Engineering topics

Charmandaris, Vassilis

Publications and source records attributed to Charmandaris, Vassilis.

15 records

DOE OSTI2024

Terrestrial Very-Long-Baseline Atom Interferometry: Workshop Summary

This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI proto-collaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial large-scale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more km-scale detectors, which will be operational in the mid-2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space

We propose in this White Paper a concept for a space experiment using cold atoms to search for ultra-light dark matter, and to detect gravitational waves in the frequency range between the most sensitive ranges of LISA and the terrestrial LIGO/Virgo/KAGRA/INDIGO experiments. This interdisciplinary experiment, called Atomic Experiment for Dark Matter and Gravity Exploration (AEDGE), will also complement other planned searches for dark matter, and exploit synergies with other gravitational wave detectors. We give examples of the extended range of sensitivity to ultra-light dark matter offered by AEDGE, and how its gravitational-wave measurements could explore the assembly of super-massive black holes, first-order phase transitions in the early universe and cosmic strings. AEDGE will be based upon technologies now being developed for terrestrial experiments using cold atoms, and will benefit from the space experience obtained with, e.g., LISA and cold atom experiments in microgravity. This paper is based on a submission (v1) in response to the Call for White Papers for the Voyage 2050 long-term plan in the ESA Science Programme. ESA limited the number of White Paper authors to 30. However, in this version (v2) we have welcomed as supporting authors participants in the Workshop on Atomic Experiments for Dark Matter and Gravity Exploration held at CERN: ({\tt https://indico.cern.ch/event/830432/}), as well as other interested scientists, and have incorporated additional material.

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DOE OSTI2017

ALMA Maps of Dust and Warm Dense Gas Emission in the Starburst Galaxy IC 5179

We present our high-resolution (0.″15 × 0.″13, ∼34 pc) observations of the CO (6−5) line emission, which probes the warm and dense molecular gas, and the 434 μ m dust continuum emission in the nuclear region of the starburst galaxy IC 5179, conducted with the Atacama Large Millimeter Array (ALMA). The CO (6−5) emission is spatially distributed in filamentary structures with many dense cores and shows a velocity field that is characteristic of a circumnuclear rotating gas disk, with 90% of the rotation speed arising within a radius of ≲150 pc. At the scale of our spatial resolution, the CO (6−5) and dust emission peaks do not always coincide, with their surface brightness ratio varying by a factor of ∼10. This result suggests that their excitation mechanisms are likely different, as further evidenced by the southwest to northeast spatial gradient of both CO-to-dust continuum ratio and Pa- α equivalent width. Within the nuclear region (radius ∼ 300 pc) and with a resolution of ∼34 pc, the CO line flux (dust flux density) detected in our ALMA observations is 180 ± 18 Jy km s{sup −1} (71 ± 7 mJy), which accounts for 22% (2.4%) of the total value measured by Herschel .

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DOE OSTI2017

ALMA [N ii] 205 μ m Imaging Spectroscopy of the Interacting Galaxy System BRI 1202-0725 at Redshift 4.7

We present the results from Atacama Large Millimeter/submillimeter Array imaging in the [N ii] 205 μ m fine-structure line (hereafter [N ii]) and the underlying continuum of BRI 1202-0725, an interacting galaxy system at z = 4.7, consisting of a quasi-stellar object (QSO), a submillimeter galaxy (SMG), and two Ly α emitters, all within ∼25 kpc of the QSO. We detect the QSO and SMG in both [N ii] and continuum. At the ∼1″ (or 6.6 kpc) resolution, both the QSO and SMG are resolved in [N ii], with the de-convolved major axes of ∼9 and ∼14 kpc, respectively. In contrast, their continuum emissions are much more compact and unresolved even at an enhanced resolution of ∼0.″7. The ratio of the [N ii] flux to the existing CO(7−6) flux is used to constrain the dust temperature ( T {sub dust}) for a more accurate determination of the FIR luminosity L {sub FIR}. Our best estimated T {sub dust} equals 43 (±2) K for both galaxies (assuming an emissivity index β = 1.8). The resulting L {sub CO(7−6)}/ L {sub FIR} ratios are statistically consistent with that of local luminous infrared galaxies, confirming that L {sub CO(7−6)} traces the star formation (SF) rate (SFR) in these galaxies. We estimate that the ongoing SF of the QSO (SMG) has an SFR of 5.1 (6.9) × 10{sup 3} M {sub ⊙} yr{sup −1} (±30%) assuming Chabrier initial mass function, takes place within a diameter (at half maximum) of 1.3 (1.5) kpc, and will consume the existing 5 (5) × 10{sup 11} M {sub ⊙} of molecular gas in 10 (7) × 10{sup 7} years.

