scholarly journals Counts and Colors of Faint Galaxies

1980 ◽  
Vol 92 ◽  
pp. 9-15
Author(s):  
Richard G. Kron
Keyword(s):  
Galaxy Evolution ◽  
Rest Frame ◽  
Spectral Energy ◽  
Measured Quantity ◽  
Energy Distributions ◽  
Color Distribution ◽  
Number Magnitude ◽  
Redshift Galaxy ◽  
Wide Range ◽  
Apparent Color

The color distribution of faint galaxies is an observational dimension which has not yet been fully exploited, despite the important constraints obtainable for galaxy evolution and cosmology. Number-magnitude counts alone contain very diluted information about the state of things because galaxies from a wide range in redshift contribute to the counts at each magnitude. The most-frequently-seen type of galaxy depends on the luminosity function and the relative proportions of galaxies of different spectral classes. The addition of color as a measured quantity can thus considerably sharpen the interpretation of galaxy counts since the apparent color depends on the redshift and rest-frame spectrum. To a first approximation two colors for a galaxy can determine a redshift and a spectral class, because redshift loci in a color-color diagram run roughly parallel to each other, and roughly perpendicular to the zero-redshift galaxy “main sequence” (Tinsley 1977a, Pence 1976) for small redshift. This game becomes more and more uncertain at higher redshift, because the systematics of galaxy UV spectral energy distributions are not well known, and what is known is not well understood (Code and Welch 1979). Redshifts for some random sample of faint galaxies is required to pin down the color-redshift relations; steps in this direction have already been taken by E. Turner. The reason for stressing colors, as opposed to redshifts, is that colors can be obtained relatively easily for large samples of faint galaxies if panoramic detectors are used: indeed, colors are not much more difficult to obtain than magnitudes.

scholarly journals Observations by GMRT at 323 MHz of radio-loud quasars at z  >  5

2020 ◽  
Vol 641 ◽  
pp. A85
Author(s):  
Yali Shao ◽  
Jeff Wagg ◽  
Ran Wang ◽  
Chris L. Carilli ◽  
Dominik A. Riechers ◽  
...  
Keyword(s):  
Power Law ◽  
Rest Frame ◽  
Low Frequency ◽  
Point Sources ◽  
Radio Continuum ◽  
Spectral Energy ◽  
Synchrotron Emission ◽  
Energy Distributions ◽  
Radio Range ◽  
Wide Range

We present Giant Metrewave Radio Telescope (GMRT) 323 MHz radio continuum observations toward 13 radio-loud quasars at z >  5, sampling the low-frequency synchrotron emission from these objects. Among the 12 targets successfully observed, we detected 10 above 4σ significance, while 2 remain undetected. All of the detected sources appear as point sources. Combined with previous radio continuum detections from the literature, 9 quasars have power-law spectral energy distributions throughout the radio range; for some the flux density drops with increasing frequency while it increases for others. Two of these sources appear to have spectral turnover. For the power-law-like sources, the power-law indices have a positive range between 0.18 and 0.67 and a negative values between −0.90 and −0.27. For the turnover sources, the radio peaks around ∼1 and ∼10 GHz in the rest frame, the optically thin indices are −0.58 and −0.90, and the optically thick indices are 0.50 and 1.20. A magnetic field and spectral age analysis of SDSS J114657.59+403708.6 at z = 5.01 may indicate that the turnover is not caused by synchrotron self-absorption, but rather by free-free absorption by the high-density medium in the nuclear region. Alternatively, the apparent turnover may be an artifact of source variability. Finally, we calculated the radio loudness R2500 Å for our sample, which spans a very wide range from 12−13+13 to 4982−254+279.

scholarly journals Spectral energy distribution similarity of the local galaxies and the 3.6 μm selected galaxies from the Spitzer Extended Deep Survey

2021 ◽  
Vol 21 (10) ◽  
pp. 260
Author(s):  
Cheng Cheng ◽  
Jia-Sheng Huang ◽  
Hai Xu ◽  
Gao-Xiang Jin ◽  
Chuan He ◽  
...  
Keyword(s):  
High Redshift ◽  
Spectral Energy Distribution ◽  
Mass Function ◽  
Spectral Energy ◽  
Energy Distributions ◽  
Mid Infrared ◽  
Redshift Galaxy ◽  
The Galaxy ◽  
Deep Survey ◽  
Multi Wavelength

