arXiv subjects

Michael Zemcov

Publications and source records attributed to Michael Zemcov.

72 records · Page 4Linked to original sources

arXiv2017

Low-Resolution Near-infrared Stellar Spectra Observed by the Cosmic Infrared Background Experiment (CIBER)

We present near-infrared (0.8-1.8 $μ$m) spectra of 105 bright (${m_{J}}$ $<$ 10) stars observed with the low resolution spectrometer on the rocket-borne Cosmic Infrared Background Experiment (CIBER). As our observations are performed above the earth's atmosphere, our spectra are free from telluric contamination, which makes them a unique resource for near-infrared spectral calibration. Two-Micron All Sky Survey (2MASS) photometry information is used to identify cross-matched stars after reduction and extraction of the spectra. We identify the spectral types of the observed stars by comparing them with spectral templates from the Infrared Telescope Facility (IRTF) library. All the observed spectra are consistent with late F to M stellar spectral types, and we identify various infrared absorption lines.

astro-ph.SR↗

arXiv2016

Intensity mapping of H-alpha, H-beta, [OII] and [OIII] lines at z<5

Intensity mapping is now becoming a useful tool to study the large-scale structure of the universe through spatial variations in the integrated emission from galaxies and the intergalactic medium. We study intensity mapping of the H-alpha 6563AA, [OIII]5007AA, [OII]3727AA and H-beta 4861AA lines at 0.8<z<5.2. The mean intensities of these four emission lines are estimated using the observed luminosity functions (LFs), cosmological simulations, and the star formation rate density (SFRD) derived from observations at z<5. We calculate the intensity power spectra and consider the foreground contamination of other lines at lower redshifts. We use the proposed NASA small explorer SPHEREx (the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer) as a case study for the detectability of the intensity power spectra of the four emission lines. We also investigate the cross correlation with the 21-cm line probed by CHIME (the Canadian Hydrogen Intensity Mapping Experiment), Tianlai experiment and SKA (the Square Kilometer Array) at 0.8<z<2.4. We find both the auto and cross power spectra can be well measured for the H-alpha, [OIII] and [OII] lines at z<3, while it is more challenging for the H-beta line. Finally, we estimate the constraint on the SFRD from intensity mapping, and find we can reach accuracy higher than 7% at z<4, which is better than usual measurements using the LFs of galaxies.

astro-ph.GA↗

arXiv2016

Science Impacts of the SPHEREx All-Sky Optical to Near-Infrared Spectral Survey: Report of a Community Workshop Examining Extragalactic, Galactic, Stellar and Planetary Science

SPHEREx is a proposed SMEX mission selected for Phase A. SPHEREx will carry out the first all-sky spectral survey and provide for every 6.2" pixel a spectra between 0.75 and 4.18 $μ$m [with R$\sim$41.4] and 4.18 and 5.00 $μ$m [with R$\sim$135]. The SPHEREx team has proposed three specific science investigations to be carried out with this unique data set: cosmic inflation, interstellar and circumstellar ices, and the extra-galactic background light. It is readily apparent, however, that many other questions in astrophysics and planetary sciences could be addressed with the SPHEREx data. The SPHEREx team convened a community workshop in February 2016, with the intent of enlisting the aid of a larger group of scientists in defining these questions. This paper summarizes the rich and varied menu of investigations that was laid out. It includes studies of the composition of main belt and Trojan/Greek asteroids; mapping the zodiacal light with unprecedented spatial and spectral resolution; identifying and studying very low-metallicity stars; improving stellar parameters in order to better characterize transiting exoplanets; studying aliphatic and aromatic carbon-bearing molecules in the interstellar medium; mapping star formation rates in nearby galaxies; determining the redshift of clusters of galaxies; identifying high redshift quasars over the full sky; and providing a NIR spectrum for most eROSITA X-ray sources. All of these investigations, and others not listed here, can be carried out with the nominal all-sky spectra to be produced by SPHEREx. In addition, the workshop defined enhanced data products and user tools which would facilitate some of these scientific studies. Finally, the workshop noted the high degrees of synergy between SPHEREx and a number of other current or forthcoming programs, including JWST, WFIRST, Euclid, GAIA, K2/Kepler, TESS, eROSITA and LSST.

