scholarly journals Towards studying hierarchical assembly in real time: a Milky Way progenitor galaxy at z = 2.36 under the microscope

2020 ◽  
Vol 493 (4) ◽  
pp. 5653-5661 ◽  
Author(s):  
Tom O Zick ◽  
Daniel R Weisz ◽  
Bruno Ribeiro ◽  
Mariska T Kriek ◽  
Benjamin D Johnson ◽  
...  
Keyword(s):  
Near Infrared ◽  
Milky Way ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Star Clusters ◽  
Star Formation History ◽  
Ex Situ ◽  
Spectral Energy ◽  
Space Telescope

ABSTRACT We use Hubble Space Telescope (HST) imaging and near-infrared spectroscopy from Keck/Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) to study the substructure around the progenitor of a Milky Way-mass galaxy in the Hubble Frontier Fields (HFF). Specifically, we study an $r_\mathrm{ e} = 40^{+70}_{-30}$ pc, $M_{\star } \sim 10^{8.2} \, \mathrm{M}_{\odot }$ rest-frame ultraviolet luminous ‘clump’ at a projected distance of ∼100 pc from a M⋆ ∼ 109.8 M⊙ galaxy at z = 2.36 with a magnification μ = 5.21. We measure the star formation history of the clump and galaxy by jointly modelling the broad-band spectral energy distribution from HST photometry and Hα from MOSFIRE spectroscopy. Given our inferred properties (e.g. mass, metallicity, dust) of the clump and galaxy, we explore scenarios in which the clump formed in situ (e.g. a star-forming complex) or ex situ (e.g. a dwarf galaxy being accreted). If it formed in situ, we conclude that the clump is likely a single entity as opposed to a aggregation of smaller star clusters, making it one of the most dense star clusters catalogued. If it formed ex situ, then we are witnessing an accretion event with a 1:40 stellar mass ratio. However, our data alone are not informative enough to distinguish between in situ and ex situ scenarios to a high level of significance. We posit that the addition of high-fidelity metallicity information, such as [O iii] 4363 Å, which can be detected at modest signal-to-noise ratio with only a few hours of James Webb Space Telescope(JWST)/Near-Infrared Spectrograph (NIRSpec) time, may be a powerful discriminant. We suggest that studying larger samples of moderately lensed substructures across cosmic time can provide unique insight into the hierarchical formation of galaxies like the Milky Way.

scholarly journals Surrogate modelling the Baryonic Universe – I. The colour of star formation

2020 ◽  
Vol 495 (2) ◽  
pp. 2088-2104
Author(s):  
Jonás Chaves-Montero ◽  
Andrew Hearin
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Principal Component ◽  
Major Axis ◽  
Sloan Digital Sky Survey ◽  
Star Formation History ◽  
Spectral Energy ◽  
Colour Space

ABSTRACT The spectral energy distribution of a galaxy emerges from the complex interplay of many physical ingredients, including its star formation history (SFH), metallicity evolution, and dust properties. Using galaxpy, a new galaxy spectral prediction tool, and SFHs predicted by the empirical model universemachine and the cosmological hydrodynamical simulation IllustrisTNG, we isolate the influence of SFH on optical and near-infrared colours from 320 to 1080 Å at z = 0. By carrying out a principal component analysis, we show that physically motivated SFH variations modify galaxy colours along a single direction in colour space: the SFH-direction. We find that the projection of a galaxy’s present-day colours on to the SFH-direction is almost completely regulated by the fraction of stellar mass that the galaxy formed over the last billion years. Together with cosmic downsizing, this results in galaxies becoming redder as their host halo mass increases. We additionally study the change in galaxy colours due to variations in metallicity, dust attenuation, and nebular emission lines, finding that these properties vary broad-band colours along distinct directions in colour space relative to the SFH-direction. Finally, we show that the colours of low-redshift Sloan Digital Sky Survey galaxies span an ellipsoid with significant extent along two independent dimensions, and that the SFH-direction is well-aligned with the major axis of this ellipsoid. Our analysis supports the conclusion that variations in SFH are the dominant influence on present-day galaxy colours, and that the nature of this influence is strikingly simple.

scholarly journals The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy PKS J1222+0413

2019 ◽  
Vol 487 (1) ◽  
pp. 181-197 ◽  
Author(s):  
Daniel Kynoch ◽  
Hermine Landt ◽  
Martin J Ward ◽  
Chris Done ◽  
Catherine Boisson ◽  
...  
Keyword(s):  
Near Infrared ◽  
Uv Spectroscopy ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Physical Models ◽  
Spectral Energy ◽  
Narrow Line ◽  
Relativistic Jet ◽  
Γ Ray ◽  
Apply Physical