Abstract The Spitzer Extended Deep Survey (SEDS) as a deep and wide mid-infrared (MIR) survey project provides a sample of 500 000+ sources spreading 1.46 square degree and a depth of 26 AB mag (3σ). Combining with the previous available data, we build a PSF-matched multi-wavelength photometry catalog from u band to 8 μm. We fit the SEDS galaxies spectral energy distributions by the local galaxy templates. The results show that the SEDS galaxy can be fitted well, indicating the high redshift galaxy (z ∼ 1) shares the same templates with the local galaxies. This study would facilitate the further study of the galaxy luminosity and high redshift mass function.

scholarly journals ISO Observations of AGN and Ultraluminous IR Galaxies

1998 ◽  
Vol 11 (2) ◽  
pp. 1131-1133 ◽  
Author(s):  
Alan F. M. Moorwood
Keyword(s):  
Ionization Potential ◽  
Elliptical Galaxy ◽  
Emission Lines ◽  
Spectral Energy ◽  
High Excitation ◽  
Low Resolution ◽  
Energy Distributions ◽  
Diagnostic Features ◽  
Wide Range ◽  
First Time

All the ISO instruments are contributing to the study of activity in galaxies of essentially all types. Although AGN's as such are pointlike, the beautiful CAM image of CenA shown by Catherine Cesarsky has given us the clearest view so far of its visually obscured nucleus and surrounding spiral disc embedded in an elliptical galaxy. The CAM CVF is also providing spectral images of the PAH features and important diagnostic ionic lines (e.g [NeII] and [NeIII]) in the circumnuclar regions of AGN and merging starburst systems (Vigroux et al., 1996). PHT is providing detailed spectral energy distributions over the complete 2.5-240µm range and PHTS is proving invaluable for assembling a catalogue of low resolution (R ⋍ 90) galaxy spectra covering the 6-12µm PAH features. SWS and LWS are generating higher resolution (R ⋍ 2000-200) spectra over the range 2.5-200µm such as that shown in Fig. 1. of the Circinus galaxy which exhibits both AGN and starburst activity and well illustrates the wide range of diagnostic features, many seen for the first time, accessible to ISO studies of galaxies. It shows the overall continuum with a peak around 100µm; PAH features and Si absorption which dominate the spectrum around 10µm; H recombination lines; H2 pure rotational emission lines; low ionization potential ionic lines excited by starburst activity and high excitation lines (up to ⋍ 300eV) excited by the visually obscured AGN.

scholarly journals THE REST-FRAME UV-TO-OPTICAL COLORS AND SPECTRAL ENERGY DISTRIBUTIONS OFz∼ 4-7 GALAXIES

2012 ◽  
Vol 755 (2) ◽  
pp. 148 ◽  
Author(s):  
Valentino González ◽  
Rychard J. Bouwens ◽  
Ivo Labbé ◽  
Garth Illingworth ◽  
Pascal Oesch ◽  
...  
Keyword(s):  
Rest Frame ◽  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions

scholarly journals Spectroscopy with the JWST Advanced Deep Extragalactic Survey (JADES) - the NIRSpec/NIRCAM GTO galaxy evolution project

2019 ◽  
Vol 15 (S352) ◽  
pp. 342-346
Author(s):  
Andrew J. Bunker
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Rest Frame ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Spectral Energy ◽  
Balmer Line ◽  
Chemical Abundances ◽  
Star Forming

AbstractI present an overview of the JWST Advanced Deep Extragalactic Survey (JADES), a joint program of the JWST/NIRCam and NIRSpec Guaranteed Time Observations (GTO) teams involving 950 hours of observation. We will target two well-studied fields with excellent supporting data (e.g., from HST-CANDELS): GOODS-North and South, including the Ultra Deep Field. The science goal of JADES is to chart galaxy evolution at z > 2, and potentially out to z > 10, using the rest-frame optical and near-IR though observations from ≍ 1–5μm. Multi-colour NIRCam imaging with 9 filters will enable photometric redshifts and the application of the Lyman break technique out to unprecedented distances. NIRSpec spectroscopy (with spectral resolving powers of R = 100, 1000 & 2700) will measure secure spectroscopic redshifts of the photometrically-selected population, as well as stellar continuum slopes in the UV rest-frame, and hence study the role of dust, stellar population age, and other effects. Measuring emission lines can constrain the dust extinction, star formation rates, metallicity, chemical abundances, ionization and excitation mechanism in high redshift galaxies. Coupling NIRCam and NIRSpec observations will determine stellar populations (age, star formation histories, abundances) of galaxies and provide the information to correct their broad-band spectral energy distribution for likely line contamination. Potentially we can search for signatures of Population III stars such as HeII. We can address the contribution of star-forming galaxies at z > 7 to reionization by determining the faint end slope of the luminosity function and investigating the escape fraction of ionizing photons by comparing the UV stellar continuum with the Balmer-line fluxes.