astro-ph.CO↗

arXiv2016

An Algorithm for Real-Time Optimal Photocurrent Estimation including Transient Detection for Resource-Constrained Imaging Applications

Mega-pixel charge-integrating detectors are common in near-IR imaging applications. Optimal signal-to-noise ratio estimates of the photocurrents, which are particularly important in the low-signal regime, are produced by fitting linear models to sequential reads of the charge on the detector. Algorithms that solve this problem have a long history, but can be computationally intensive. Furthermore, the cosmic ray background is appreciable for these detectors in Earth orbit, particularly above the Earth's magnetic poles and the South Atlantic Anomaly, and on-board reduction routines must be capable of flagging affected pixels. In this paper we present an algorithm that generates optimal photocurrent estimates and flags random transient charge generation from cosmic rays, and is specifically designed to fit on a computationally restricted platform. We take as a case study the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx), a NASA Small Explorer astrophysics experiment concept, and show that the algorithm can easily fit in the resource-constrained environment of such a restricted platform. Detailed simulations of the input astrophysical signals and detector array performance are used to characterize the fitting routines in the presence of complex noise properties and charge transients. We use both Hubble Space Telescope Wide Field Camera-3 and Wide-field Infrared Survey Explorer to develop an empirical understanding of the susceptibility of near-IR detectors in low earth orbit and build a model for realistic cosmic ray energy spectra and rates. We show that our algorithm generates an unbiased estimate of the true photocurrent that is identical to that from a standard line fitting package, and characterize the rate, energy, and timing of both detected and undetected transient events.

astro-ph.IM↗

arXiv2016

Axion decay and anisotropy of near-IR extragalactic background light

The extragalactic background light (EBL) is comprised of the cumulative radiation from all galaxies and active galactic nuclei over the cosmic history. In addition to point sources, EBL also contains information from diffuse sources of radiation. The angular power spectra of the near-infrared intensities could contain additional signals and a complete understanding of the nature of the IR background is still lacking in the literature. Here we explore the constraints that can be placed on particle decays, especially candidate dark matter models involving axions that trace dark matter halos of galaxies. Axions with a mass around a few eV will decay via two photons with wavelengths in the near-IR band, and will leave a signature in the IR background intensity power spectrum. Using recent power spectra measurements from the Hubble Space Telescope (HST) and Cosmic Infrared Background Experiment (CIBER), we find that the 0.6 to 1.6 micron power spectra can be explained by axions with masses around 4 eV. The total axion abundance Omega_a~0.05, and it is comparable to the baryon density of the Universe. The suggested mean axion mass and abundance are not ruled out by existing cosmological observations. Interestingly, the axion model with a mass distribution is preferred by the data, which cannot be explained by the standard quantum chromodynamics (QCD) theory and needs further discussion.

astro-ph.CO↗

arXiv2016

Peculiar Velocity Constraints from Five-Band SZ Effect Measurements Towards RX J1347.5-1145 with MUSIC and Bolocam from the CSO

