SHARC-II 350 µm observations of the FF catalog are motivated based on as- trophysical as well as observational considerations. As discussed in § 1.1, studies of the IR/submm galaxy population over a wide redshift range is of great impor- tance for understanding the formation and evolution of this population. However, studies of dusty galaxies have so far been mostly focused on the low-redshift and high-redshift Universe, while flux measurements of dusty galaxies at intermediate redshifts remain relatively scarce. Situated in the redshift range of 0.1 < z < 1, observations of the FF sources nicely fill this void. IRAS observations provided us with valuable data points at 60 µm and 100 µm for the FF sources, but for this cata- log virtually no other FIR/submm continuum data points exist, particularly on the low frequency side of the rest-frame SED peak. Our 350 µm flux measurements are thus extremely valuable for attaining meaningful estimates of the SEDs. Precise measurements of spectroscopic redshifts allow accurate estimates of characteris- tic dust temperatures from the observed SEDs. Finally, targeted observations at 350 µm are made possible due to the positional accuracy provided by radio obser- vations. This is highly desirable for FIR/submm observations given the limited angular resolution currently available to telescopes working in this wavelength range.
Disentangling the complex spectro-morphological properties of high-redshift starburst galaxies is challeng- ing, given the capabilities of the current VLA (particu- larly, its lack of resolving power at low frequencies). How- ever these results (both the convex source-integrated ra- dio spectra and enlarged sizes at lower frequency relative to higher frequency) provide tantalising evidence that the processes of cosmic ray propagation – which domi- nate the spectral behaviour of, and create low-frequency radio continuum halos around nearby starburst galax- ies (e.g. Heesen et al. 2016; Mulcahy et al. 2018) – may also be at work (and be observable) in the environments of high-redshift starburst galaxies. Forthcoming instru- ments (such as SKA, and the proposed ngVLA) and deep imaging surveys being undertaken with existing longer- baseline interferometers (such as the e-MERLIN Galaxy Evolution survey, which maps the GOODS-N ﬁeld at 1.4 GHz at ∼ 0.3 ′′ resolution down to
Such resolved studies would help answer various open questions about SMGs. For example, by compiling a sample of z < 3.5 DSFGs that have rest-frame UV cov- erage, Casey et al. (2014b) have found significantly bluer UV continuum slopes (β) than the local star-forming galaxy (SFG) samples given a fixed IR-to-UV luminosity ratio (IRX). Casey et al. had argued that the geometrical effects in which a mismatch between the bulk of IR and UV emissions, which is also observed in the local ultra- luminous infrared galaxies (ULIRGs; Sanders & Mirabel 1996), could be one of the most important factors that causes the deviation of DSFGs from the nominal IRX-β relationship. By combining high resolution imaging of the optical and dust emission we can test these hypothe- ses.
AGN observed in Spitzer Space Telescope’s IRAC bands, and make deﬁnitive predictions for infrared X-ray correlations that should be testable by combining observations by Spitzer and the upcoming Herschel mission with X-ray surveys. To aid observational studies, we quantify the far-infrared X-ray correlations. Our dynamical approach allows us to directly correlate observed clustering in the data as seen in IRAC color-color plots with the relative amount of time the system spends in a region of color-color space. We also ﬁnd that this clustering is positively correlated with the stars dominating in their contribution to the total bolometric luminosity. The merger simulations also allow us to directly correlate the 850 µm ﬂux with the ratio of the black hole luminosity to the total luminosity, which is an inherent and testable feature of our model. We present photo albums spanning the lifetime of SMGs, from their infancy in the pre-merger phase to the ﬁnal stage as an elliptical galaxy, as seen in the observed 3.6 µm and 450 µm band to visually illustrate some of the morphological diﬀerences between mergers of diﬀering orbital inclination and progenitor redshift. We compare our SEDs from the simulations to observations of SMGs and ﬁnd good agreement. We ﬁnd that SMGs are a broader class of systems than starbursts or quasars. We introduce a simple, heuristic classiﬁcation scheme on the basis of the L IR /L x ratios of these galaxies, which may be interpreted qualitatively as an
Herschel has unprecedented spaUal resoluUon at far-‐infrared wavelengths and with the PACS and SPIRE instruments samples both sides of the peak in the far infrared spectral energy distribuUon. We can make maps of dust temperature, dust mass, emissivity index, gas-‐to-‐dust raUo and combine with a wealth of data at other wavelengths. These are produced by ﬁZng modiﬁed black bodies to the SED for each pixel.