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DOE OSTI2017

A Herschel Space Observatory Spectral Line Survey of Local Luminous Infrared Galaxies from 194 to 671 Microns

We describe a Herschel Space Observatory 194–671 μm spectroscopic survey of a sample of 121 local luminous infrared galaxies and report the fluxes of the CO J to J–1 rotational transitions for 4⩽J⩽13, the [N ii] 205 μm line, the [C i] lines at 609 and 370 μm, as well as additional and usually fainter lines. The CO spectral line energy distributions (SLEDs) presented here are consistent with our earlier work, which was based on a smaller sample, that calls for two distinct molecular gas components in general: (i) a cold component, which emits CO lines primarily at J ≲ 4 and likely represents the same gas phase traced by CO (1−0), and (ii) a warm component, which dominates over the mid-J regime (4 < J ≲ 10) and is intimately related to current star formation. We present evidence that the CO line emission associated with an active galactic nucleus is significant only at J > 10. The flux ratios of the two [C i] lines imply modest excitation temperatures of 15–30 K; the [C i] 370 μm line scales more linearly in flux with CO (4−3) than with CO (7−6). These findings suggest that the [C i] emission is predominantly associated with the gas component defined in (i) above. Our analysis of the stacked spectra in different far-infrared (FIR) color bins reveals an evolution of the SLED of the rotational transitions of H{sub 2}O vapor as a function of the FIR color in a direction consistent with infrared photon pumping.

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DOE OSTI2016

ALMA IMAGING OF THE CO (6-5) LINE EMISSION IN NGC 7130

In this paper, we report our high-resolution (0.″20 × 0.″14 or ∼70 × 49 pc) observations of the CO(6-5) line emission, which probes warm and dense molecular gas, and the 434 μm dust continuum in the nuclear region of NGC 7130, obtained with the Atacama Large Millimeter Array (ALMA). The CO line and dust continuum fluxes detected in our ALMA observations are 1230 ± 74 Jy km s{sup −1} and 814 ± 52 mJy, respectively, which account for 100% and 51% of their total fluxes. We find that the CO(6-5) and dust emissions are generally spatially correlated, but their brightest peaks show an offset of ∼70 pc, suggesting that the gas and dust emissions may start decoupling at this physical scale. The brightest peak of the CO(6-5) emission does not spatially correspond to the radio continuum peak, which is likely dominated by an active galactic nucleus (AGN). This, together with our additional quantitative analysis, suggests that the heating contribution of the AGN to the CO(6-5) emission in NGC 7130 is negligible. The CO(6-5) and the extinction-corrected Pa-α maps display striking differences, suggestive of either a breakdown of the correlation between warm dense gas and star formation at linear scales of <100 pc or a large uncertainty in our extinction correction to the observed Pa-α image. Over a larger scale of ∼2.1 kpc, the double-lobed structure found in the CO(6-5) emission agrees well with the dust lanes in the optical/near-infrared images.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2016