We present Sunyaev-Zel'dovich (SZ) effect measurements from wide-field images towards the galaxy cluster RX J1347.5-1145 obtained from the Caltech Submillimeter Observatory with the Multiwavelength Submillimeter Inductance Camera (MUSIC) at 147, 213, 281, and 337 GHz and with Bolocam at 140 GHz. As part of our analysis, we have used higher frequency data from Herschel-SPIRE and previously published lower frequency radio data to subtract the signal from the brightest dusty star-forming galaxies behind RX J1347.5-1145 and from the AGN in RX J1347.5-1145's BCG. Using these five-band SZ effect images, combined with X-ray spectroscopic measurements of the temperature of the intra-cluster medium (ICM) from Chandra, we constrain the ICM optical depth to be $τ_e = 7.33^{+0.96}_{-0.97} \times 10^{-3}$ and the ICM line of sight peculiar velocity to be $v_{pec} = -1040^{+870}_{-840}$ km s$^{-1}$. The errors for both quantities are limited by measurement noise rather than calibration uncertainties or astrophysical contamination, and significant improvements are possible with deeper observations. Our best-fit velocity is in good agreement with one previously published SZ effect analysis and in mild tension with the other, although some or all of that tension may be because that measurement samples a much smaller cluster volume. Furthermore, our best-fit optical depth implies a gas mass slightly larger than the Chandra-derived value, implying the cluster is elongated along the line of sight.

astro-ph.CO↗

arXiv2016

Cosmic Dawn Intensity Mapper

Cosmic Dawn Intensity Mapper is a "Probe Class" mission concept for reionization studies of the universe. It will be capable of spectroscopic imaging observations between 0.7 to 6-7 microns in the near-Infrared. The primary observational objective is pioneering observations of spectral emission lines of interest throughout the cosmic history, but especially from the first generation of distant, faint galaxies when the universe was less than 800 million years old. With spectro-imaging capabilities, using a set of linear variable filters (LVFs), CDIM will produce a three-dimensional tomographic view of the epoch of reionization (EoR). CDIM will also study galaxy formation over more than 90% of the cosmic history and will move the astronomical community from broad-band astronomical imaging to low-resolution (R=200-300) spectro-imaging of the universe.

astro-ph.CO↗

arXiv2015

Spatial and Temporal Stability of Airglow Measured in the Meinel Band Window at 1191.3 nm

We report on the temporal and spatial fluctuations in the atmospheric brightness in the narrow band between Meinel emission lines at 1191.3 nm using an R=320 near-infrared instrument. We present the instrument design and implementation, followed by a detailed analysis of data taken over the course of a night from Table Mountain Observatory. The absolute sky brightness at this wavelength is found to be 5330 +/- 30 nW m^-2 sr^-1, consistent with previous measurements of the inter-band airglow at these wavelengths. This amplitude is larger than simple models of the continuum component of the airglow emission at these wavelengths, confirming that an extra emissive or scattering component is required to explain the observations. We perform a detailed investigation of the noise properties of the data and find no evidence for a noise component associated with temporal instability in the inter-line continuum. This result demonstrates that in several hours of ~100s integrations the noise performance of the instrument does not appear to significantly degrade from expectations, giving a proof of concept that near-IR line intensity mapping may be feasible from ground-based sites.

astro-ph.IM↗

arXiv2014

On the Origin of Near-Infrared Extragalactic Background Light Anisotropy

Extragalactic background light (EBL) anisotropy traces variations in the total production of photons over cosmic history, and may contain faint, extended components missed in galaxy point source surveys. Infrared EBL fluctuations have been attributed to primordial galaxies and black holes at the epoch of reionization (EOR), or alternately, intra-halo light (IHL) from stars tidally stripped from their parent galaxies at low redshift. We report new EBL anisotropy measurements from a specialized sounding rocket experiment at 1.1 and 1.6 micrometers. The observed fluctuations exceed the amplitude from known galaxy populations, are inconsistent with EOR galaxies and black holes, and are largely explained by IHL emission. The measured fluctuations are associated with an EBL intensity that is comparable to the background from known galaxies measured through number counts, and therefore a substantial contribution to the energy contained in photons in the cosmos.

