arXiv subjects

R. Zylka

Publications and source records attributed to R. Zylka.

At least 37 records · Page 2Linked to original sources

arXiv2023

Exploring the interstellar medium of NGC 891 at millimeter wavelengths using the NIKA2 camera

In the framework of the IMEGIN Large Program, we used the NIKA2 camera on the IRAM 30-m telescope to observe the edge-on galaxy NGC 891 at 1.15 mm and 2 mm and at a FWHM of 11.1" and 17.6", respectively. Multiwavelength data enriched with the new NIKA2 observations fitted by the HerBIE SED code (coupled with the THEMIS dust model) were used to constrain the physical properties of the ISM. Emission originating from the diffuse dust disk is detected at all wavelengths from mid-IR to mm, while mid-IR observations reveal warm dust emission from compact HII regions. Indications of mm excess emission have also been found in the outer parts of the galactic disk. Furthermore, our SED fitting analysis constrained the mass fraction of the small (< 15 Angstrom) dust grains. We found that small grains constitute 9.5% of the total dust mass in the galactic plane, but this fraction increases up to ~ 20% at large distances (|z| > 3 kpc) from the galactic plane.

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arXiv2023

Constraining Millimeter Dust Emission in Nearby Galaxies with NIKA2: the case of NGC2146 and NGC2976

This study presents the first millimeter continuum mapping observations of two nearby galaxies, the starburst spiral galaxy NGC2146 and the dwarf galaxy NGC2976, at 1.15 mm and 2 mm using the NIKA2 camera on the IRAM 30m telescope, as part of the Guaranteed Time Large Project IMEGIN. These observations provide robust resolved information about the physical properties of dust in nearby galaxies by constraining their FIR-radio SED in the millimeter domain. After subtracting the contribution from the CO line emission, the SEDs are modeled spatially using a Bayesian approach. Maps of dust mass surface density, temperature, emissivity index, and thermal radio component of the galaxies are presented, allowing for a study of the relations between the dust properties and star formation activity (using observations at 24$μ$m as a tracer). We report that dust temperature is correlated with star formation rate in both galaxies. The effect of star formation activity on dust temperature is stronger in NGC2976, an indication of the thinner interstellar medium of dwarf galaxies. Moreover, an anti-correlation trend is reported between the dust emissivity index and temperature in both galaxies.

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arXiv2023

NIKA2 observations of starless cores in Taurus and Perseus

Dusty starless cores play an important role in regulating the initial phases of the formation of stars and planets. In their interiors, dust grains coagulate and ice mantles form, thereby changing the millimeter emissivities and hence the ability to cool. We mapped four regions with more than a dozen cores in the nearby Galactic filaments of Taurus and Perseus using the NIKA2 camera at the IRAM 30-meter telescope. Combining the 1mm to 2mm flux ratio maps with dust temperature maps from Herschel allowed to create maps of the dust emissivity index $β_{1,2}$ at resolutions of 2430 and 5600 a.u. in Taurus and Perseus, respectively. Here, we study the variation with total column densities and environment. $β_{1,2}$ values at the core centers ($A_V=12-19$mag) vary significantly between $\sim1.1$ and $2.3$. Several cores show a strong rise of $β_{1,2}$ from the outskirts at $\sim4$mag to the peaks of optical extinctions, consistent with the predictions of grain models and the gradual build-up of ice mantles on coagulated grains in the dense interiors of starless cores.

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arXiv2023

The stratification of ISM properties in the edge-on galaxy NGC 891 revealed by NIKA2

As the millimeter wavelength range remains a largely unexplored spectral region for galaxies, the IMEGIN large program aims to map the millimeter continuum emission of 22 nearby galaxies at 1.15 and 2 mm. Using the high-resolution maps produced by the NIKA2 camera, we explore the existence of very cold dust and take possible contamination by free-free and synchrotron emission into account. We study the IR-to-radio emission coming from different regions along the galactic plane and at large vertical distances. New observations of NGC 891, using the NIKA2 camera on the IRAM 30m telescope, along with a suite of observations at other wavelengths were used to perform a multiwavelength study of the spectral energy distribution in the interstellar medium in this galaxy. This analysis was performed globally and locally, using the advanced hierarchical Bayesian fitting code, HerBIE, coupled with the THEMIS dust model. Our dust modeling is able to reproduce the near-IR to millimeter emission of NGC 891, with the exception of an excess at a level of 25% obtained by the NIKA2 observations in the outermost parts of the disk. The radio continuum and thermal dust emission are distributed differently in the disk and galaxy halo. Different dusty environments are also revealed by a multiwavelength investigation of the emission features. Our detailed decomposition at millimeter and centimeter wavelengths shows that emission at 1 mm is purely originated by dust. Radio components become progressively important with increasing wavelengths. Finally, we find that emission arising from small dust grains accounts for ~ 9.5% of the total dust mass, reaching up to 20% at large galactic latitudes. Shock waves in the outflows that shatter the dust grains might explain this higher fraction of small grains in the halo.