scholarly journals Overdensity of SMGs in fields containing z ∼ 0.3 galaxies: magnification bias and the implications for studies of galaxy evolution

2020 ◽  
Vol 498 (4) ◽  
pp. 4635-4649
Author(s):  
L Dunne ◽  
L Bonavera ◽  
J Gonzalez-Nuevo ◽  
S J Maddox ◽  
C Vlahakis
Keyword(s):  
Galaxy Evolution ◽  
Cross Correlation ◽  
High Redshift ◽  
Spectral Energy ◽  
Complete Sample ◽  
Energy Distributions ◽  
Statistical Measures ◽  
Luminosity Functions ◽  
Significant Contamination ◽  
The Impact

ABSTRACT We report a remarkable overdensity of high-redshift submillimetre galaxies (SMG), 4–7 times the background, around a statistically complete sample of twelve 250 μm selected galaxies at z = 0.35, which were targeted by ALMA in a study of gas tracers. This overdensity is consistent with the effect of lensing by the haloes hosting the target z = 0.35 galaxies. The angular cross-correlation in this sample is consistent with statistical measures of this effect made using larger sub-mm samples. The magnitude of the overdensity as a function of radial separation is consistent with intermediate scale lensing by haloes of the order of $7\times 10^{13}\mbox{ $\rm M_{\odot }$ }$, which should host one or possibly two bright galaxies and several smaller satellites. This is supported by observational evidence of interaction with satellites in four out of the six fields with SMG, and membership of a spectroscopically defined group for a fifth. We also investigate the impact of these SMG on the reported Herschel fluxes of the z = 0.35 galaxies, as they produce significant contamination in the 350 and 500 μm Herschel bands. The higher than random incidence of these boosting events implies a significantly larger bias in the sub-mm colours of Herschel sources associated with z < 0.7 galaxies than has previously been assumed, with fboost = 1.13, 1.26, 1.44 at 250, 350, and 500 μm . This could have implications for studies of spectral energy distributions, source counts, and luminosity functions based on Herschel samples at z = 0.2–0.7.

scholarly journals Local starbursts seen when the Universe was 2–4 Gyr old

2009 ◽  
Vol 5 (S266) ◽  
pp. 499-499
Author(s):  
S. M. Petty ◽  
D. F. de Mello ◽  
J. P. Gardner ◽  
J. S. Gallagher
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Rest Frame ◽  
Formation Rate ◽  
Starburst Galaxies ◽  
Spectral Energy ◽  
Multiple Star ◽  
Star Forming ◽  
The Galaxy ◽  
The Universe

AbstractWe explore the multiwavelength properties of three nearby starburst galaxies: NGC 3079, NGC 7673, and Mrk 08. We established that each of these galaxies has similar rest-frame far-ultraviolet (FUV) morphologies as Lyman-break galaxies (LBGs) at z ~ 1.5 and 4, when the age of the Universe was ~ 4.3 and ~ 1.6 Gyr, respectively. LBGs are at an important stage in galaxy evolution when the Universe had a peak in the star-formation-rate density. Many LBGs are primarily composed of star-forming clumps, i.e., stellar clusters, with a significant lack of older stellar populations. Here, we present the comparison of the spectral-energy distributions (SEDs) of three nearby starburst galaxies with those of typical LBGs. From our nearby sample, each object has been artificially redshifted to observe what the galaxies would look like at z ~ 1 to 4 in the rest-frame FUV. NGC 3079 is an edge-on Seyfert 2 galaxy. It has a bright bulge and is interacting with two other galaxies, with extended Hi only along NGC 3079. The redshifting process changes its appearance, so that at high z it looks like a chain galaxy with multiple knots of star formation and no bulge. NGC 7673 has extended Hi and the star formation is mostly within the inner optical region in the multiple star-forming clumps defining the galaxy morphology. In the FUV, the galaxy looks highly compact with little detail resolved. As it is artificially redshifted, the galaxy continues to look more spherical. Mrk 8 is a merging pair, with the two galaxies observable in the visible spectrum. It is classified as a Wolf–Rayet galaxy, which suggests a very young burst, and is composed of several large star-forming regions. The FUV image does not resolve the separate galaxies, and the appearance remains similar for each redshift. We use the Gini coefficient, M20, and the Sérsic index to quantify the morphologies. The SEDs of the objects have similarities with LBG stellar population models. Because these local galaxies can be studied in more detail, they act as a bridge between nearby observations of starburst galaxies and high-z starburst galaxies such as LBGs.

scholarly journals An empirical approach to the extragalactic background light from AEGIS galaxy SED-type fractions