astro-ph.CO↗

arXiv2013

A Measurement of the Kinetic Sunyaev-Zel'dovich Signal Toward MACS J0717.5+3745

We report our analysis of MACS J0717.5+3745 using 140 and 268 GHz Bolocam data collected at the Caltech Submillimeter Observatory. We detect extended Sunyaev-Zel'dovich (SZ) effect signal at high significance in both Bolocam bands, and we employ Herschel-SPIRE observations to subtract the signal from dusty background galaxies in the 268 GHz data. We constrain the two-band SZ surface brightness toward two of the sub-clusters of MACS J0717.5+3745: the main sub-cluster (named C), and a sub-cluster identified in spectroscopic optical data to have a line-of-sight velocity of +3200 km/s (named B). We determine the surface brightness in two separate ways: via fits of parametric models and via direct integration of the images. For both sub-clusters, we find consistent surface brightnesses from both analysis methods. We constrain spectral templates consisting of relativistically corrected thermal and kinetic SZ signals, using a jointly-derived electron temperature from Chandra and XMM-Newton under the assumption that each sub-cluster is isothermal. The data show no evidence for a kinetic SZ signal toward sub-cluster C, but they do indicate a significant kinetic SZ signal toward sub-cluster B. The model-derived surface brightnesses for sub-cluster B yield a best-fit line-of-sight velocity of v_z = +3450 +- 900 km/s, with (1 - Prob[v_z > 0]) = 1.3 x 10^-5 (4.2 sigma away from 0 for a Gaussian distribution). The directly integrated sub-cluster B SZ surface brightnesses provide a best-fit v_z = +2550 +- 1050 km/s, with (1 - Prob[v_z > 0]) = 2.2 x 10^-3 (2.9 sigma).

astro-ph.CO↗

arXiv2012

A Population of Dust-Rich Quasars at z ~ 1.5

We report Herschel SPIRE (250, 350, and 500 micron) detections of 32 quasars with redshifts 0.5 < z < 3.6 from the Herschel Multi-tiered Extragalactic Survey. These sources are from a MIPS 24 micron flux-limited sample of 326 quasars in the Lockman Hole Field. The extensive multi-wavelength data available in the field permit construction of the rest-frame Spectral Energy Distributions (SEDs)from ultraviolet to the mid-infrared for all sources, and to the far-infrared (FIR) for the 32 objects. Most quasars with Herschel FIR detections show dust temperatures in the range of 25K to 60K, with a mean of 34K. The FIR luminosities range from 10^{11.3} to 10^{13.5} Lsun, qualifying most of their hosts as ultra- or hyper-luminous infrared galaxies. These FIR-detected quasars may represent a dust-rich population, but with lower redshifts and fainter luminosities than quasars observed at ~ 1 mm. However, their FIR properties cannot be predicted from shorter wavelengths (0.3--20 micron, rest-frame), and the bolometric luminosities derived using the 5100 A index may be underestimated for these FIR-detected quasars. Regardless of redshift, we observed a decline in the relative strength of FIR luminosities for quasars with higher near-infrared luminosities.

astro-ph.CO↗

arXiv2011

Intensity Mapping of the [CII] Fine Structure Line during the Epoch of Reionization

The atomic CII fine-structure line is one of the brightest lines in a typical star-forming galaxy spectrum with a luminosity ~ 0.1% to 1% of the bolometric luminosity. It is potentially a reliable tracer of the dense gas distribution at high redshifts and could provide an additional probe to the era of reionization. By taking into account of the spontaneous, stimulated and collisional emission of the CII line, we calculate the spin temperature and the mean intensity as a function of the redshift. When averaged over a cosmologically large volume, we find that the CII emission from ionized carbon in individual galaxies is larger than the signal generated by carbon in the intergalactic medium (IGM). Assuming that the CII luminosity is proportional to the carbon mass in dark matter halos, we also compute the power spectrum of the CII line intensity at various redshifts. In order to avoid the contamination from CO rotational lines at low redshift when targeting a CII survey at high redshifts, we propose the cross-correlation of CII and 21-cm line emission from high redshifts. To explore the detectability of the CII signal from reionization, we also evaluate the expected errors on the CII power spectrum and CII-21 cm cross power spectrum based on the design of the future milimeter surveys. We note that the CII-21 cm cross power spectrum contains interesting features that captures physics during reionization, including the ionized bubble sizes and the mean ionization fraction, which are challenging to measure from 21-cm data alone. We propose an instrumental concept for the reionization CII experiment targeting the frequency range of $\sim$ 200 to 300 GHz with 1, 3 and 10 meter apertures and a bolometric spectrometer array with 64 independent spectral pixels with about 20,000 bolometers.