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arXiv2023

NIKA2 Cosmological Legacy Survey: Survey Description and Galaxy Number Counts

Aims. Deep millimeter surveys are necessary to probe the dust-obscured galaxies at high redshift. We conducted a large observing program at 1.2 and 2 mm with the NIKA2 camera installed on the IRAM 30-meter telescope. This NIKA2 Cosmological Legacy Survey (N2CLS) covers two emblematic fields: GOODS-N and COSMOS. We introduce the N2CLS survey and present new 1.2 and 2 mm number count measurements based on the tiered N2CLS observations from October 2017 to May 2021. Methods. We develop an end-to-end simulation that combines an input sky model with the instrument noise and data reduction pipeline artifacts. This simulation is used to compute the sample purity, flux boosting, pipeline transfer function, completeness, and effective area of the survey. We used the 117 deg$^2$ SIDES simulations as the sky model, which include the galaxy clustering. Our formalism allows us to correct the source number counts to obtain galaxy number counts, the difference between the two being due to resolution effects caused by the blending of several galaxies inside the large beam of single-dish instruments. Results. The N2CLS-May2021 survey reaches an average 1-$σ$ noise level of 0.17 and 0.048 mJy on GOODS-N over 159 arcmin$^2$, and 0.46 and 0.14 mJy on COSMOS over 1010 arcmin$^2$, at 1.2 and 2 mm, respectively. For a purity threshold of 80%, we detect 120 and 67 sources in GOODS-N and 195 and 76 sources in COSMOS, at 1.2 and 2 mm, respectively. Our measurement connects the bright single-dish to the deep interferometric number counts. After correcting for resolution effects, our results reconcile the single-dish and interferometric number counts and are further accurately compared with model predictions.

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arXiv2022

Candidate cosmic filament in the GJ526 field, mapped with the NIKA2 camera

Distinctive large-scale structures have been identified in the spatial distribution of optical galaxies up to redshift z ~ 1. In the more distant universe, the relationship between the dust-obscured population of star-forming galaxies observed at millimetre wavelengths and the network of cosmic filaments of dark matter apparent in all cosmological hydrodynamical simulations is still under study. Using the NIKA2 dual-band millimetre camera, we mapped a field of ~ 90 arcminutes^2 in the direction of the star GJ526 simultaneously in its 1.15-mm and 2.0-mm continuum wavebands to investigate the nature of the quasi-alignment of five sources found ten years earlier with the MAMBO camera at 1.2 mm. We find that these sources are not clumps of a circumstellar debris disc around this star as initially hypothesized. Rather, they must be dust-obscured star-forming galaxies, or sub-millimetre galaxies (SMGs), in the distant background. The new NIKA2 map at 1.15 mm reveals a total of seven SMGs distributed in projection on the sky along a filament-like structure crossing the whole observed field. Furthermore, we show that the NIKA2 and supplemental Herschel photometric data are compatible with a model of the spectral energy distributions (SEDs) of these sources when a common redshift of 2.5 and typical values of the dust parameters for SMGs are adopted. Hence, we speculate that these SMGs might be located in a filament of the distant `cosmic web'. The length of this candidate cosmic filament crossing the whole map is at least 4 cMpc (comoving), and the separations between sources are between 0.25 cMpc and 1.25 cMpc at this redshift, in line with expectations from cosmological simulations. Nonetheless, further observations to determine the precise spectroscopic redshifts of these sources are required to definitively support this hypothesis of SMGs embedded in a cosmic filament of dark matter.