annealing is a popular approach for many algorithmically insolvable problems and is, strictly speaking, a meta- heuristic solution (i.e. choices have to be made about the element to be optimised and also the method of optimis- ing). In simple terms the user must pick something to be minimised (or maximised), such as the total number of objects not assigned to a ﬁbre after tiling the whole sur- vey region. The user must also give the SANN algorithm variables to perturb (most obviously the right ascension and declination of the tile centres), and a rate at which it ‘cools’ towards a solution. Typically these perturbations become smaller as the solution improves, and eventually an acceptable set of tile positions should be found. Pack- ing problems lend themselves well to SANN since they can be tuned to ﬁnd acceptable solutions rapidly, but they are non-deterministic algorithms (unlike the other heuris- tic approaches discussed) and are neither provably optimal nor stable (i.e. small variations to the problem to be opti- mised can produce radically different results). In the case of the 6dFGS, SANN is obviously much more effective than any sort of regular tiling because the projected target densities vary signiﬁcantly and the survey area is large. The use of SANN reduces the number of sparsely popu- lated ﬁelds and better samples overdensities where ﬁelds would be full.
Our results and contamination estimates are limited by restrictions to galaxy-like sources and to Gaussian noise. The former is not likely to be an issue for space-based observations with high angular resolution, but it might affect ground-based surveys that do not have the ability to discriminate between compact galaxies and stars. The assumption of normally distributed errors is again likely to underestimate the occurrence of rare, extreme events of photometric scatter, since data are likely to have an excess of noise compared to a normal distribution in their tails ( Schmidt et al. 2014 ) . Thus, our results are to be considered lower limits for the contamination of dropout samples. Also, while we focused on Lyman-break selection, a similar analysis would be expected to hold qualitatively if we had considered photometric redshift estimates to construct the sample of dropouts and interlopers, with the added complication of leaving more degrees of freedom in de ﬁ ning the selection and the separation between the two samples.
However, selecting clusters based on their X-ray luminosities is likely to bias the high- redshift cluster samples towards the most massive and most virialized systems at that time. There are few such clusters in the local universe (due to the smaller volume probed), and so these clusters are likely not representative progenitors of local clusters. Hence, an increased effort has been made to select high-redshift clusters based on galaxy overdensities. One of the first such surveys conducted on a large scale was the Las Campanas Distant Cluster Survey (LCDCS, Gonzalez et al. 2001), which identified cluster candidates as peaks in the diffuse optical background light distribution. The ESO Distant Cluster Survey (EDisCS), which will be further discussed in the course of this thesis, is the follow-up survey of the most promising LCDCS cluster candidates. One of the first results from EDisCS was the observation of a deficit of faint red galaxies in high redshift clusters De Lucia et al. (2004b, 2007). Poggianti et al. (2006) studied the on-going star formation in EDisCS and SDSS galaxies and argued that the quiescent population is made up of two separate populations: “primordial” galaxies which ceased star formation long ago (z & 2.5) and galaxies whose star formation has been quenched upon entering the cluster environment, presumably on a long timescale ( ∼ 3 Gyr).
This method went out of fashion due to the unavailability of the galaxy grouping information that would accurately clas- sify the galaxies as centrals and satellites (Hoekstra 2014) as it was realised that these objects need to be modelled sepa- rately. Treating the galaxies as centrals and satellites in a sta- tistical way when considering the stacked signal could be natu- rally accounted for with the halo model (Seljak 2000; Peacock & Smith 2000; Cooray & Sheth 2002), thus overcoming the ob- servational shortcomings. In recent years the galaxy grouping information has become available due to the power of wide-field photometric surveys (e.g. KiDS; Kuijken et al. 2015; de Jong et al. 2015) complemented with spectroscopic group informa- tion (from spectroscopic surveys like GAMA; Driver et al. 2011; Robotham et al. 2011) that treat the central and satellite galaxies deterministically (e.g. Sifón et al. 2015; Brouwer et al. 2017). One important advantage of the two-dimensional method is that it exploits all the information of the actual image configuration (the model predicts the shear for each individual galaxy image) using various parameters, including the galaxies’ exact posi- tions, ellipticities, magnitudes, luminosities, stellar masses and group membership information rather than using only the en- semble properties of statistically equivalent samples (Schneider & Rix 1997). Moreover, the clustering of the lenses is naturally taken into account, although it is more difficult to account for the expected diversity in density profiles (Hoekstra 2014).