astro-ph.CO↗

arXiv2011

Measuring Light from the Epoch of Reionization with CIBER, the Cosmic Infrared Background Experiment

Ultraviolet emission from the first generation of stars in the Universe ionized the intergalactic medium in a process which was completed by z~6; the wavelength of these photons has been redshifted by (1+z) into the near infrared today and can be measured using instruments situated above the Earth's atmosphere. First flying in February 2009, the Cosmic Infrared Background Experiment (CIBER) comprises four instruments housed in a single reusable sounding rocket borne payload. CIBER will measure spatial anisotropies in the extragalactic IR background caused by cosmological structure from the epoch of reionization using two broadband imaging instruments, make a detailed characterization of the spectral shape of the IR background using a low resolution spectrometer, and measure the absolute brightness of the Zodical light foreground with a high resolution spectrometer in each of our six science fields. This paper presents the scientific motivation for CIBER and details of its first two flights, including a review of the published scientific results from the first flight and an outlook for future reionization science with CIBER data.

astro-ph.CO↗

arXiv2010

The Herschel-SPIRE Legacy Survey (HSLS): the scientific goals of a shallow and wide submillimeter imaging survey with SPIRE

A large sub-mm survey with Herschel will enable many exciting science opportunities, especially in an era of wide-field optical and radio surveys and high resolution cosmic microwave background experiments. The Herschel-SPIRE Legacy Survey (HSLS), will lead to imaging data over 4000 sq. degrees at 250, 350, and 500 micron. Major Goals of HSLS are: (a) produce a catalog of 2.5 to 3 million galaxies down to 26, 27 and 33 mJy (50% completeness; 5 sigma confusion noise) at 250, 350 and 500 micron, respectively, in the southern hemisphere (3000 sq. degrees) and in an equatorial strip (1000 sq. degrees), areas which have extensive multi-wavelength coverage and are easily accessible from ALMA. Two thirds of the of the sources are expected to be at z > 1, one third at z > 2 and about a 1000 at z > 5. (b) Remove point source confusion in secondary anisotropy studies with Planck and ground-based CMB data. (c) Find at least 1200 strongly lensed bright sub-mm sources leading to a 2% test of general relativity. (d) Identify 200 proto-cluster regions at z of 2 and perform an unbiased study of the environmental dependence of star formation. (e) Perform an unbiased survey for star formation and dust at high Galactic latitude and make a census of debris disks and dust around AGB stars and white dwarfs.

astro-ph.CO↗

arXiv2009

Cosmic Infrared Background ExpeRiment (CIBER): A Probe of Extragalactic Background Light from Reionization

The Cosmic Infrared Background ExpeRiment (CIBER) is a rocket-borne absolute photometry imaging and spectroscopy experiment optimized to detect signatures of first-light galaxies present during reionization in the unresolved IR background. CIBER-I consists of a wide-field two-color camera for fluctuation measurements, a low-resolution absolute spectrometer for absolute EBL measurements, and a narrow-band imaging spectrometer to measure and correct scattered emission from the foreground zodiacal cloud. CIBER-I was successfully flown on February 25th, 2009 and has one more planned flight in early 2010. We propose, after several additional flights of CIBER-I, an improved CIBER-II camera consisting of a wide-field 30 cm imager operating in 4 bands between 0.5 and 2.1 microns. It is designed for a high significance detection of unresolved IR background fluctuations at the minimum level necessary for reionization. With a FOV 50 to 2000 times largerthan existing IR instruments on satellites, CIBER-II will carry out the definitive study to establish the surface density of sources responsible for reionization.

