| 4C +41.17 | |
|---|---|
 4C +41.17 captured byW. M. Keck Observatory | |
| Observation data (J2000.0epoch) | |
| Constellation | Auriga |
| Right ascension | 06h 50m 52.09s |
| Declination | +41d 30m 30.53s |
| Redshift | 3.792000 |
| Heliocentric radial velocity | 1,136,813km/s |
| Distance | 11.665 billionGly (light travel time distance) |
| Apparent magnitude (V) | 0.344 |
| Apparent magnitude (B) | 0.455 |
| Surface brightness | 21.7 |
| Notable features | Radio galaxy,starburst galaxy,luminous infrared galaxy |
| Other designations | |
| INTREF 315,PGC 2820698,NVSS J065052+413027,6C B064720.6+413402,7C 0647+4134, TXS 0647+415, B3 0647+415, SMM J065052.1+413030 | |
4C +41.17 is aradio galaxy located in the constellationAuriga. With theredshift of 3.79, it is located nearly 11.7 billionlight-years fromEarth.[1] At the time of its discovery in 1988,[2] it was one of themost distant galaxies ever seen.[3][4]
4C +41.17 is classified as one of thelargest radio galaxies in theearly universe withemission atKs spread nonuniformly over a 3× 6 (42× 84 kpc) area.[5][6] A potentiator of a massiveelliptical galaxy located in the center of low-redshiftgalaxy cluster,[7] it hosts a powerfulradio source with a high-powered (1046 ergs/s)astrophysical jet that is producing shock-excited emission-linenebulosity through its 1000 km/s shocks. With a C IV luminosity emanating from the shock, this implies the preshock density in the line-emitting cloud is high as it contains ahydrogendensity of 110 cm−3. This causes shock-initiated star formation proceeding on a timescale (a few × 106 yr) within estimateddynamical age (3 × 107 yr) of the radio source.[8][9]
4C +41.17 is ahyperluminous infrared galaxy, with astar formation rate of >103 Msolar yr-1, making it a strong candidate for being a primeval galaxy, in the process of a major episode of star formation.[10] With radioluminosity ofL500 MHz > 1027 W Hz−1,[11] 4C +41.17 is an extremely rare object that has anumber density of ~10−8 Mpc−3 in the redshift range 2 <z < 5.[12]
With characteristics like having a steepradio spectrum of (α ~ −1.3) together with an extendedoptical continuumemission and largerest frameLyα equivalentwidth of ~270 Å, this identifies 4C+41.17 as a high redshift radio galaxy. It has a highinfrared luminosity ofLFIR ~ 1013 L⊙[13] with large dustmass located in thedust lane in the center of the galaxy[14] andmolecular gas reservoir, making it a site of star production.
From theinterferometer used atIRAM 30m telescope inSpain, researchers detected twocarbon oxide (CO) systems in 4C +41.17. These systems are measured by M_dyn ~ 6 × 1010 M⊙ which is separated by 1\farcs8 (13 kpc), and 400\kms invelocity. The carbon oxide systems then coincide with two different dark lanes in a deep Lya image. One of the CO component is found to coincide with the cm-radio core of 4C +41.17, with a close redshift to the \HeII AGN line. The second component is located near the base of acone-shaped region that is southwest of the nucleus, resemblingemission-line cones seen in nearbyactive galactic nuclei andstarburst galaxies. The characteristics of the CO sources and their mm/submm dust continuum are similar to those found inultraluminous infrared galaxies and in some high-z radio galaxies andquasars. The fact that 4C 41.17 contains two CO systems is a sign that it might have gone a merger with anothergalaxy.[15]
There is also a strong presence of strongX-ray emission originating from apoint source that is coincident with the nucleus. According to researchers, an extended X-ray emission is found having a luminosity of ~1045 ergs/s. The emission covers 100 kpc (15″)diameter region which it surrounds the radio galaxy, and follows the general distribution pattern of radio emission in the radio lobes of this source and the giant Lyα emission-line halo distribution. However, the spectrum of the X-ray emission on the other hand, isnonthermal with apower-law index consistent to a radiosynchrotron. This signifies the X-ray emission is most likely an inverseCompton scattering ofphotons that are far-infrared from a relativistic electron population associate with past and current activity from the central object.[16]
4C +41.17 was also observed byHerschel, which about 65% of the extracted sources at 70, 160, 250, 350 and 500micron, are identified as mid-infrared sources that were observed throughSpitzer Space Telescope at 3.6, 4.5, 5.8, 8 and 24 micron. From these observations, the Herschel sources are mostly foreground towards radio galaxy and therefore not belong to any structure associated with the galaxy.[17]