The [N ii] 205 μm emission in local luminous infrared galaxies

In this paper, we present the measurements of the [N ii] 205 μm line for a flux-limited sample of 122 (ultra-)luminous infrared galaxies [(U)LIRGs] and 20 additional normal galaxies, obtained with the Herschel Space Observatory (Herschel). We explore the far-infrared (FIR) color dependence of the [N ii] 205 μm (L{sub [N ii]205 μm}) to the total infrared (L{sub IR}) luminosity ratio, and find that L{sub [N ii]205 μm}/L{sub IR} only depends modestly on the 70–160 μm flux density ratio (f{sub 70}/f{sub 160}) when f{sub 70}/f{sub 160}≲0.6, whereas such dependence becomes much steeper for f{sub 70}/f{sub 160}>0.6. We also investigate the relation between L{sub [N ii]205 μm} and star formation rate (SFR), and show that L{sub [N ii]205 μm} has a nearly linear correlation with SFR, albeit the intercept of such a relation varies somewhat with f{sub 60}/f{sub 100}, consistent with our previous conclusion that [N ii] 205 μm emission can serve as an SFR indicator with an accuracy of ∼0.4 dex, or ∼0.2 dex if f{sub 60}/f{sub 100} is known independently. Furthermore, together with the Infrared Space Observatory measurements of [N ii], we use a total of ∼200 galaxies to derive the local [N ii] 205 μm luminosity function (LF) by tying it to the known IR LF with a bivariate method. As a practical application, we also compute the local SFR volume density ( ρ-dot {sub SFR}) using the newly derived SFR calibrator and LF. The resulting log ρ-dot {sub SFR}=−1.96±0.11 M{sub ⊙} yr{sup −1} Mpc{sup −3} agrees well with previous studies. Finally, we determine the electron densities (n{sub e}) of the ionized medium for a subsample of 12 (U)LIRGs with both [N ii] 205 μm and [N ii] 122 μm data, and find that n{sub e} is in the range of ∼1–100 cm{sup −3}, with a median value of 22 cm{sup −3}.

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DOE OSTI2015

MEASURING STAR FORMATION RATES AND FAR-INFRARED COLORS OF HIGH-REDSHIFT GALAXIES USING THE CO(7–6) AND [N II] 205 μm LINES

To better characterize the global star formation activity in a galaxy, one needs to know not only the star formation rate (SFR) but also the rest-frame, far-infrared color (e.g., the 60–100 μm color, C(60/100)) of the dust emission. The latter probes the average intensity of the dust heating radiation field and scales statistically with the effective SFR surface density in star-forming galaxies including (ultra-)luminous infrared galaxies ((U)LIRGs). To this end, here we exploit a new spectroscopic approach involving only two emission lines: CO(7–6) at 372 μm and [N ii] at 205 μm([N ii]{sub 205μm}). For local (U)LIRGs, the ratios of the CO(7–6) luminosity (L{sub CO(7–6)}) to the total infrared luminosity (L{sub IR}; 8–1000 μm) are fairly tightly distributed (to within ∼0.12 dex) and show little dependence on C(60/100). This makes L{sub CO(7–6)} a good SFR tracer, which is less contaminated by active galactic nuclei than L{sub IR} and may also be much less sensitive to metallicity than L{sub CO(1–0)}. Furthermore, the logarithmic [N ii]{sub 205μm}/CO(7–6) luminosity ratio depends fairly strongly (at a slope of ∼ −1.4) on C(60/100), with a modest scatter (∼0.23 dex). This makes it a useful estimator on C(60/100) with an implied uncertainty of ∼0.15 (or ≲4 K in the dust temperature (T{sub dust}) in the case of a graybody emission with T{sub dust} ≳ 30 K and a dust emissivity index β ≥ 1). Our locally calibrated SFR and C(60/100) estimators are shown to be consistent with the published data of (U)LIRGs of z up to ∼6.5.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2013

GOODS-HERSCHEL: SEPARATING HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI AND STAR-FORMING GALAXIES USING INFRARED COLOR DIAGNOSTICS