resolution of the far-IR/submm background through ground-based submm- and millimeter- wave surveys with SCUBA and MAMBO (e.g., Smail, Ivison, & Blain 1997; Hughes et al. 1998; Barger et al. 1998; Eales et al. 1999; Bertoldi et al. 2000) revealed a population of IR-luminous, but optically faint, high-redshift galaxies, whose submillimeter ﬂux densities suggest large bolometric luminosities ( ∼ 10 13 L ) mostly emitted in IR wavebands, when SEDs of local ULIRGs were used as templates. High rates of star formation (thousands of solar masses per year) and/or eﬃcient accretion of material onto an AGN are required to produce such luminosities. With a surface density on the sky of ∼ 0 . 2 arcmin − 2 for sources brighter than 4 mJy (Coppin et al. 2006), these galaxies are thought to contribute signiﬁcantly to the fraction of the luminosity density from high-redshift galaxies (Blain et al. 1999c). Understanding the nature of these luminous submm sources is important for determining the assembly of massive galaxies: if they are powered by star formation, then the huge star formation rates implied by their IR luminosities indicate a higher star formation rate density at high redshift than optically selected galaxies, which is diﬃcult to reconcile with CDM models of galaxy formation (Baugh et al. 2005), and suggest that massive galaxies formed the bulk of their stellar populations very quickly. On the other hand, if much of the luminosity of the submm sources is produced by accretion onto a central, supermassive black hole, then they represent important phases in supermassive black hole formation and the evolution of active galaxies. Even in the case that submm sources are AGN-dominated, they are still likely to be massive galaxies by extrapolating the local relation between the mass of central black holes and the bulge masses of their host galaxies to high redshifts.
The exceptional 3C 220.3 gravitational lensing system con- sists of an SMG (hosting a dust-enshrouded type-2 QSO) which is lensed by a PRG, i.e., a radio-loud type-2 quasar. The sys- tem permits determination of the total galaxy-scale mass for a powerful double-lobed radio galaxy that is not in a rich galaxy cluster. Comparison with available galaxy-scale lenses indicates an average to moderately high dark matter fraction, but the com- parison with radio-quiet galaxies needs to be confirmed with future lens samples near the redshift of 3C 220.3. Further ob- servations of 3C 220.3 with increased S/N will allow a more accurate lens model, give a better stellar mass measurement for the lenses, and allow a more detailed reconstruction of the SMG morphology. They should also clarify whether other galaxies important to the lensing, as for example in a small group, exist.
For these reasons, from a galaxy-formation perspective, large samples of massive galaxies with spectroscopic redshifts over a wide redshift range are highly desirable. Surveys such as zCOS- MOS (Lilly et al. 2007), VVDS (Le F`evre et al. 2004, 2015), DEEP2 (Newman et al. 2013), PRIMUS (Coil et al. 2011), and VIPERS (Guzzo et al. 2014) provide spectroscopic samples that probe the 0.2 < z < 1.0 universe and complement the Sloan Digital Sky Survey (SDSS; York et al. 2000) main sample at z = 0.1 (Strauss et al. 2002). These higher redshift surveys, however, still cover rela- tively small areas ranging from a few square degrees to a few tens of square degrees (e.g. VIPERS covers 24 deg 2 ). The volumes probed
MUSE observations of NGC 3311 were found to be publicly available on the ESO Science Archive Facility. The data were ob- tained between 2014–11–27 and 2015–01–21 as part of ESO Pro- gram 094.B-0711(A) (PI: Arnaboldi). The observations consist of a set of three pointings stretching north-east from the centre of NGC 3311 towards the halo, and a fourth pointing south-east of the centre of the galaxy, as shown in the left panel of Fig. 1. Exposure times ranged from 670 to 1370 seconds, with four exposures per pointing, and each pair of exposures has a position angle rotation of 90 degrees to reduce the appearance of the slicers and channels in the final combined datacube. Due to the large size of the galaxy and the small amount of uncontaminated sky background in each pointing, a separate sky exposure was observed alongside each set of science observations for sky subtraction. Additionally, a stan- dard star was observed on each night for flux calibration, sky flats were taken during twilight within 7 days, and internal lamp flats were taken with the calibration lamps at the start of each set of ob- servations to account for the time-dependent, temperature-related variations in the flux levels between each IFU. While such deep ob- servations of this galaxy are not strictly necessary for the analysis that we wish to undertake here, it will allow us to perform a more traditional study of the datacube for comparison which will pro- vide further confidence in applying this technique to lower-quality observations.