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arXiv2021

Galactic Star Formation with NIKA2 (GASTON): Evidence of mass accretion onto dense clumps

High-mass stars ($m_* \gtrsim 8 \, M_\odot$) play a crucial role in the evolution of galaxies, and so it is imperative that we understand how they are formed. We have used the New IRAM KIDs Array 2 (NIKA2) camera on the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope to conduct high-sensitivity continuum mapping of $\sim2$ deg$^2$ of the Galactic plane (GP) as part of the Galactic Star Formation with NIKA2 (GASTON) large program. We have identified a total of 1467 clumps within our deep 1.15 mm continuum maps and, by using overlapping continuum, molecular line, and maser parallax data, we have determined their distances and physical properties. By placing them upon an approximate evolutionary sequence based upon 8 $μ$m $\textit{Spitzer}$ imaging, we find evidence that the most massive dense clumps accrete material from their surrounding environment during their early evolution, before dispersing as star formation advances, supporting clump-fed models of high-mass star formation.

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arXiv2021

Probing the role of magnetic fields in star-forming filaments: NIKA2-Pol commissioning results toward OMC-1

Dust polarization observations are a powerful, practical tool to probe the geometry (and to some extent, the strength) of magnetic fields in star-forming regions. In particular, Planck polarization data have revealed the importance of magnetic fields on large scales in molecular clouds. However, due to insufficient resolution, Planck observations are unable to constrain the B-field geometry on prestellar and protostellar scales. The high angular resolution of 11.7 arcsec provided by NIKA2-Pol 1.15 mm polarimetric imaging, corresponding to $\sim$ 0.02 pc at the distance of the Orion molecular cloud (OMC), makes it possible to advance our understanding of the B-field morphology in star-forming filaments and dense cores (IRAM 30m large program B-FUN). The commissioning of the NIKA2-Pol instrument has led to several challenging issues, in particular, the instrumental polarization or intensity-to-polarization (leakage) effect. In the present paper, we illustrate how this effect can be corrected for, leading to reliable exploitable data in a structured, extended source such as OMC-1. We present a statistical comparison between NIKA2-Pol and SCUBA2-Pol2 results in the OMC-1 region. We also present tentative evidence of local pinching of the B-field lines near Orion-KL, in the form of a new small-scale hourglass pattern, in addition to the larger-scale hourglass already seen by other instruments such as Pol2.

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arXiv2021

Dust Emission in Galaxies at Millimeter Wavelengths: Cooling of star forming regions in NGC6946

Interstellar dust plays an important role in the formation of molecular gas and the heating and cooling of the interstellar medium. The spatial distribution of the mm-wavelength dust emission from galaxies is largely unexplored. The NIKA2 Guaranteed Time Project IMEGIN (Interpreting the Millimeter Emission of Galaxies with IRAM and NIKA2) has recently mapped the mm emission in the grand design spiral galaxy NGC6946. By subtracting the contributions from the free-free, synchrotron, and CO line emission, we map the distribution of the pure dust emission at 1:15mm and 2mm. Separating the arm/interarm regions, we find a dominant 2mm emission from interarms indicating the significant role of the general interstellar radiation field in heating the cold dust. Finally, we present maps of the dust mass, temperature, and emissivity index using the Bayesian MCMC modeling of the spectral energy distribution in NGC6946.

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arXiv2021

Galactic star formation with NIKA2 (GASTON): Filament convergence and its link to star formation

In the past decade filaments have been recognised as a major structural element of the interstellar medium, the densest of these filaments hosting the formation of most stars. In some star-forming molecular clouds converging networks of filaments, also known as hub filament systems, can be found. These hubs are believed to be preferentially associated to massive star formation. As of today, there are no metrics that allow the systematic quantification of a filament network convergence. Here, we used the IRAM 30m NIKA2 observations of the Galactic plane from the GASTON large programme to systematically identify filaments and produce a filament convergence parameter map. We use such a map to show that: i. hub filaments represent a small fraction of the global filament population; ii. hubs host, in proportion, more massive and more luminous compact sources that non-hubs; iii. hub-hosting clumps are more evolved that non-hubs; iv. no discontinuities are observed in the properties of compact sources as a function of convergence parameter. We propose that the rapid global collapse of clumps is responsible for (re)organising filament networks into hubs and, in parallel, enhancing the mass growth of compact sources.