Hubble Space Telescope did observe 4C +41.17 through detections using goodsignal-to-noise ratio with a spatially resolution of 0.1" (440 pc); this suggests 35% of this emission ends up in the form of a high brightness clumpy regions extending by about 0.5" (1.7 kpc). Thismorphology is remarkably similar to that of the radio components. A fainter diffuse region of optical emission is seen extending westward from the center of the nuclear complex about 1.2" (5.3 kpc) out along the radio axis, indicating the emission of stellar origin with an estimated mass of about 10^10^M_sun_ of stars in each <= 500 pc clump.[18]
Deepspectropolarimetricobservations via theW. M. Keck Telescope conducted by researchers inHawaii, finds out that 4C +41.17 isunpolarized between ʎrest ~ 1400 Å2000 Å. This indicates scattered light has no dominance over the alignedultraviolet continuum. Instead, they found that 4C +41.17 showabsorption lines and features ofP Cygni similar to those seen inz ≈ 2–3 star-forming galaxies and nearby starburst systems containingWolf-Rayets. It is possible that galactic outflow partially contributes to absorption-line profiles but unlikely for the high-velocity wings of the high ionization lines being dominated by throughgalactic winds since there is large outflow mass implied by the absorption line strengths.[19]
Through the detection of S V λ1502 stellarphotospheric absorption line, the shape of blue wing of the Si IV profile, unpolarized continuum emission, the inability of any active galactic nuclei-related processes accounted for the ultraviolet continuumflux, and similarity of the UV continuum spectra of 4C 41.17 overall as well as the nearby star-forming regionNGC 1741B1, these characteristics strongly suggest that ultraviolet light from 4C 41.17 is dominated by young, hotstars, in which its star formation rate is roughly 140-1100 h-250 M⊙ yr-1.[19]
4C +41.17 is located in the center of a largeLyman-alpha halo. Such penetrations of jets through itsgalactic halo causes substantial jet to cloud interactions. In this case of the jet-cloud interaction evident near the radio knot B2 in 4C +41.17, researchers suggested a glancing incidence of the jet causes a partialbow shock, that is driven into towards the cloud. This is manifest through associated shock-excited line emission and associated star formation in thebifurcated structure. The jet then deposits much of itsmomentum at the site, before continuing onward to the next knot B3 where decelerated jetplasma is accumulated asradio lobes.[8]
A deeper observation shows there are three distinct components in 4C +41.17. The emission-line gas is made up of made up of two components which are associated with the other components B1, B2, and B3 of the inner radio source. They are relativelynarrow lines containing Lyman-alpha, silicon andhelium withFWHM of 500,650 km/s, and a broad Lyman-alpha andchromium with FWHM 11,001,400 km/s. The third component consists of narrow absorption lines often associated with the narrow emission lines in P Cygni. This lines have FWHM 400,800 km/s.[8]
Most observed narrow emission lines are usually produced either in the jet bow shock or in the photoionized winds from newly formed stars, but with an exception ofcarbon group IV elements likecarbon, silicon,germanium,tin, andlead. Such of these elements are found weaker in older stars than 3 × 106 yr. The C IV emission is narrower indicating most of the flux originates in the precursor material that is ahead of bow shock. This is consistent with the velocity of 1000 km/s that researchers adopted for the normal component of the shock. For velocity shocks, almost all of the C IV emission originates from the precursor.[20]
The cloud mass in 4C +41.17 is found to be 3.4 kpc wide. It has an area equal to the entire Ly-alpha bright region adjacent to B2 region measuring 65 kpc2. This means a mass of ≈ 8 × 1010f(C IV)M○. This cloud mass indicates that star formation occurs within the galaxy as a result ofgravitational collapse. The free-fall time for the clouddensity is estimated to betff ≈ 2100-1/2 ≈ 1.4 × 107 (nh/10 cm−3)-1/2 that is comparable to thedynamical timescale of the radio source in 4C +41.17 itself.[8]