Observationally the regrowing of a disc in a post merger galaxy has been observed in the local Universe (see e.g. Hau et al. 2008; Kannappan et al. 2009; Salim et al. 2012; Moffett et al. 2012; Ueda et al. 2014; George 2017). Blue early type galaxies with signs of a disc seem to be primarily occur in low mass galaxies (e.g. < 3 × 10 10 M Kannappan et al. 2009). Compared to more massive galaxies, the regrowing of a disc after a major merger event in lower mass galaxies could be promoted by higher gas fractions (Catinella et al. 2010). The regrowing of a disc after a major merger event is hence theoretically possible and has been observed for a small sample of local galaxies. Yet the significance of this effect on the mass dependence of the merger quenching probability remains unclear. Robust to a mild mass dependence, the mass functions of galaxies along the merger quenching sequence would however only be affected if this is a strongly mass dependent effect. For instance, if 10 9 M galaxies are more than 50% more likely to regrow a disc than M ∗ galaxies, the resulting difference in the space densities at these masses would affect the α of the resulting mass func- tion. We make the simplified assumption that such an extreme effect is unlikely and neglect the process of disc reforming on the transition probability.
In a rich cluster of galaxies the gravitational field is strong enough to compress coronal gas to densities at which it can be readily detected either through its X-ray emission Gursky et al. (1971) or through distortion of the spectrum of the CMB via the SZ effect Sunyaev & Zeldovich (1972). In massive galaxy groups coronal gas can be detected through its X-ray emission, but in low-mass groups such as the Local Group the density and temperature of coronal gas is expected to be too low for detection in either X-rays or the SZ effect to be possible. However, we do have indirect indications of the existence of coronal gas within the Local Group. One indication is provided by ultraviolet observations of objects at high Galactic latitude, which reveal absorption by highly ionised species such as Ovi along lines of sight that pass close to Hi clouds Sembach et al. (2003); models of the interface between coronal gas and Hi predict the existence of regions rich in Ovi. In fact, long before the emergence of modern cosmology Spitzer (1956) inferred the existence of coronal gas from the existence of absorption lines of interstellar Na and Ca in the spectra of high-latitude stars by arguing that without a confining medium at ∼ T vir the clouds responsible for this absorption would quickly dissipate.
We have adjusted the zero-point of 0.21 mag in Zehavi et al. (2011) to 0.15 mag in order to better follow the ‘green valley’ and to get more equal-sized samples of blue and red galaxies. This colour cut works well at all redshifts (Fig. 6), although we see that the colour bimodality becomes far less obvious beyond redshift z = 0.2 due to the lack of low-luminosity, blue galaxies at these high redshifts. Although colour bimodality is more pronounced in (u − r) colour, e.g. Strateva et al. (2001), Baldry et al. (2004), u-band pho- tometry, even after forming a ‘pseudo-Petrosian’ magnitude (equa- tion 1) is rather noisy, and so we prefer to base our colour cuts on the more robust (g − r) colour. This colour cut (in the original form of Zehavi et al.) has also been used to investigate the angular clustering of galaxies by Christodoulou et al. (2011). One should also note that colour is not a proxy for galaxy morphology: many red galaxies are in fact dust-obscured disc galaxies (Driver et al. in prep.).