We have compiled a large sample of 151 high-redshift (z = 0.5-4) galaxies selected at 24 {mu}m (S {sub 24} > 100 {mu}Jy) in the GOODS-N and ECDFS fields for which we have deep Spitzer IRS spectroscopy, allowing us to decompose the mid-infrared spectrum into contributions from star formation and activity in the galactic nuclei. In addition, we have a wealth of photometric data from Spitzer IRAC/MIPS and Herschel PACS/SPIRE. We explore how effective different infrared color combinations are at separating our mid-IR spectroscopically determined active galactic nuclei from our star-forming galaxies. We look in depth at existing IRAC color diagnostics, and we explore new color-color diagnostics combining mid-IR, far-IR, and near-IR photometry, since these combinations provide the most detail about the shape of a source's IR spectrum. An added benefit of using a color that combines far-IR and mid-IR photometry is that it is indicative of the power source driving the IR luminosity. For our data set, the optimal color selections are S {sub 250}/S {sub 24} versus S {sub 8}/S {sub 3.6} and S {sub 100}/S {sub 24} versus S {sub 8}/S {sub 3.6}; both diagnostics have {approx}10% contamination rate in the regions occupied primarily by star-forming galaxies and active galactic nuclei, respectively. Based on the low contamination rate, these two new IR color-color diagnostics are ideal for estimating both the mid-IR power source of a galaxy when spectroscopy is unavailable and the dominant power source contributing to the IR luminosity. In the absence of far-IR data, we present color diagnostics using the Wide-field Infrared Survey Explorer mid-IR bands which can efficiently select out high-z (z {approx} 2) star-forming galaxies.

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DOE OSTI2012

GOODS-HERSCHEL: IMPACT OF ACTIVE GALACTIC NUCLEI AND STAR FORMATION ACTIVITY ON INFRARED SPECTRAL ENERGY DISTRIBUTIONS AT HIGH REDSHIFT

We explore the effects of active galactic nuclei (AGNs) and star formation activity on the infrared (0.3-1000 {mu}m) spectral energy distributions (SEDs) of luminous infrared galaxies from z = 0.5 to 4.0. We have compiled a large sample of 151 galaxies selected at 24 {mu}m (S {sub 24} {approx}> 100 {mu}Jy) in the GOODS-N and ECDFS fields for which we have deep Spitzer IRS spectroscopy, allowing us to decompose the mid-IR spectrum into contributions from star formation and AGN activity. A significant portion ({approx}25%) of our sample is dominated by an AGN (>50% of the mid-IR luminosity) in the mid-IR. Based on the mid-IR classification, we divide our full sample into four sub-samples: z {approx} 1 star-forming (SF) sources, z {approx} 2 SF sources, AGNs with clear 9.7 {mu}m silicate absorption, and AGNs with featureless mid-IR spectra. From our large spectroscopic sample and wealth of multi-wavelength data, including deep Herschel imaging at 100, 160, 250, 350, and 500 {mu}m, we use 95 galaxies with complete spectral coverage to create a composite SED for each sub-sample. We then fit a two-temperature component modified blackbody to the SEDs. We find that the IR SEDs have similar cold dust temperatures, regardless of the mid-IR power source, but display a marked difference in the warmer dust temperatures. We calculate the average effective temperature of the dust in each sub-sample and find a significant ({approx}20 K) difference between the SF and AGN systems. We compare our composite SEDs to local templates and find that local templates do not accurately reproduce the mid-IR features and dust temperatures of our high-redshift systems. High-redshift IR luminous galaxies contain significantly more cool dust than their local counterparts. We find that a full suite of photometry spanning the IR peak is necessary to accurately account for the dominant dust temperature components in high-redshift IR luminous galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