ABSTRACT We present a multifrequency study of PKS J1222+0413 (4C +04.42), currently the highest redshift γ-ray emitting narrow-line Seyfert 1 (γ-NLS1). We assemble a broad spectral energy distribution (SED) including previously unpublished datasets: X-ray data obtained with the NuSTAR and Neil Gehrels Swift observatories; near-infrared, optical, and UV spectroscopy obtained with VLT X-shooter; and multiband radio data from the Effelsberg telescope. These new observations are supplemented by archival data from the literature. We apply physical models to the broad-band SED, parametrizing the accretion flow and jet emission to investigate the disc–jet connection. PKS J1222+0413 has a much greater black hole mass than most other NLS1s, MBH ≈ 2 × 108 M$\odot$, similar to those found in flat spectrum radio quasars (FSRQs). Therefore this source provides insight into how the jets of γ-NLS1s relate to those of FSRQs.

scholarly journals The polarized spectral energy distribution of NGC 4151

2020 ◽  
Vol 496 (1) ◽  
pp. 215-222
Author(s):  
F Marin ◽  
J Le Cam ◽  
E Lopez-Rodriguez ◽  
M Kolehmainen ◽  
B L Babler ◽  
...  
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Far Infrared ◽  
Seyfert Galaxies ◽  
Mie Scattering ◽  
Polarization Measurement ◽  
Spectral Energy ◽  
Ngc 4151 ◽  
Near Ir

ABSTRACT NGC 4151 is among the most well-studied Seyfert galaxies that does not suffer from strong obscuration along the observer’s line of sight. This allows to probe the central active galactic nucleus (AGN) engine with photometry, spectroscopy, reverberation mapping, or interferometry. Yet, the broad-band polarization from NGC 4151 has been poorly examined in the past despite the fact that polarimetry gives us a much cleaner view of the AGN physics than photometry or spectroscopy alone. In this paper, we compile the 0.15–89.0 μm total and polarized fluxes of NGC 4151 from archival and new data in order to examine the physical processes at work in the heart of this AGN. We demonstrate that, from the optical to the near-infrared (IR) band, the polarized spectrum of NGC 4151 shows a much bluer power-law spectral index than that of the total flux, corroborating the presence of an optically thick, locally heated accretion flow, at least in its near-IR emitting radii. Specific signatures from the atmosphere of the accretion structure are tentatively found at the shortest ultraviolet (UV) wavelengths, before the onset of absorption opacity. Otherwise, dust scattering appears to be the dominant contributor from the near-UV to near-IR polarized spectrum, superimposed on to a weaker electron component. We also identify a change in the polarization processes from the near-IR to the mid-IR, most likely associated with the transition from Mie scattering to dichroic absorption from aligned dust grains in the dusty torus or narrow-line region. Finally, we present and discuss the very first far-infrared polarization measurement of NGC 4151 at 89 μm.

scholarly journals COMBO-17+4: An Optical-NIR Survey for Galaxies out to z=2

2006 ◽  
Vol 2 (S235) ◽  
pp. 419-419
Author(s):  
M-H. Nicol ◽  
K. Meisenheimer ◽  
C. Tapken ◽  
C. Wolf
Keyword(s):  
Galaxy Evolution ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Optical Data ◽  
Spectral Energy ◽  
Data Set ◽  
Infrared Observation ◽  
Redshift Range ◽  
Red Sequence

AbstractClassifying Object by Medium-Band Observations in 17 filters (COMBO-17) has already produced a very accurate picture of galaxy evolution since z~1 based on 25000 galaxies in 17 medium optical bands. We now extend the range of reliable multi-color redshifts with COMBO-17+4, a deep optical-NIR survey which will combine the existing optical data set of COMBO-17 with near infrared observation in three medium bands: Y(λ/Δλ = 1040/80nm), J1(1190/130nm) and J2(1320/130nm) and one broad band H(1650/300nm). The NIR bands extend the photometric redshift range to z~2.1. COMBO 17+4 will provide the first large sample of galaxies (>5000) at 1<z<2 with a redshifts accuracy of Δz<0.03(1+z). Three fields are observed: Abell 901, Abell 226 and the COMBO 11h-field, for a total coverage of 0.77□2 of the sky. Each COMBO 17+4 field measures 31 × 30 sqarcmin. The NIR bands are observed with the Omega2000 camera at Calar Alto Observatory in Spain.The scientific goals for this study are multiple. COMBO-17+4 will enable us to establish the luminosity function for the red sequence and blue galaxies in the redshift range 1<z<2. Also it will be possible to determine the formation history at z=2 by analyzing the width of the red sequence galaxies. Moreover this survey will provide several thousand of individual galaxy masses (with an accuracy <30%) obtained with Spectral Energy Distribution (SED) template fitting. Once the masses are obtained the mass function will provide a useful tool to test the hierarchical model of evolution of galaxies by checking whether the massive red sequence galaxies (logM>10.5) are already in place at z>1.5 (9Gyr).We present first results from the full 21 bands photometry in half of the Abell 901 field. It allows us to study not only z>1 galaxies but also the stellar content of several hundred cluster galaxies.