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arXiv2021

Crab nebula at 260 GHz with the NIKA2 polarimeter. Implications for the polarization angle calibration of future CMB experiments

The quest for primordial gravitational waves enclosed in the Cosmic Microwave Background (CMB) polarization B-modes signal motivates the development of a new generation of high sensitive experiments (e.g. CMB-S4, LiteBIRD) that would allow them to detect its imprint.Neverthless, this will be only possible by ensuring a high control of the instrumental systematic effects and an accurate absolute calibration of the polarization angle. The Crab nebula is known to be a polarization calibrator on the sky for CMB experiments, already used for the Planck satellite it exhibits a high polarized signal at microwave wavelengths. In this work we present Crab polarization observations obtained at the central frequency of 260 GHz with the NIKA2 instrument and discuss the accuracy needed on such a measurement to improve the constraints on the absolute angle calibration for CMB experiments.

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arXiv2021

Exploring the millimetre emission in nearby galaxies: analysis of the edge-on galaxy NGC 891

New observations of the edge-on galaxy NGC 891, at 1.15 and 2 mm obtained with the IRAM 30-m telescope and the NIKA2 camera, within the framework of the IMEGIN (Interpreting the Millimetre Emission of Galaxies with IRAM and NIKA2) Large Program, are presented in this work. By using multiwavelength maps (from the mid-IR to the cm wavelengths) we perform SED fitting in order to extract the physical properties of the galaxy on both global and local ($\sim$kpc) scales. For the interpretation of the observations we make use of a state-of-the-art SED fitting code, HerBIE (HiERarchical Bayesian Inference for dust Emission). The observations indicate a galaxy morphology, at mm wavelengths, similar to that of the cold dust emission traced by sub-mm observations and to that of the molecular gas. The contribution of the radio emission at the NIKA2 bands is very small (negligible at 1.15 mm and $\sim10\%$ at 2 mm) while it dominates the total energy budget at longer wavelengths (beyond 5 mm). On local scales, the distribution of the free-free emission resembles that of the dust thermal emission while the distribution of the synchrotron emission shows a deficiency along the major axis of the disc of the galaxy.

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arXiv2021

Overdensity of SubMillimiter Galaxies in the GJ526 Field mapped with the NIKA2 Camera

Using the NIKA2 dual band millimeter camera installed on the IRAM30m telescope, we have mapped a relatively large field (~70 arcmin^2) in the direction of the star GJ526 to investigate the nature of the sources found with the MAMBO camera at 1.2 mm ten years earlier. We have found that they must be dust-obscured galaxies (SMGs) in the background beyond the star. The new NIKA2 map at 1.15 mm reveals additional sources and, in fact, an overdensity of SMGs predominantly distributed along a filament-like structure in projection on the sky across the whole observed field. We speculate this might be a cosmic filament at high redshift as revealed in cosmological hydrodynamical simulations. Measurement of spectroscopic redshifts of the SMGs in the candidate filament is required now for a definitive confirmation of the nature of the structure.

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arXiv2021

Mapping the intracluster medium temperature in the era of NIKA2 and MUSTANG-2

We present preliminary results from an on-going program that aims at mapping the intracluster medium (ICM) temperature of high redshift galaxy clusters from the MaDCoWS sample using a joint analysis of shallow X-ray data obtained by $Chandra$ and high angular resolution Sunyaev-Zel'dovich (SZ) observations realized with the NIKA2 and MUSTANG-2 cameras. We also present preliminary results from an on-going Open Time program within the NIKA2 collaboration that aims at mapping the ICM temperature of a galaxy cluster at $z=0.45$ from the resolved detection of the relativistic corrections to the SZ spectrum. These studies demonstrate how high angular resolution SZ observations will play a major role in the coming decade to push the investigation of ICM dynamics and non-gravitational processes to high redshift before the next generation X-ray observatories come into play.

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arXiv2021

Searching for high-z DSFGs with NIKA2 and NOEMA

As the possible progenitors of passive galaxies at z=2-3, dusty star-forming galaxies (DSFGs) at z>4 provide a unique perspective to study the formation, assembly, and early quenching of massive galaxies in the early Universe. The extreme obscuration in optical-IR makes (sub)mm spectral scans the most universal and unbiased way to confirm/exclude the high-z nature of candidate dusty star-forming galaxies. We present here the status of the NIKA2 Cosmological Legacy Survey (N2CLS), which is the deepest wide-area single-dish survey in the millimeter searching for high-z DSFGs. We also introduce a joint-analysis method to efficiently search for the spectroscopic redshift of high-z DSFGs with noisy spectra and photometric data and present its success in identifying the redshift of DSFGs found in NIKA2 science verification data.