EVIDENCE FOR A WIDE RANGE OF ULTRAVIOLET OBSCURATION IN z {approx} 2 DUSTY GALAXIES FROM THE GOODS-HERSCHEL SURVEY

Dusty galaxies at z {approx} 2 span a wide range of relative brightness between rest-frame mid-infrared (8 {mu}m) and ultraviolet wavelengths. We attempt to determine the physical mechanism responsible for this diversity. Dust-obscured galaxies (DOGs), which have rest-frame mid-IR to UV flux density ratios {approx}> 1000, might be abnormally bright in the mid-IR, perhaps due to prominent emission from active galactic nuclei and/or polycyclic aromatic hydrocarbons, or abnormally faint in the UV. We use far-infrared data from the GOODS-Herschel survey to show that most DOGs with 10{sup 12} L {sub Sun} {approx}< L {sub IR} {approx}< 10{sup 13} L {sub Sun} are not abnormally bright in the mid-IR when compared to other dusty galaxies with similar IR (8-1000 {mu}m) luminosities. We observe a relation between the median IR to UV luminosity ratios and the median UV continuum power-law indices for these galaxies, and we find that only 24% have specific star formation rates that indicate the dominance of compact star-forming regions. This circumstantial evidence supports the idea that the UV- and IR-emitting regions in these galaxies are spatially coincident, which implies a connection between the abnormal UV faintness of DOGs and dust obscuration. We conclude that the range in rest-frame mid-IR to UV flux density ratios spanned by dusty galaxies at z {approx} 2 is due to differing amounts of UV obscuration. Of galaxies with these IR luminosities, DOGs are the most obscured. We attribute differences in UV obscuration to either (1) differences in the degree of alignment between the spatial distributions of dust and massive stars or (2) differences in the total dust content.

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DOE OSTI2012

A UNIFIED EMPIRICAL MODEL FOR INFRARED GALAXY COUNTS BASED ON THE OBSERVED PHYSICAL EVOLUTION OF DISTANT GALAXIES

We reproduce the mid-infrared to radio galaxy counts with a new empirical model based on our current understanding of the evolution of main-sequence (MS) and starburst (SB) galaxies. We rely on a simple spectral energy distribution (SED) library based on Herschel observations: a single SED for the MS and another one for SB, getting warmer with redshift. Our model is able to reproduce recent measurements of galaxy counts performed with Herschel, including counts per redshift slice. This agreement demonstrates the power of our 2-Star-Formation Modes (2SFM) decomposition in describing the statistical properties of infrared sources and their evolution with cosmic time. We discuss the relative contribution of MS and SB galaxies to the number counts at various wavelengths and flux densities. We also show that MS galaxies are responsible for a bump in the 1.4 GHz radio counts around 50 {mu}Jy. Material of the model (predictions, SED library, mock catalogs, etc.) is available online.

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DOE OSTI2012

GOODS-HERSCHEL AND CANDELS: THE MORPHOLOGIES OF ULTRALUMINOUS INFRARED GALAXIES AT z {approx} 2

Using deep 100 and 160 {mu}m observations in GOODS-South from GOODS-Herschel, combined with high-resolution HST/WFC3 near-infrared imaging from CANDELS, we present the first detailed morphological analysis of a complete, far-infrared (FIR) selected sample of 52 ultraluminous infrared galaxies (ULIRGs; L{sub IR} > 10{sup 12} L{sub Sun }) at z {approx} 2. We also make use of a comparison sample of galaxies with lower IR luminosities but with the same redshift and H-band magnitude distribution. Our visual classifications of these two samples indicate that the fractions of objects with disk and spheroid morphologies are roughly the same but that there are significantly more mergers, interactions, and irregular galaxies among the ULIRGs (72{sup +5}{sub -7}% versus 32 {+-} 3%). The combination of disk and irregular/interacting morphologies suggests that early-stage interactions, minor mergers, and disk instabilities could play an important role in ULIRGs at z {approx} 2. We compare these fractions with those of a z {approx} 1 sample selected from GOODS-H and COSMOS across a wide luminosity range and find that the fraction of disks decreases systematically with L{sub IR} while the fraction of mergers and interactions increases, as has been observed locally. At comparable luminosities, the fraction of ULIRGs with various morphological classifications is similar at z {approx} 2 and z {approx} 1, though there are slightly fewer mergers and slightly more disks at higher redshift. We investigate the position of the z {approx} 2 ULIRGs, along with 70 z {approx} 2 LIRGs, on the specific star formation rate versus redshift plane, and find 52 systems to be starbursts (i.e., they lie more than a factor of three above the main-sequence relation). We find that many of these systems are clear interactions and mergers ({approx}50%) compared to only 24% of systems on the main sequence relation. If irregular disks are included as potential minor mergers, then we find that up to {approx}73% of starbursts are involved in a merger or interaction at some level. Although the final coalescence of a major merger may not be required for the high luminosities of ULIRGs at z {approx} 2 as is the case locally, the large fraction (50%-73%) of interactions at all stages and potential minor mergers suggests that these processes contribute significantly to the high star formation rates of ULIRGs at z {approx} 2.