scholarly journals Substructure and Signs of Planet Formation in the Disk of HD 169142

2013 ◽  
Vol 8 (S299) ◽  
pp. 145-148
Author(s):  
M. Osorio ◽  
G. Anglada ◽  
C. Carrasco-González ◽  
J. M. Torrelles ◽  
P. D'Alessio ◽  
...  
Keyword(s):  
Near Infrared ◽  
Planet Formation ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Dust Emission ◽  
Central Star ◽  
Physical Structure ◽  
Spectral Energy ◽  
High Angular Resolution ◽  
Compact Source

AbstractWe carried out 7 mm VLA observations at very high angular resolution that reveal substructure and evidence of planet formation in the disk of HD 169142. Our observations, along with near-infrared polarimetric imaging, show that this disk has a ring of enhanced, asymmetric emission at a radius of ~25 AU from the central star. This ring, whose inner region appears devoid of emission, is surrounded by an annular gap in surface density in the ~30-70 AU range of radii. Several mechanisms have been invoked in the literature to explain this kind of gaps and cavities. Among them, one of the most interesting is the possibility that one or more planets in formation are creating these cavities. Since our 7 mm observations show a compact source lying in the 30-70 AU gap, we speculate that this compact source could be tracing dust emission associated with a possible protoplanet. We model the broad-band spectral energy distribution of the disk and we infer its physical structure. From this modeling we infer the presence of a small (r ~ 0.7 AU) disk inside the central cavity, suggesting that the HD 169142 disk is in the pre-transitional disk phase.

scholarly journals Constraining the Milky Way’s ultraviolet to infrared SED with Gaussian Process Regression

2021 ◽  
Author(s):  
Catherine E Fielder ◽  
Jeffrey A Newman ◽  
Brett H Andrews ◽  
Gail Zasowski ◽  
Nicholas F Boardman ◽  
...  
Keyword(s):  
Star Formation ◽  
Gaussian Process ◽  
Milky Way ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Gaussian Process Regression ◽  
Axial Ratio ◽  
Star Formation History ◽  
Spectral Energy ◽  
Star Forming

Abstract Improving our knowledge of global Milky Way (MW) properties is critical for connecting the detailed measurements only possible from within our Galaxy to our understanding of the broader galaxy population. We here train Gaussian Process Regression (GPR) models on SDSS galaxies to map from galaxy properties (stellar mass, apparent axial ratio, star formation rate, bulge-to-total ratio, disk scale length, and bar vote fraction) to UV (GALEX FUV/NUV), optical (SDSS ugriz) and IR (2MASS JHKs and WISE W1/W2/W3/W4) fluxes and uncertainties. With these models we estimate the photometric properties of the MW, resulting in a full UV-to-IR spectral energy distribution (SED) as it would be measured externally, viewed face-on. We confirm that the Milky Way lies in the green valley in optical diagnostic diagrams, but show for the first time that the MW is in the star-forming region in standard UV and IR diagnostics—characteristic of the population of red spiral galaxies. Although our GPR method predicts one band at a time, the resulting MW UV–IR SED is consistent with SEDs of local spirals with characteristics broadly similar to the MW, suggesting that these independent predictions can be combined reliably. Our UV–IR SED will be invaluable for reconstructing the MW’s star formation history using the same tools employed for external galaxies, allowing comparisons of results from in situ measurements to those from the methods used for extra-galactic objects.

scholarly journals Particle acceleration in low-power hotspots: modelling the broad-band spectral energy distribution

2020 ◽  
Vol 495 (2) ◽  
pp. 1593-1607 ◽  
Author(s):  
G Migliori ◽  
M Orienti ◽  
L Coccato ◽  
G Brunetti ◽  
F D’Ammando ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Energy Distribution ◽  
Low Power ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Radiative Processes