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arXiv2020

Cluster cosmology with the NIKA2 SZ Large Program

The main limiting factor of cosmological analyses based on thermal Sunyaev-Zel'dovich (SZ) cluster statistics comes from the bias and systematic uncertainties that affect the estimates of the mass of galaxy clusters. High-angular resolution SZ observations at high redshift are needed to study a potential redshift or morphology dependence of both the mean pressure profile and of the mass-observable scaling relation used in SZ cosmological analyses. The NIKA2 camera is a new generation continuum instrument installed at the IRAM 30-m telescope. With a large field of view, a high angular resolution and a high-sensitivity, the NIKA2 camera has unique SZ mapping capabilities. In this paper, we present the NIKA2 SZ large program, aiming at observing a large sample of clusters at redshifts between 0.5 and 0.9, and the characterization of the first cluster oberved with NIKA2.

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arXiv2020

Calibration and Performance of the NIKA2 camera at the IRAM 30-meter Telescope

NIKA2 is a dual-band millimetric continuum camera of 2900 Kinetic Inductance Detectors (KID), operating at $150$ and $260\,\rm{GHz}$, installed at the IRAM 30-meter telescope. We present the performance assessment of NIKA2 after one year of observation using a dedicated point-source calibration method, referred to as the \emph{baseline} method. Using a large data set acquired between January 2017 and February 2018 that span the whole range of observing elevations and atmospheric conditions encountered at the IRAM 30-m telescope, we test the stability of the performance parameters. We report an instantaneous field of view (FOV) of 6.5' in diameter, filled with an average fraction of $84\%$ and $90\%$ of valid detectors at $150$ and $260\,\rm{GHz}$, respectively. The beam pattern is characterized by a FWHM of $17.6'' \pm 0.1''$ and $11.1''\pm 0.2''$, and a beam efficiency of $77\% \pm 2\%$ and $55\% \pm 3\%$ at $150$ and $260\,\rm{GHz}$, respectively. The rms calibration uncertainties are about $3\%$ at $150\,\rm{GHz}$ and $6\%$ at $260\,\rm{GHz}$. The absolute calibration uncertainties are of $5\%$ and the systematic calibration uncertainties evaluated at the IRAM 30-m reference Winter observing conditions are below $1\%$ in both channels. The noise equivalent flux density (NEFD) at $150$ and $260\,\rm{GHz}$ are of $9 \pm 1\, \rm{mJy}\cdot s^{1/2}$ and $30 \pm 3\, \rm{mJy}\cdot s^{1/2}$. This state-of-the-art performance confers NIKA2 with mapping speeds of $1388 \pm 174$ and $111 \pm 11 \,\rm{arcmin}^2\cdot \rm{mJy}^{-2}\cdot \rm{h}^{-1}$ at $150$ and $260\,\rm{GHz}$. With these unique capabilities of fast dual-band mapping at high (better that 18'') angular resolution, NIKA2 is providing an unprecedented view of the millimetre Universe.

astro-ph.IM↗

arXiv2019

Observing with NIKA2Pol from the IRAM 30m telescope. Early results on the commissioning phase

The NIKA2 polarization channel at 260 GHz (1.15 mm) has been proposed primarily to observe galactic star-forming regions and probe the critical scales between 0.01-0.05 pc at which magnetic field lines may channel the matter of interstellar filaments into growing dense cores. The NIKA2 polarimeter consists of a room temperature continuously rotating multi-mesh HWP and a cold polarizer that separates the two orthogonal polarizations onto two 260 GHz KIDs arrays. We describe in this paper the preliminary results obtained during the most recent commissioning campaign performed in December 2018. We concentrate here on the analysis of the extended sources, while the observation of compact sources is presented in a companion paper [12]. We present preliminary NIKA2 polarization maps of the Crab nebula. We find that the integrated polarization intensity flux measured by NIKA2 is consistent with expectations.In terms of polarization angle, we are still limited by systematic uncertainties that will be further investigated in the forthcoming commissioning campaigns.

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