of which 1450 are cluster galaxies and 1952 field galaxies, over three redshift and stellar mass bins (over z = 0-1.6 and log-11.7), and derive the average molecular gas content by stacking the emission line spectra in a SFR-selected subsample. The average SFRs and specific SFRs of both cluster and field galaxies are lower than those expected for main-sequence (MS) star-forming galaxies, and only galaxies with stellar mass of log-10.6 show dust and gas fractions comparable with those in the MS. The ALMA-Traced average 'highly obscured' SFRs are typically lower than the SFRs observed from optical to near-infrared spectral analysis. Cluster and field galaxies show similar trends in their contents of dust and gas, even when field galaxies were brighter in the stacked maps. From spectral stacking we find a potential CO (J = 4 → 3) line emission (signal-To-noise ratio being ∼4) when stacking cluster and field galaxies with the highest SFRs.
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| 5. |
- Jolly, Jean Baptiste, 1990
(författare)
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A study of galaxy evolution: stacking emission lines from distant galaxies
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To draw up a thorough description of galaxy evolution exhaustive observations are needed, of distant but mainly of faint galaxies. Describing low mass galaxies is important to move the focus from the tip of the iceberg. While advances in telescopes capabilities have allowed to reach further galaxy, high-redshift studies are especially biased toward the brightest galaxies. In addition, well resolved spectral observations are needed to fully characterise the studied galaxies. Permitting the detection of emission or absorption lines, giving a direct access to galaxy composition. But spectral observations imply reducing further the signal to noise ratio (SNR), making line observations in faint high-redshift galaxies a difficult task. Line stacking allows to get around intrinsic limitations in spectral observations, by averaging large galaxy samples, leading to drastic SNR improvement. However stacking, and especially line stacking, is not straightforward and requires a good handle of the population distribution, along with the output stack. To facilitate the use of such method, and to make data analysis tightly linked to stacking accessible, we produced an open source/open access tool, Line-Stacker. After introducing the current state of knowledge on galaxy evolution, I will present Line-Stacker, describing both its main algorithm as well as the embedded data analysis tools. I will then introduce the two included papers and present their results. Paper I consists in a thorough description of Line-Stacker, and its test on numerous different simulated data-sets. Paper II is the first application of Line-Stacker on real data, in which we studied outflows from z ∼ 6 quasars.
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| 6. |
- Jolly, Jean Baptiste, 1990, et al.
(författare)
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ALMA Lensing Cluster Survey: A spectral stacking analysis of [C II] in lensed z similar to 6 galaxies
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 652
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Tidskriftsartikel (refereegranskat)abstract
- Context. The properties of galaxies at redshift z>6 hold the key to our understanding of the early stages of galaxy evolution and can potentially identify the sources of the ultraviolet radiation that give rise to the epoch of reionisation. The far-infrared cooling line of [C II] at 158 mu m is known to be bright and correlate with the star formation rate (SFR) of low-redshift galaxies, and hence is also suggested to be an important tracer of star formation and interstellar medium properties for very high-redshift galaxies. Aims. With the aim to study the interstellar medium properties of gravitationally lensed galaxies at z>6, we search for [C II] and thermal dust emission in a sample of 52 > 6 galaxies observed by the ALMA Lensing Cluster Survey. Methods. We perform our analysis using LINESTACKER, stacking both [C II] and continuum emission. The target sample is selected from multiple catalogues, and the sample galaxies have spectroscopic redshift or low-uncertainty photometric redshifts (sigma(z)<0.02) in nine galaxy clusters. Source properties of the target galaxies are either extracted from the literature or computed using spectral energy distribution fitting. Both weighted-average and median stacking are used, on both the full sample and three sub-samples. Results. Our analyses find no detection of either [C II] or continuum. An upper limit on L-[CII] is derived, implying that [C II] remains marginally consistent for low-SFR z>6 galaxies but likely is under-luminous compared to the local L-[CII]-SFR relationship. We discuss potential biases and possible physical effects that may be the cause of the non-detection. Further, the upper limit on the dust continuum implies that less than half of the star formation is obscured.
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| 7. |
- Jolly, Jean Baptiste, 1990
(författare)
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Gas and dust in early galaxy evolution
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In order to study the content of distant galaxies without focusing solely on the brightest objects -- the tip of the iceberg -- I developed a tool: LineStacker. As its name indicates this tool was designed to perform spectral stacking analyses. Stacking allows to shed light on otherwise invisible features, by averaging together observations of many sources from a common galaxy population. Spectral lines emitted or absorbed by galaxies and the intergalactic medium carry information on the content of galaxies as well as their dynamics. The luminosity of certain atomic and molecular spectral lines is known to correlate with fundamental physical properties of galaxies, such as star formation rate. In addition, the shape of the lines can trace global dynamics of galaxies or peculiar events such as outflows. In this context, I used LineStacker to study distant galaxies by observing the average spectral lines, or continuum emission, emitted by a particular galaxy population. In this thesis I present the tool LineStacker in detail and with a specific emphasis on the statistical tools included with it. In addition, I showcase three different analyses where we used LineStacker to study galaxy evolution. In the two first we studied ionized carbon, [CII], in galaxies at redshift z∼6. One project focused on the faint outflow signatures below the main [CII] line, while the other project focused on the overall [CII] emission from faint, gravitationally lensed galaxies. Finally, in the last analysis, we studied the overall dust mass as well as the comoving dust mass density and their evolution with redshift. The results from all the analyses highlight the power and efficiency of stacking as a method, and the necessity to go beyond studying the brightest objects.