ABSTRACT The acceleration and radiative processes active in low-power radio hotspots are investigated by means of new deep near-infrared (NIR) and optical Very Large Telescope (VLT) observations, complemented with archival, high-sensitivity VLT, radio Very Large Array (VLA), and X-ray Chandra data. For the three studied radio galaxies (3C 105, 3C 195, and 3C 227), we confirm the detection of NIR/optical counterparts of the observed radio hotspots. We resolve multiple components in 3C 227 West and in 3C 105 South and characterize the diffuse NIR/optical emission of the latter. We show that the linear size of this component (≳4 kpc) makes 3C 105 South a compelling case for particles’ re-acceleration in the post-shock region. Modelling of the radio-to-X-ray spectral energy distribution (SED) of 3C 195 South and 3C 227 W1 gives clues on the origin of the detected X-ray emission. In the context of inverse Compton models, the peculiarly steep synchrotron curve of 3C 195 South sets constraints on the shape of the radiating particles’ spectrum that are testable with better knowledge of the SED shape at low (≲GHz) radio frequencies and in X-rays. The X-ray emission of 3C 227 W1 can be explained with an additional synchrotron component originating in compact (&lt;100 pc) regions, such those revealed by radio observations at 22 GHz, provided that efficient particle acceleration (γ ≳ 107) is ongoing. The emerging picture is that of systems in which different acceleration and radiative processes co-exist.

scholarly journals Optical and Near Infrared Observations of Post-AGB Stars

1998 ◽  
Vol 11 (1) ◽  
pp. 383-383
Author(s):  
T. Fujii ◽  
T. Ono ◽  
Y. Nakada ◽  
M. Parthasarathy
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Asymptotic Giant Branch ◽  
Spectral Energy ◽  
Agb Stars ◽  
Ir Camera ◽  
Infrared Observations ◽  
Infrared Wavelengths ◽  
Band Spectra

The post-AGB stars rapidly change their spectral energy distribution on their way from the asymptotic giant branch(AGB) to planetary nebula stage. They are generally surrounded by cool and extended dust shells emitting largely in the infrared wavelengths. A selected sample of the post-AGB candidates were observed using the CCDand IR camera at Kiso and Nishi-Harima Astronomical Observatory. They were classified based on their broad band spectra from B to K’ band and their evolutionary stages have been discussed using the simple model of the dust shell around a star. The light variation of some of these objects were monitored and their light curves are also presented.

scholarly journals The effects of star formation history in the SFR–M* relation of H ii galaxies

2020 ◽  
Vol 500 (3) ◽  
pp. 3240-3253
Author(s):  
Amanda R Lopes ◽  
Eduardo Telles ◽  
Jorge Melnick
Keyword(s):  
Star Formation ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Star Formation History ◽  
Spectral Energy ◽  
Distribution Fitting ◽  
Good Tool ◽  
Star Forming ◽  
Additional Information ◽  
Star Formation Histories

ABSTRACT We discuss the implications of assuming different star formation histories (SFH) in the relation between star formation rate (SFR) and mass derived by the spectral energy distribution fitting (SED). Our analysis focuses on a sample of H ii galaxies, dwarf starburst galaxies spectroscopically selected through their strong narrow emission lines in SDSS DR13 at z &lt; 0.4, cross-matched with photometric catalogues from GALEX, SDSS, UKIDSS, and WISE. We modelled and fitted the SEDs with the code CIGALE adopting different descriptions of SFH. By adding information from different independent studies, we find that H ii galaxies are best described by episodic SFHs including an old (10 Gyr), an intermediate age (100−1000 Myr) and a recent population with ages &lt; 10 Myr. H ii galaxies agree with the SFR−M* relation from local star-forming galaxies, and only lie above such relation when the current SFR is adopted as opposed to the average over the entire SFH. The SFR−M* demonstrated not to be a good tool to provide additional information about the SFH of H ii galaxies, as different SFH present a similar behaviour with a spread of &lt;0.1 dex.

scholarly journals Accretion and Outflow Activity in the Earliest Phases of Star-Formation: CO, Sub-mm Continuum, and Near-Infrared Observations

1997 ◽  
Vol 163 ◽  
pp. 725-726
Author(s):  
K.-W. Hodapp ◽  
E. F. Ladd
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
Point Sources ◽  
Spectral Energy ◽  
Infrared Observations ◽  
Circumstellar Material ◽  
Dense Cores ◽  
Wavelength Radiation ◽  
Main Component

Stars in the earliest phases of their formation, i.e., those accreting the main component of their final mass, are deeply embedded within dense cores of dust and molecular material. Because of the high line-of-sight extinction and the large amount of circumstellar material, stellar emission is reprocessed by dust into long wavelength radiation, typically in the far-infrared and sub-millimeter bands. Consequently, the youngest sources are strong submillimeter continuum sources, and often undetectable as point sources in the near-infrared and optical. The most deeply embedded of these sources have been labelled “Class 0” sources by André, Ward-Thompson, & Barsony (1994), in an extension of the spectral energy distribution classification scheme first proposed by Adams, Lada, & Shu (1987).

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