2011 ◽  
Vol 7 (S284) ◽  
pp. 442-445
Author(s):  
Alberto Domínguez
Keyword(s):  
Galaxy Evolution ◽  
Direct Measurement ◽  
Spectral Energy ◽  
Intensity Level ◽  
Energy Distributions ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Luminosity Functions ◽  
Novel Method ◽  
Γ Ray

AbstractThe extragalactic background light (EBL) is of fundamental importance both for understanding the entire process of galaxy evolution and for γ-ray astronomy. However, the overall spectrum of the EBL between 0.1 and 1000 μm has never been determined directly, neither from observed luminosity functions (LFs), over a wide redshift range, nor from any multiwavelength observation of galaxy spectral energy distributions (SEDs). The evolving overall spectrum of the EBL is derived here utilizing a novel method based on observations only. It is emphasized that the local EBL seems already well constrained from the UV up to the mid-IR. Different independent methodologies such as direct measurement, galaxy counts, γ-ray attenuation and realistic EBL modelings point towards the same EBL intensity level. Therefore, a relevant contribution from Pop III stars to the local EBL seems unlikely.

scholarly journals Recent star formation in intermediate redshift (0.35< z <1.5) early–type galaxies

2012 ◽  
Vol 10 (H16) ◽  
pp. 132-132
Author(s):  
M. J. Rutkowski ◽  
H. Jeong ◽  
S. Yi ◽  
S. Kaviraj ◽  
S. H. Cohen ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Hubble Space Telescope ◽  
Spectral Energy ◽  
Observational Constraints ◽  
Wide Field ◽  
Early Type ◽  
Energy Distributions ◽  
Near Ir ◽  
Intermediate Redshift

AbstractWe measured the UV-optical-near-IR spectral energy distributions (SEDs) of redshift z ~ 0.3-1.5 early-type galaxies (ETGs) with the Hubble Space Telescope (HST) Wide Field Camera 3 (Rutkowski et al.2012). We searched for young stellar populations and morphological signatures of the mechanisms driving recent star formation (RSF) in these ETGs in order to provide observational constraints on models of galaxy evolution.

scholarly journals From the far-ultraviolet to the far-infrared – galaxy emission at 0 ≤ z ≤ 10 in the shark semi-analytic model

2019 ◽  
Vol 489 (3) ◽  
pp. 4196-4216 ◽  
Author(s):  
Claudia del P Lagos ◽  
Aaron S G Robotham ◽  
James W Trayford ◽  
Rodrigo Tobar ◽  
Matías Bravo ◽  
...  
Keyword(s):  
Rest Frame ◽  
Spectral Energy Distribution ◽  
Empirical Relation ◽  
Far Infrared ◽  
Initial Mass Function ◽  
Spectral Energy ◽  
Analytic Model ◽  
Star Forming ◽  
Wide Range ◽  
Far Ultraviolet

ABSTRACT We combine the shark semi-analytic model of galaxy formation with the prospect software tool for spectral energy distribution (SED) generation to study the multiwavelength emission of galaxies from the far-ultraviolet (FUV) to the far-infrared (FIR) at 0 ≤ z ≤ 10. We produce a physical model for the attenuation of galaxies across cosmic time by combining a local Universe empirical relation to compute the dust mass of galaxies from their gas metallicity and mass, attenuation curves derived from radiative transfer calculations of galaxies in the eagle hydrodynamic simulation suite, and the properties of shark galaxies. We are able to produce a wide range of galaxies, from the z = 8 star-forming galaxies with almost no extinction, z = 2 submillimetre galaxies, down to the normal star-forming and red-sequence galaxies at z = 0. Quantitatively, we find that shark reproduces the observed (i) z = 0 FUV-to-FIR, (ii) 0 ≤ z ≤ 3 rest-frame K-band, and (iii) 0 ≤ z ≤ 10 rest-frame FUV luminosity functions, (iv) z ≤ 8 UV slopes, (v) the FUV-to-FIR number counts (including the widely disputed 850 μm), (vi) redshift distribution of bright $850\, \mu$m galaxies, and (vii) the integrated cosmic SED from z = 0 to 1 to an unprecedented level. This is achieved without the need to invoke changes in the stellar initial mass function, dust-to-metal mass ratio, or metal enrichment time-scales. Our model predicts star formation in galaxy discs to dominate in the FUV-to-optical, while bulges dominate at the NIR at all redshifts. The FIR sees a strong evolution in which discs dominate at z ≤ 1 and starbursts (triggered by both galaxy mergers and disc instabilities, in an even mix) dominate at higher redshifts, even out to z = 10.

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