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| 8. |
- Kokorev, V., et al.
(författare)
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ALMA Lensing Cluster Survey: Hubble Space Telescope and Spitzer Photometry of 33 Lensed Fields Built with CHArGE
- 2022
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Ingår i: Astrophysical Journal, Supplement Series. - : American Astronomical Society. - 1538-4365 .- 0067-0049. ; 263:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a set of multiwavelength mosaics and photometric catalogs in the Atacama Large Millimeter/ submillimeter Array (ALMA) lensing cluster survey fields. The catalogs were built by the reprocessing of archival data from the Complete Hubble Archive for Galaxy Evolution compilation, taken by the Hubble Space Telescope (HST) in the Reionization Lensing Cluster Survey, Cluster Lensing And Supernova survey with Hubble, and Hubble Frontier Fields. Additionally, we have reconstructed the Spitzer Infrared Array Camera 3.6 and 4.5 μm mosaics, by utilizing all the available archival IPAC Infrared Science Archive/Spitzer Heritage Archive exposures. To alleviate the effect of blending in such a crowded region, we have modeled the Spitzer photometry by convolving the HST detection image with the Spitzer point-spread function using the novel GOLFIR software. The final catalogs contain 218,000 sources, covering a combined area of 690 arcmin2, a factor of ∼2 improvement over the currently existing photometry. A large number of detected sources is a result of reprocessing of all available and sometimes deeper exposures, in conjunction with a combined optical–near-IR detection strategy. These data will serve as an important tool in aiding the search of the submillimeter galaxies in future ALMA surveys, as well as follow-ups of the HST dark and high-z sources with JWST. Coupled with the available HST photometry, the addition of the 3.6 and 4.5 μm bands will allow us to place a better constraint on the photometric redshifts and stellar masses of these objects, thus giving us an opportunity to identify high-redshift candidates for spectroscopic follow-ups and to answer the important questions regarding the Epoch of Reionization and formation of the first galaxies. The mosaics, photometric catalogs, and the best-fit physical properties are publicly available at https:// github.com/dawn-cph/alcs-clusters.
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| 9. |
- Sun, Fengwu, et al.
(författare)
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Extensive Lensing Survey of Optical and Near-infrared Dark Objects (El Sonido): HST H-faint Galaxies behind 101 Lensing Clusters
- 2021
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 922:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a Spitzer/IRAC survey of H-faint (H-160 greater than or similar to 26.4, < 5 sigma) sources in 101 lensing cluster fields. Across a CANDELS/Wide-like survey area of similar to 648 arcmin(2) (effectively similar to 221 arcmin(2) in the source plane), we have securely discovered 53 sources in the IRAC Channel-2 band (CH2, 4.5 mu m; median CH2 = 22.46 +/- 0.11 AB mag) that lack robust HST/WFC3-IR F160W counterparts. The most remarkable source in our sample, namely ES-009 in the field of Abell 2813, is the brightest H-faint galaxy at 4.5 mu m known so far (CH2 = 20.48 +/- 0.03 AB mag). We show that the H-faint sources in our sample are massive (median M-star = 10 10.3 +/- 0.3 M-circle dot, star-forming (median star formation rate =1001 M-circle dot yr(-1)), and dust-obscured (A(v) = 2.6 +/- 0.3) galaxies around a median photometric redshift of z = 3.9 +/- 0.4. The stellar continua of 14 H-faint galaxies can be resolved in the CH2 band, suggesting a median circularized effective radius (R-e,R-circ; lensing corrected) of 1.9 +/- 0.2 kpc and <1.5 kpc for the resolved and whole samples, respectively. This is consistent with the sizes of massive unobscured galaxies at z similar to 4, indicating that H-faint galaxies represent the dusty tail of the distribution of a wider galaxy population. Comparing with the ALMA dust continuum sizes of similar galaxies reported previously, we conclude that the heavy dust obscuration in H-faint galaxies is related to the compactness of both stellar and dust continua (R-e,R-circ similar to 1 kpc). These H-faint galaxies make up 161 3 % of the galaxies in the stellar-mass range of 10(10) - 10(11.2) M-circle dot at z = 3 similar to 5, contributing to 8(-4)(+8)% of the cosmic star formation rate density in this epoch and likely tracing the early phase of massive galaxy formation.
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