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DOE OSTI2012

THE FIRST INFRARED STUDY OF THE CLOSE ENVIRONMENT OF A LONG GAMMA-RAY BURST

We present a characterization of the close environment of GRB 980425 based on 5-160 {mu}m spectro-imaging obtained with Spitzer. The gamma-ray burst GRB 980425 occurred in a nearby (z = 0.0085) SBc-type dwarf galaxy at a projected distance of 900 pc from an H II region with strong signatures of Wolf-Rayet (WR) stars. While this 'WR region' produces less than 5% of the B-band emission of the host, we find that it is responsible for 45% {+-} 10% of the total infrared luminosity, with a maximum contribution reaching 75% at 25-30 {mu}m. This atypical property is rarely observed among morphologically relaxed dwarfs, suggesting a strong causal link with the gamma-ray burst (GRB) event. The luminosity of the WR region (L{sub 8-1000{mu}m} = 4.6 Multiplication-Sign 10{sup 8} L{sub Sun }), the peak of its spectral energy distribution at {approx}<100 {mu}m, and the presence of highly ionized emission lines (e.g., [Ne III]) also reveal extremely young (<5 Myr) star-forming activity, with a typical timescale of only 47 Myr to double the stellar mass already built. Finally, the mid-IR over B-band luminosity ratio in this region is substantially higher than in star-forming galaxies with similar L{sub IR}, but it is lower than in young dust-enshrouded stellar clusters. Considering the modest obscuration measured from the silicate features ({tau}{sub 9.7{mu}m} {approx} 0.015), this suggests that the WR region is dominated by one or several star clusters that have either partly escaped or cleared out their parent molecular cloud. Combined with the properties characterizing the whole population of GRB hosts, our results reinforce the idea that long GRBs mostly happen within or in the vicinity of relatively unobscured galactic regions harboring very recent star formation.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

MID-INFRARED PROPERTIES OF OH MEGAMASER HOST GALAXIES. I. SPITZER IRS LOW- AND HIGH-RESOLUTION SPECTROSCOPY

We present mid-infrared spectra and photometry from the Infrared Spectrograph on the Spitzer Space Telescope for 51 OH megamasers (OHMs), along with 15 galaxies confirmed to have no megamaser emission above L {sub OH} = 10{sup 2.3} L {sub sun}. The majority of galaxies display moderate-to-deep 9.7 {mu}m amorphous silicate absorption, with OHM galaxies showing stronger average absorption and steeper 20-30 {mu}m continuum emission than non-masing galaxies. Emission from multiple polycyclic aromatic hydrocarbons (PAHs), especially at 6.2, 7.7, and 11.3 {mu}m, is detected in almost all systems. Fine-structure atomic emission (including [Ne II], [Ne III], [S III], and [S IV]) and multiple H{sub 2} rotational transitions are observed in more than 90% of the sample. A subset of galaxies show emission from rarer atomic lines, such as [Ne V], [O IV], and [Fe II]. Fifty percent of the OHMs show absorption from water ice and hydrogenated amorphous carbon grains, while absorption features from CO{sub 2}, HCN, C{sub 2}H{sub 2}, and crystalline silicates are also seen in several OHMs. Column densities of OH derived from 34.6 {mu}m OH absorption are similar to those derived from 1667 MHz OH absorption in non-masing galaxies, indicating that the abundance of masing molecules is similar for both samples. This data paper presents full mid-infrared spectra for each galaxy, along with measurements of line fluxes and equivalent widths, absorption feature depths, and spectral indices.

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