astro-ph.CO↗

arXiv2009

A New Era in Extragalactic Background Light Measurements: The Cosmic History of Accretion, Nucleosynthesis and Reionization

(Brief Summary) What is the total radiative content of the Universe since the epoch of recombination? The extragalactic background light (EBL) spectrum captures the redshifted energy released from the first stellar objects, protogalaxies, and galaxies throughout cosmic history. Yet, we have not determined the brightness of the extragalactic sky from UV/optical to far-infrared wavelengths with sufficient accuracy to establish the radiative content of the Universe to better than an order of magnitude. Among many science topics, an accurate measurement of the EBL spectrum from optical to far-IR wavelengths, will address: What is the total energy released by stellar nucleosynthesis over cosmic history? Was significant energy released by non-stellar processes? Is there a diffuse component to the EBL anywhere from optical to sub-millimeter? When did first stars appear and how luminous was the reionization epoch? Absolute optical to mid-IR EBL spectrum to an astrophysically interesting accuracy can be established by wide field imagingat a distance of 5 AU or above the ecliptic plane where the zodiacal foreground is reduced by more than two orders of magnitude.

astro-ph.CO↗

arXiv2003

Measurement of the Sunyaev-Zel'dovich Increment in Massive Galaxy Clusters

We have detected the Sunyaev-Zel'dovich (SZ) increment at 850 microns in two galaxy clusters (Cl 0016+16 and MS 1054.4-0321) using SCUBA (Sub-millimetre Common User Bolometer Array) on the James Clerk Maxwell Telescope. Fits to the isothermal βmodel yield a central Compton y parameter of (2.2 \pm 0.7) x 10^{-4} and a central 850 micron flux of ΔI_{0} = 2.2 \pm 0.7 mJy/beam in Cl 0016. This can be combined with decrement measurements to infer y = (2.38 \pm_{0.34}^{0.36}) x 10^{-4} and v_{pec} = 400 \pm_{1400}^{1900} km/s. In MS 1054 we find a peak 850 micron flux of ΔI_{0} = 2.0 \pm 1.0 mJy/beam and y = (2.0 \pm 1.0) x 10^{-4}. To be successful such measurements require large chop throws and non-standard data analysis techniques. In particular, the 450 micron data are used to remove atmospheric variations in the 850 micron data. An explicit annular model is fit to the SCUBA difference data in order to extract the radial profile, and separately fit to the model differences to minimize the effect of correlations induced by our scanning strategy. We have demonstrated that with sufficient care, SCUBA can be used to measure the SZ increment in massive, compact galaxy clusters.

astro-ph↗

arXiv2003

Estimates of Confusion and Gravitational Lensing Limits in Sunyaev-Zel'dovich Increment Measurements

We present estimates of the confusion limit of measurements of the Sunyaev-Zel'dovich effect (SZ) increment near its peak intensity based on Monte Carlo simulations of sub-millimetre observations of galaxy clusters. Specifically, we evaluate the contribution of gravitational lensing of high redshift background sources by a target cluster to its inferred SZ signal. We find that the background confusion limit is 0.6 mJy per beam without any lensing. With gravitational lensing, the confusion limit increases to 0.9 mJy per beam. Removing bright sources in the gravitationally lensed fields decreases the confusion limit to 0.7 mJy per beam, essentially background levels. These limits are found by removing exceptionally poor fits to the expected SZ profile, which are due to the different structure of the SZ and lensing angular profiles. We conclude that experiments designed to measure the SZ increment must have high enough angular resolution to identify background point sources while surveying enough of the sky to determine the SZ profile. Observations of the SZ increment with SCUBA, which has sufficient sensitivity and resolution for the task, should be straight forward.

astro-ph↗