(1.5 mJy at 3.5σ ) of ALMA has enabled us to identify unambiguously the X-ray counterparts to the SMGs with high confidence for the first time among similar works. Due to a larger false-positive rate, source blending, and the poor positional precision in the previous generation submm surveys, earlier studies suffer from large uncertainty in their analyses. As an illustration of this issue, we compare with the submm sources and their X-ray counterparts identified in G11: among the 14 X-ray counterparts in G11, 7 are not recovered in our study, 22 and we find 3 more true X-ray counterparts that are not in G11 (ALESS 17.1, 70.1, and 73.1). We note these three additional matches are all submm bright (>4 mJy), and therefore this addition is not because our submm catalog (ALESS) is deeper than previous ones, which are typically at a limit of 3–4 mJy. ALESS 17.1 and 73.1 are discovered with X-ray counterparts due to the improvement of X-ray catalog depth (the 4 Ms Chandra catalog by X11 in this work, compared with the 2 Ms in Luo et al. 2008 used in G11). ALESS 70.1 is matched with an X-ray source due to its improved submm position. Such a large discrepancy in source matching could indicate that our agreement on the AGN fraction with G11 (and possibly also other similar studies) could be, at least partially, coincidental.
The sensor is also limited in mass and power budget by the small scale of the platform itself. We will, for instance, not be able to change the local oscillator to be sensitive to different ranges than those selected on the design board. A schematic sketch of the instrument can be seen in Fig. 1. The spec- trometer we plan to use is the chirp transform spectrometer designed for the Jupiter icy moon explorer’s submillimeter wave instrument, with 10 000 channels over a 1 GHz range (for examples on this type of spectrometer, see, e.g., Hartogh and Hartmann, 1990; Hartogh, 1997; Hartogh and Oster- schek, 1995; Villanueva and Hartogh, 2004; Villanueva et al., 2006; Paganini and Hartogh, 2009). The local oscillator will be at 481.15 GHz with a central intermediate frequency of 6 GHz. There will be no suppression of either of the side- bands, so the measured radiation will be between 474.65– 475.65 and 486.65–487.65 GHz. The system noise tempera- ture is expected to be about 2000 K in double-sideband mode. The antenna is planned to be 30 cm large and made of carbon fiber reinforced plastic. This achieves a 10 km vertical foot- print at orbit altitudes below about 400 km, with a resolution half-width of about 0.14 ◦ . A lower system noise would im- prove all results presented below, though the quoted number is as good as we expect the instrument will be at time of flight.
SIS receivers further is to use a dual-polarized receiver. When both polarizations are received simultaneously, there is a √ 2 improvement in signal to noise (S/N), or a factor of two reduction in observing time on a telescope for radio astronomy receivers. Also, one cannot improve the sensitivity by making lower-noise receivers if the sensitivity is already limited by atmospheric noise. This is now becoming the situation at the submillimeter wavelengths. The atmospheric transmission on a good night at the CSO is about 50% in the 600–700 GHz window, as can be seen from Figure 1.1, which contributes about 150 K of background noise. In this circumstances, to increase the sensitivity of ground-based radio astronomy receivers, one needs to build dual-polarized and/or side-band separation mixers. Dual polarization operation can be achieved either by quasi-optical means or by using waveguide components. At millimeter wavelengths, waveguide-based dual-polarized mixers are viable; however, at submillimeter wavelengths, quasi-optical designs are more practical.
This chapter will present a systematic study of the design, implementation, and performance analysis of an open-source readout (OSR) system for a superconducting microresonator array. The OSR system performs frequency-domain multiplexed real-time complex transmission measurements to monitor the instantaneous resonance frequency and dissipation of the KIDs. With a total of 16 readout units, our OSR system can read more than 3000 complex frequency channels simultaneously. All hardware, software, and firmware were successfully installed, tested, and optimized at the Caltech Submillimeter Observatory with the first MKID camera, MUSIC, in 2010 and 2012. The system demonstrated its ability to satisfy the requirements for detector readout, data acquisition, and telescope operation. As part of the MUSIC instrument, the OSR has been in use at the CSO for scientific observation since the summer of 2013.